Human adenovirus (HAdV) is the most common cause of infection to the ocular surface, accounting for up to 75% of conjunctivitis cases.1 The most common presentation is pharyngoconjunctival fever (PCF), which often occurs in children and manifests clinically with fever, pharyngitis, rhinitis, follicular conjunctivitis, and regional lymphoid hyperplasia.2 Epidemic keratoconjunctivitis (EKC) is the most severe ocular form and is distinguished by its ability to invade the corneal epithelium, ranging in presentation from a keratitis to persistent and recurrent subepithelial infiltrates (SEIs). HAdV is highly contagious due to its unique structure and ability to evade the normal host’s immune system. It is distinguished from other types of conjunctivitis in that it often involves the cornea, with potentially devastating visual complications. These features contribute to a heavy economic burden and necessitate the establishment of a standard treatment protocol.1 In addition to the potential ocular manifestations of this virus, HAdV infections have the propensity to manifest systemically, in cases such as respiratory, urinary, and gastrointestinal tract (GIT) infections. This variety of presentations can infect a normal, healthy host, and also have an increased risk in immunocompromised individuals. Despite the detrimental effect that HAdV infections pose, there has yet to be an FDA-approved drug to treat these conditions, making management difficult. Even following the active phase of the disease, viral persistence and reactivation may occur. Oral and topical antivirals have been considered as off-label management solutions, but problems with efficacy, bioavailability, and therapeutic profiles have limited their use. With regards to EKC, topical disinfection during active cases as well as treatment of corneal sequelae using corticosteroids and immunosuppressive agents show promise. This review will focus on how persistence and dissemination of HAdV poses a significant challenge to the management of adenoviral keratoconjunctivitis. Furthermore, current and future trends in prophylactic and therapeutic modalities for adenoviral keratoconjunctivitis will be discussed.

Surgical management is usually not required in adenoviral keratoconjunctivitis; however, it may be necessary in cases of significant fibrotic remodeling of the conjunctiva or sustained corneal scarring with visual consequence. Membranes that develop on the mucosal surface can be differentiated into pseudomembranes or true membranes, with the latter being clinically distinguished by induced bleeding upon denuding.1

Persistence of pseudomembrane can lead to subepithelial fibrosis of the conjunctival mucosa, symblepharon formation, and punctal occlusion.1 Thus, rare cases may require repair of the fornix and associated lid anatomy defect (entropion or ectropion). Furthermore, streptococcal co-infection may be present in severe cases, with membranes that can precipitate corneal perforation and necessitate treatment.95

For patients with chronic adenoviral corneal opacification following resolution of acute infection, phototherapeutic keratectomy (PTK) can be an alternative option to other corneal surgeries or transplants. Corneal transparency can be compromised, or corneal irregularity may result with sequelae from the immune response to pathogen. Fortuitously, these scars are often superficial in nature by virtue of affecting the subepithelial layer. Transepithelial PTK low dose mitomycin C has shown benefit in such cases with reported improvements in photophobia, best corrected vision, and contrast sensitivity.96 Furthermore, a decrease in coma, secondary astigmatism, and total higher-order aberrations have been noted after PTK for SEIs in adenoviral keratoconjunctivitis.97

Vernal keratoconjunctivitis (VKC) is a bilateral, chronic sight-threatening ocular disease which usually occurs in patients under 20 years of age.[1,2] VKC has a wide geographical distribution and is commonly found in warm, dry areas.[3,4] Patients with VKC usually present with eye irritation, itching, redness, tearing, pain, and blurred vision.[5] The etiology of VKC is still unclear, but a Th2-mediated allergic mechanism thought to be involved in the pathogenesis of the disease.[6] VKC can result in permanent decrease or loss of vision if treatment failed.[7,8] To achieve good treatment outcomes, long duration of drug treatment combined with living habit adjustment is needed. There are numerous topical drugs used in VKC treatment, such as vasoconstrictors, mast-cell stabilizers, antihistamines, nonsteroidal antiinflammatory agents, corticosteroids, and immunomodulators.[9] These drugs reduce signs and symptoms in the acute phase of VKC, but the therapeutic results are not satisfied.[10,11]

Recently, herbal medicine becomes an alternative therapy for numbers of diseases. Houttuynia, a traditional Chinese herb primarily found in China, Japan, Korea, and Southeast Asia, has been used for the treatment of various disease for hundreds of years.[12,13] The main active components of Houttuynia are flavonoids, flavonoid glycosides, ionones, and some alkaloids.[14] Houttuynia extracts are proved to have antibacterial, antiallergic, antiinflammatory, and antioxidative effect.[12,15–17] It is reported that Houttuynia eye drops (HED) can achieve good effect in the treatment of VKC.[18] However, there is no systemic review and meta-analysis published regarding the clinical efficacy of HED. Here we plan to run a systemic review and meta-analysis of randomized controlled trials (RCTs) to assess the efficacy of HED for the treatment of VKC.

Only RCTs will be included in this study.

The ocular manifestations of viral infections in neonates and children vary greatly and can range from innocuous to vision threatening (73). The majority of viral conjunctivitis in children are caused by adenovirus, a DNA virus, which can cause a range of human diseases, including upper respiratory tract infection. Viral conjunctivitis is associated with epidemic keratoconjunctivitis, pharyngoconjunctival fever and acute haemorrhagic conjunctivitis (74). Signs include eyelid oedema and tender pre-auricular lymphadenopathy, prominent conjunctival hyperaemia, follicles and punctate epithelial keratitis. In viral infections in children, the involvement of the anterior segment is mild and self-limited; spontaneous resolution usually occurs within 2–3 weeks, except in cases of congenital infection, which are often associated with significant alterations in ocular structures.

Neonatal conjunctivitis (also known as ophthalmia neonatorum) is defined as conjunctival inflammation developing within the first month of life. It is the most common type of infection in neonates, occurring in up to 10% of neonates. It is often identified as a specific entity distinct from conjunctivitis in older infants as it is often the result of infection transmitted from the mother to the infant during delivery (74). Molluscum contagiosum ocular infection in children is caused by a specific double-stranded DNA poxvirus, which typically affects otherwise healthy children with a peak incidence between the ages of two and four. Transmission occurs through contact, with subsequent autoinoculation. Presentation is with chronic unilateral ocular irritation and mild discharge, while lesions are usually self-limiting. Primary infection with herpes simplex virus (HSV) is usually associated with eyelid and periorbital vesicles, papillary conjunctivitis, discharge and lid swelling. Dendritic corneal ulcers can also be present, particularly in patients with atopic infection can lead to eczema herpeticum, which can be very severe (75–77). Varicella-zoster virus (VZV) is a serious, but rare, viral infection in children, in which prolonged inflammation may lead to corneal thinning or perforation, glaucoma and cataract formation (74).

Involvement of the posterior structures mostly related to HSV and VZV is potentially sight-threatening. Retinal or optic nerve involvement should be suspected in any child, who complains of an acute onset of blurred vision in the absence of anterior segment inflammation or opacities in the ocular media. Optic neuropathy may occur as an isolated sign, although it is more often associated with a more generalised involvement of the central nervous system (77,78). While specific therapy is not always available, the early diagnosis of ocular viral disease in children should aid in the amelioration of acute symptoms and in the prevention of long-term complications.

Conjunctivitis, a common ocular condition with a range of etiologies, is highly prevalent, affecting approximately 6 million people annually in the United States and accounting for 1% of all primary care office visits. Viruses are responsible for up to 80% of conjunctivitis, and human adenoviruses (HAdVs) are implicated in up to 65% of all viral cases. Adenoviruses are small, non-enveloped viruses with a linear, double-stranded DNA genome of approximately 36 kilobase pairs. The seven species (A-G) and more than one hundred genotypes currently in GenBank exhibit a broad range of tropisms across the various mucosal surfaces of the body, including those within the respiratory, gastrointestinal, and genitourinary tracts, in addition to cells on the ocular surface. While adenovirus infections are generally acute and self-limiting in immunocompetent patients, they can be fatal in children and immunocompromised individuals.

The most severe adenovirus infections of the ocular surface are associated with HAdVs of species D (HAdV-D), the species with the largest number of described viruses. The term “ocular surface” broadly refers to the cornea and the conjunctiva (Figure 1). The principal function of the cornea is to refract incoming light to the lens, where the light is then focused onto the retina for visual discrimination. The cornea is composed of five distinct layers (from anterior to posterior): the epithelium, Bowman’s layer, stroma, Descemet’s membrane, and endothelium. The stroma, sometimes called the corneal substantia propria, accounts for approximately 85% of the total corneal thickness and houses a large population of keratocytes and a small number of corneal resident immune cells. The conjunctiva is the mucus membrane that lines the inside of the eyelids and covers the globe. It consists of an outer three to five cell layers thick epithelium of stratified squamous and columnar epithelial cells interspersed with goblet cells. It also contains blood vessels, lymphatic channels, and numerous immune cells, including T and dendritic cells. The conjunctival substantia propria is its deeper layer, and is rich in connective tissue, lymphocytes, mast cells, plasma cells, and occasionally neutrophils in the normal conjunctiva.

Perhaps due to the relatively self-limiting nature of most conjunctivitis presentations, in which symptoms usually resolve within two to three weeks of onset, very few studies have investigated conjunctival immune responses to virus infection. Clinically, however, ocular HAdV infection generally presents as one of three highly contagious syndromes: follicular conjunctivitis, pharyngoconjunctival fever (PCF), or epidemic keratoconjunctivitis (EKC). Follicular conjunctivitis is characterized by bulbar conjunctival injection and chemosis, follicular hyperplasia, preauricular adenopathy, and sometimes conjunctival petechiae or frank subconjunctival hemorrhages. PCF appears similar, however, in addition to the ocular signs, is associated with a systemic, flu-like illness. EKC, which is most commonly caused by HAdV-D8, -37, -53, -54, -56, and -64, is a severe, hyperacute, and particularly contagious infection. EKC is characterized by acute membranous keratoconjunctivitis and delayed-onset subepithelial corneal infiltrates (SEIs) (Figure 2).

SEIs, the hallmark feature of EKC, occur in approximately one-third of all EKC cases and may persist or recur for months to years following infection. SEIs impair vision by physically blocking the passage of light and by disrupting the arrangement of collagen fibrils and other extracellular matrix components of the meticulously organized and normally transparent corneal stroma. Clinically, this manifests as reduced vision, foreign body sensation, and photophobia. Based on both experimental and clinical evidence, SEIs form as a consequence of infiltrating leukocytes, recruited from the corneal limbus to the superficial corneal stroma. SEI appearance is delayed by up to three weeks from the onset of infection, a time when active viral replication has ceased, which suggests that long term morbidity associated with infection is immune-mediated rather than a result of virus-associated tissue damage. Unfortunately, despite frequent outbreaks of adenoviral conjunctivitis and the substantial economic impacts—due to lost work time and expenses associated with medical visits and diagnostic testing—there are currently no specific antiviral therapies for adenovirus ocular infections. Further, due to their apparent immunological origin, SEIs are unresponsive to direct-acting antivirals. The elucidation of the immunopathogenesis of infection and its relationship with the virus replication cycle is crucial to the potential development of future immunomodulatory therapies.

Dogma maintains that HAdVs enter host cells via dynamin-dependent, clathrin-mediated endocytosis before trafficking along microtubules to the nucleus for replication. However, recent work has demonstrated that adenoviruses utilize several entry mechanisms, including macropinocytosis and caveolin-mediated pathways. The specific mechanism of entry appears to depend most on the specific pairing of cell and virus type. In some cell types, viruses may exploit more than one pathway with no apparent preference. Furthermore, a predominant pathway may be supplanted by another pathway if the former is blocked. Redundancy in both entry and subsequent immune responses may be the rule rather than the exception. Furthermore, analyses of viral entry may be complicated by the finding that some host signaling proteins that were initially identified as specific to a particular pathway are in fact shared by disparate pathways.

Innate immune responses to adenoviruses rely on the detection of pathogen-associated molecular patterns (PAMPs): distinct ligands present on the external surfaces, and nucleic acids of pathogens (but absent in the host) that feature molecular signatures able to be recognized by pattern recognition receptors (PRR) on or in infected host cells. Due to the specific distribution of these PRRs on the cell surface, in endosomes, and in the cytosol, it is expected that adenoviruses utilizing disparate entry and trafficking mechanisms may stimulate specific and unique subsets of PRRs, ultimately resulting in unique immune response signatures. Consistent with this hypothesis, it was shown that rapidly trafficking adenoviruses replicate more efficiently, but may not stimulate host cytokine responses as effectively as a virus that enters and traffics more slowly. However, such a relationship has yet to be fully defined in the context of ocular surface cells. This review will focus broadly on the mechanisms of adenoviral entry and trafficking, the immune responses to adenovirus infection of the ocular surface, and the possible connection between the two.

In the past few decades, highly sensitive and specific tests for virus detection have been developed, resulting in accurate detection of a long list of viruses associated with wheezing in early life, the risk for developing asthma, and exacerbation of established disease. Human rhinovirus (RV) and respiratory syncytial virus (RSV) top the list, but recently discovered or re-emerging viruses (e.g., human metapneumovirus [HMPV] coronaviruses and enterovirus [EV]-D68) also contribute to acute wheezing in infancy and virus-mediated exacerbations. However, most viral infections are not associated with acute exacerations, and cofactors, including allergic inflammation and airway bacteria, have been described that increase the severity of infection and the probability of exacerbation.12 Detection of both viruses and airway bacteria are associated with acute wheezing illnesses; specifically, co-infections of respiratory viruses and Moraxella catarrhalis, Hemophilus influenza, and/or Streptococcus pneumonia increases the risk for more severe respiratory illnesses and exacerbations of asthma.3 The addition of antibiotics to treatment regimens for asthma exacerbation could materialize in the near future.

Several recent studies have also shown that respiratory allergy may partner with certain viral infections to synergistically produce airway inflammation and increase cold and asthma symptoms.4 Since there is currently no safe and effective antiviral for RV, the targeting of allergic inflammation may prove beneficial in reducing risk of severe virus-induced asthma symptoms.5 There are several possible immunopathologic mechanism(s) that connect viral and bacterial infection, allergy, and acute asthma, as discussed in the following sections.

IM is the main clinical manifestation of Epstein Barr virus (EBV) infection (86). Other agents, such as CMV, toxoplasma and adenovirus, produce a similar illness. The incubation period ranges from 33 to 49 days (87). Clinical presentation is usually prolonged (average 16 days) and ranges from a non-specific flu-like illness to the more distinctive triad ‘fever, pharyngitis, lymphadenopathy-splenomegaly’. Other clinical manifestations include fatigue, hepatitis and eyelid oedema. Possible complications are meningoencephalitis, haemolytic anaemia, thrombocytopenia, rash, conjunctivitis, haemophagocytic syndrome, myocarditis, neurologic diseases, pancreatitis, parotitis, pericarditis, pneumonitis, psychological disorders and splenic rupture. Laboratory findings include the elevation of liver enzymes and lymphocytosis with a marked increase in the number of atypical lymphocytes in the peripheral blood (87). Additionally, immunophenotypic alterations of lymphocytes have been described in the various phases of EBV infection (88). More specifically, a reduction of B-lymphocytes and an increase in the number of CD3+CD8+, T-lymphocytes, with a subsequent decrease in the CD3+CD4+/CD3+CD8+ ratio is noted (89).

In the study by Panagopoulou et al (86), which was presented at the Workshop, researchers aimed to examine whether there is an association between the immunophenotypic alterations and the variability of the clinical presentation of IM. Although several studies (89–91) have examined the immunophenotype of lymphocytes in EBV infection, very few (89) have correlated these with the clinical course. The presented study (86) showed that the immunophenotypic analysis of cytotoxic T cells provides important information on the physiology of the immune response to EBV infection. Additionally, it may potentially play a predicting role, providing information on the expected clinical course, potential complications and the time to recovery from EBV infection.

Herpes simplex virus type 1 (HSV-1) is an enveloped double-stranded DNA virus belonging to the Herpesviridae family. This virus, a common human pathogen, is the main cause of oral infection, affecting the mouth and lips. In addition, HSV-1 can be the infectious agent of several diseases including recurrent cold sores, keratoconjunctivitis, and life-threatening herpes encephalitis. Following primary infection, HSV establishes infections in the neurons of the sensory ganglia from where it may become latent in the body. In the nervous system, the virus is protected from the host immune system as a latent state, which can be reactivated by several factors, such as hormonal changes, ultraviolet (UV) light, and mainly the stress. The treatment of infection caused by the HSV-1 include the use of drugs, such as acyclovir, valacyclovir, famciclovir, penciclovir, and cidofovirare. Some pharmacokinetic limitations of these drugs can be difficult because of their transport to affected tissues, inducing non-therapeutic drug levels. Moreover, long-term of these treatments may lead to the selection of resistant HSV, being an additional concern mainly for the immunocompromised patients, which has emphasized the need for alternative strategies.

Chloroquine diphosphate (CQ) is an antimalarial drug that has been used as the first-line treatment against Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, and Plasmodium falciparum infections. In addition to the antimalarial activity, CQ has been used to treat chronic diseases such as rheumatoid arthritis and systemic lupus erythematosus. Recently, this drug has also attracted attention due to its anticancer and antiviral activity. In this context, CQ is a hydrophilic drug with low toxicity that has shown some limitations to reach an effective intracellular concentration. One of the main disadvantages of the conventional malaria treatment is the non-specific targeting to intracellular parasites, which leads to high dose administration, resulting in toxicity.

As expected for antimalarial drugs, the efficacy of antiviral drugs such as CQ depends on their cellular uptake. In attempt to solve this limitation of CQ against HSV-1, the nanodrug delivery systems (NDDS) are known to change drug biodistribution, decrease toxicity, modify drug release rate, and mainly, drug targeting to affected tissues/cell. Among the NDDS, polymeric nanoparticles (NP) is a promising approach to improve drug uptake for a specific cell line. Their advantages include higher stability in biological fluids and easy storage conditions. Polyesters, such as poly(lactic acid) (PLA) are biocompatible and biodegradable polymers, which are completely eliminated from the body by natural metabolic pathways. Furthermore, PLA is a polymer approved by the Food and Drug Administration (FDA) that has been widely used as a biomaterial for the preparation of nanoparticles for drug delivery.

Several methods have been applied to prepare NP. They can be divided into two categories: Those based on the dispersion of preformed polymers and those based on the polymerization of monomers. Considering the dispersion of preformed polymers, the solvent evaporation method or the spontaneous emulsification/solvent diffusion method is a well-consolidated one. Nanoprecipitation (solvent displacement method) is a one-step procedure controlled by the interfacial deposition of the polymer after its displacement from organic to aqueous phase. Due to the fast spontaneous diffusion, nanoparticle formation occurs instantaneously. Emulsification-solvent evaporation method is a two-step procedure in which the organic solution is emulsified in the aqueous phase using a high-speed homogenization or ultrasonication. The formation of NP occurs due to the polymer precipitation after the solvent evaporation.

The entrapment of hydrophilic drugs inside hydrophobic polymeric nanoparticles is not an easy task, especially when using the nanoprecipitation method. Indeed, hydrophilic drugs have weak interactions with polyesters, such as PLA. Thus, the drug transport from the organic phase to the outer aqueous phase induces low entrapment efficiency. This phenomenon justifies drawbacks of less-well protected drug from degradation and a faster drug release. Some strategies have been used to improve the encapsulation efficiency of hydrophilic molecules in polyester nanoparticles. Controlling pH of aqueous phase, changes in the solvent phase, use of high drug concentration, and salt addition in the aqueous phase are some examples.

In the context of anti- HSV-1 activity of CQ, a specific study reported by Singh et al. (1996) demonstrated the possible mechanism of action of CQ as a promising antiviral drug. This drug has a character of weak base that contributes to increase the intracellular pH, affecting the virus life cycle. In addition. CQ impairs the gD protein transport from trans-Golgi network to cell membrane, which induces the formation of defective viral particles. Thus, this study was performed to improve the encapsulation efficiency of hydrophilic CQ into biocompatible PLA nanoparticles, and to evaluate how the modulation of the drug release affects its anti-HSV activity. The experimental design included different preparation methods, variation in the polymer/drug ratio, and specific parameters such as pH of aqueous phase. The anti-HSV performance was assessed using Vero E6 cells.

Acute respiratory infections in humans are usually ascribed to one or more of a group of well known viruses, including more than 100 rhinoviruses (“common cold” viruses), influenza viruses A and B, parainfluenza viruses, corona viruses, respiratory syncytial virus, and certain adenoviruses. In addition the recent application of more sensitive molecular detection techniques has revealed the presence of other viruses, such as metapneumoviruses and bocaviruses, which might also be involved in the generation of respiratory symptoms. However we do not know if these newly recognized viruses are really pathogenic, or are simply “passengers” that eluded previous diagnostic techniques. Nevertheless various families of viruses, with different structures and replication schemes, and consequently bearing different potential molecular targets, are clearly involved in respiratory symptoms, as indicated in Table 1. Among the possible targets are: (i) the virion itself; (ii) cellular attachment or entry; (iii) one or more of the many stages in virus replication and development, particularly those that involve virus-specific enzymes; (iv) egress of progeny virus from infected cells. However the variety of replication schemes indicated in Table 1 reduces the chances that a single antiviral drug could target many of these viruses. In addition, in the majority of respiratory infections specific virus information is lacking; consequently it is difficult to conceive of a single therapeutic agent or regimen that could control the “causative agent”. Nevertheless, in spite of this limitation, considerable time and money has been spent trying to find the “silver bullet” for specific virus “infections”, so far without much success.

Another problem with the specific target approach, especially in the case of compounds directed at specific viral genes or their products, is the inevitable emergence of virus resistant mutants and their subsequent spread through the community and environment. The conventional answer to this problem has been the suggestion that two or more antiviral drugs, with distinct molecular targets, be used in combination, notwithstanding the likely increase in undesirable side-effects. A logical alternative approach is the use of a non-toxic agent that has the capacity to inhibit many different respiratory viruses simultaneously, and recent evidence indicates that certain herbal extracts might fulfill this requirement.

Adenoviruses are ubiquitous, non-enveloped, double-stranded DNA viruses. Human adenoviruses (HAdVs) are classified into 7 species (Human mastadenovirus A to G) and at least 69 recognized genotypes based on serology, whole-genome sequencing, and phylogenetic analyses. The prevalence of different HAdV types varies among different geographical regions. HAdVs have been recognised as pathogens that cause a broad spectrum of diseases [1, 2], including acute respiratory infection (ARI), gastroenteritis, conjunctivitis, cystitis, and meningoencephalitis. ARI is prevalent in children, and is one of the most common causes of morbidity and mortality in the paediatric population in developing countries [3, 4]. Numerous outbreaks of ARI caused by HAdV have been reported during the last decade in many countries including China [5–14]. The HAdV types most commonly found in respiratory samples belong to HAdV-C (HAdV-1, -2, -5, -6) and HAdV-B (HAdV-3, -7) [2, 10–15]; however, severe or even fatal disease outbreaks are predominantly caused by only a few types (such as HAdV-14, -21 and -55) [2, 5–9]. The molecular typing by HAdV hexon sequences can help to accelerate the discrimination of types, resulting in timely epidemiological examinations and improved patient care [16–20]. Several studies have shown the association between severe respiratory infections in adult and HAdV species [7–9]; however, reports among children with severe acute respiratory infection (SARI) in China are limited.

The purpose of this study was to determine the prevalence and genotype (sequencing of the hexon gene after polymerase chain reaction [PCR] screening) of HAdVs among children with SARI in different areas of China from 2007 to 2010. HAdV infections are often associated with the co-infection of bacterial or viral agents, frequently leading to severe clinical consequences in hospital patients. Thus, co-infection with other respiratory viruses of HAdV was also investigated.

Asthma and COPD are prevalent chronic pulmonary diseases characterized by chronic airway inflammation and airflow limitation. The differences between the two diseases are mainly the cellular and molecular features of airway inflammation and the degree of reversibility of airway flow limitation. Generally, reversibility of airflow limitation is incomplete in COPD, while that in asthma can be complete. Airway inflammation in asthma is characterized by allergic phenotypes, such as dense infiltration of eosinophils and T helper type 2 lymphocytes, associated with atopic status, while that of COPD is mainly accumulation of neutrophils, CD8-positive cytotoxic T cells, and activated macrophages, which are caused by inhalation of harmful substances, such as smoking. With respect to the site of inflammation, asthma involves predominantly larger airways, while in COPD, inflammation affects predominantly small airways and the lung parenchyma, characterized as irreversible airway narrowing because of fibrosis around the small airways or destruction of alveolar walls with protease-mediated degradation (Barnes, 2008). Of note, neutrophilic infiltration could be recognized in bronchial biopsied specimens as well as eosinophils in severe refractory asthma (Wenzel et al., 1999).

Herpes simplex virus-1 is a double stranded DNA virus associated with chronic infections in humans [1, 2]. HSV-1 infections may result in serious morbid, potentially mortal, conditions. HSV-1 corneal infections may cause herpes stromal keratitis (HSK), a condition that may advance to corneal opacity and blindness [1–3]. In fact, HSV-1 represents the leading infectious cause of corneal blindness worldwide [3, 4]. HSV-1 utilizes various pathways and strategies for entry into host tissues, including the cornea [3, 4], from which it may disseminate into the nervous system causing a lethal condition, herpes encephalitis [1–5]. Additionally, HSV-1 may cause severe neonatal infections [1, 5].

Macroautophagy (hereafter referred to as autophagy) is a catabolic cellular process, aimed at degradative removal of certain cytoplasmic components (proteins, or organelles) of the cell, or intracellular pathogens [6–10]. The autophagy pathway involves sequestration of a part of the cytosol inside isolation membranes. These membranes give rise to autophagosomes (double-membrane vesicles compartments), which then fuse with the lysosomes for cargo destruction [6–10]. Numerous stimuli trigger autophagy, such as starvation, hypoxia, hormones, certain drugs, and some infections [8–10].

In HSV-1 infection, induced autophagy responses were shown to lower the virulence of the virus in vivo [11, 12], and limit its replication in vitro [12, 13]. The ability of autophagy to degrade HSV-1 particles was also suggested. Such findings stress the importance of understanding how the virus may regulate the autophagic response of the host to infection. It was previously suggested that the HSV-1 neurovirulence gene product ICP34.5 suppresses autophagy levels in the host by binding to the autophagy protein beclin1 [11, 13, 14]. Other studies, however, reported that HSV-1 infection can also induce autophagy [15, 16]. However such a response was only reported at high multiplicities of infection (MOIs) [15, 16]. Accurate autophagy analysis and interpretation are complicated by numerous factors, such as assay limitations [17–19], cell type specific effects [20, 21], and infection conditions including virus strains, multiplicities of infection (MOIs), and time point post-infection [11, 13–16]. These factors collectively urged us to further elucidate HSV-1-mediated regulation of autophagy.

In this study, we determined HSV-1-regulated autophagy levels of the host cells under various productive infection conditions. Interestingly, we found that autophagy may be inhibited or may remain unchanged significantly in most cell types tested. These results help attain a comprehensive, more accurate understanding of virus-mediated regulation of autophagy.

Asthma and chronic obstructive pulmonary disease (COPD) are very common inflammatory diseases of the airways. The World Health Organization (WHO) estimates that asthma accounts for 1 in every 250 deaths worldwide (O’Sullivan, 2005). The prevalence of asthma in developed countries is approximately 10% in adults and even higher in children, while in developing countries, the prevalence is lower but increasing rapidly (Barnes, 2008). In the case of COPD, WHO consensus reports forecast that this disorder will be ranked the third cause of mortality in the world by 2020 (Global initiative for chronic obstructive lung disease [GOLD], 20131). Acute deterioration of symptoms and lung function, which often results in respiratory failure, is a so-called “exacerbation,” and it is an important and severe social and medical burden in both diseases.

Respiratory viral infections are common and usually self-limiting illnesses in healthy adults and a major cause of exacerbations in patients with asthma (Figure 1) and/or COPD (Figure 2).

This review aims to summarize the clinical aspects of exacerbations in asthma and COPD from the perspective of the definition of exacerbations, epidemiology, and pathophysiology, with a special focus on the clinical significance of the presence of respiratory viruses.

Viral identification in early childhood wheezing illness may provide prognostic information regarding short- and long-term consequences. In the short term, RSV-induced bronchiolitis is associated with longer hospitalization than RV-induced bronchiolitis.20 The risk of reinfection with certain viruses varies; for example, there is a strong likelihood of RSV reinfection in the absence of ongoing passive immunity.21 Two studies found this risk to be as high as 74%22 and 76%23 if the initial infection occurred within the first year of life. Fourth, certain respiratory viruses have a well-documented association with subsequent asthma development and then exacerbation. More severe RSV illnesses in early childhood increase the risk of asthma development,24 and the risk for developing asthma is even greater after a RV wheezing episode in early life.25 Some children may have genetic risk factors for wheezing with RV26 or with RSV.

RV and EV infections also contribute to exacerbations of asthma, especially in children.11 Notably, many commonly used polymerase chain reaction (PCR)-based tests cannot distinguish RV from other EV (e.g., EV-D68).19 Viral sequencing analysis to specifically identify EV-D68 can be performed.27

Hand, foot, and mouth disease (HFMD) is an infectious disease that usually affects infants and young children under 5 years of age worldwide. HFMD typically causes self-limiting illness, but development of severe cardiopulmonary and neurologic complications have also been reported [1, 2]. The clinical manifestations are typically ulcerations in the oral cavity, buccal mucosa (enanthema) and tongue with peripherally distributed cutaneous lesions and vesicular rash (exanthema) on the palms of hands and soles of feet. Other parts of the limbs including knees, elbows and buttocks may also be affected. Transmission occurs via person-to-person through direct contact with respiratory secretion, saliva, fluid from blisters, and feces from infected individuals. A number of enteroviruses belonging to the family Picornaviridae cause HFMD, although human enterovirus 71 (EV71) and coxsackievirus (CV) type A16 are two of the most important enteroviruses implicated in many large-scale outbreaks in Asian-Pacific countries including Japan, Taiwan, Malaysia, Singapore, and China [2–4]. Additional enterovirus species including CV-A6, CV-A10 and CV-A4 also cause HFMD [5–9]. Clinical symptoms resulting from CV-A16 as well as other enteroviruses are usually relatively mild and indistinguishable with low incidence of severe complications. In contrast, serious complications such as encephalitis, myocarditis, and poliomyelitis-like illness were observed when EV71 were reported as the causative pathogen [10–12].

HFMD has been continuously present and remains a major cause of morbidity and mortality of young children particularly in Asia. Typically, HFMD exhibits cyclical pattern of outbreaks every two to three years. Factors underlying the prevalence of HFMD remain controversial. Data from countries with long history of HFMD outbreaks suggest that dissemination is associated with socio-economic status, population ethnicity, regional climate [14–16], and attendance in school or care centers of school-age children. The magnitude of HFMD outbreaks appears to fluctuate [3, 18, 19]. HFMD in tropical climate countries, such as Malaysia, Singapore and Thailand, typically showed years-round activity with no discrete epidemic periods although peaks during the rainy and winter seasons were also detected depending on season, year, and geographic regions [20, 21]. At present, no specific treatment for HFMD exists. Vaccines or antiviral drug against EV71 are currently being developed in Taiwan, China and Singapore but are not yet commercially available [22–24]. Prompted by geographically widespread outbreaks, careful monitoring of the spatial and temporal epidemiology is considered to be of great importance to control the spread of HFMD according to the different regional characteristics. As reported by the Bureau of Epidemiology, Ministry of Public Health of Thailand, HFMD has shown an upward trend in the last five to six years. In June 2012, the largest recorded outbreak of HFMD occurred throughout the country. This outbreak affected more than 39,000 individuals, including three deaths, over a period of four to five months with hot spots in Chiang Rai and Mae Hong Son provinces. In our previous study, we monitored HFMD activity in Thailand between 2008 and 2012. Our results revealed that the HFMD epidemic in 2012 was significantly different from previous ones in Thailand including the size of the epidemic and the viruses detected [26, 27]. During the 2012 epidemic, beside a high prevalence of EV71 and CV-A16, multiple EV types such as CV-A6 were also detected. Even though the standardized 5' untranslated region (5'UTR) pan-enterovirus PCR and viral capsid protein 1 (VP1) gene typing PCR assays were used, approximately one third of the suspected cases, mostly young children, were negative for enterovirus by these assays. These findings raised questions regarding the sensitivity of the current assay in identifying causative viruses other than EV71 and CV-A16 that may be present below the limit of detection by conventional PCR. In recent years, metagenomic has become an important strategy for virus discovery in human and animal diseases [28–30]. This technique, based on recognition of sequence similarities following non-specific nucleic acid amplification, circumvents some of the limitations of virus isolation, serology, and the amplification of only known conserved genomic regions. To evaluate circulating enterovirus and previously uncharacterized viruses associated with HFMD, we describe here the virus community (virome) in fecal samples negative by RT-PCR for EV71 and CV-A16/A6 obtained from 29 pediatric patients with HFMD during the outbreak in Thailand in 2012.

HSV-1 is an enveloped, linear double-stranded DNA virus which is highly prevalent in most part of the world. Approximately 50–90% of the world’s population is seropositive for this virus (Smith and Robinson, 2002; Fatahzadeh and Schwartz, 2007). Diseases caused by herpes simplex virus include cold sores, keratoconjunctivitis, genital herpes and encephalitis (Fatahzadeh and Schwartz, 2007; Burcea et al., 2015; Sauerbrei, 2016). Treatments currently directed against HSV infections are nucleoside analogs such as acyclovir, valacyclovir, penciclovir, and famciclovir that target viral DNA polymerase (Vadlapudi et al., 2013). However, extensive use of these drugs has led to clinical problems with the emergence of drug-resistant virus strains, particularly in immunocompromised patients (Jiang et al., 2016). The discovery of new drugs to treat HSV infection has become an important goal of drug development.

Rhubarb is the rhizomes of plants that belong to the genus Rheum in the family Polygonaceae. Chinese Rhubarb includes Rheum tanguticum (R. palmatum var. tanguticum), Rheum palmatum, Rheum officinale, etc. The rhubarb contains several main chemical compositions such as anthraquinones, anthrones, stilbenes, tannins, polysaccharides, etc. (Cao et al., 2017). These compositions show a wide range of pharmacological activities, including antioxidant, anti-tumor, anti-microbial and anti-inflammatory activities (Lai et al., 2015; Cao et al., 2017). Moreover, anthraquinones derivatives like aloe-emodin, rhein, emodin, and chrysophanol, reportedly demonstrated antiviral effects (Semple et al., 2001; Lin et al., 2008; Schwarz et al., 2011; Wang et al., 2018). However, as with most Chinese herbal medicines, the application of rhubarb is limited due to its poor bioavailability and hydrophobicity. Therefore, it is necessary to find new ways for the usage of rhubarb in order to make better use of it. The field of nanotechnology is an advanced approach in modern materials science. Nanoparticles might resolve the biopharmaceutical problems related to improving the uptake of poorly soluble drugs, reducing toxicity and increasing the drug bioavailability (Onoue et al., 2014; Marella and Tollamadugu, 2018). Moreover, it is well documented that the unique properties of nanoparticles, such as small particle size, large surface area to volume ratios, and tunable surface charge, make nanoparticles attractive tools for viral treatment (Singh et al., 2017). In recent years, several nanoparticles have been reported for the treatment of viral infections, among them silver nanoparticles have proven to be active against several types of viruses (Galdiero et al., 2011; Singh et al., 2017).

Given the importance of antiviral effect of rhubarb and advantages of nanoparticles, we designed some assays to investigate the activity of R. tanguticum nanoparticles against herpes simplex virus type I. We first conducted plaque reduction assays using HEp-2 cells to test the capacity of these nanoparticles to inactivate the HSV-1 virions and block the viral attachment and entry into cells, following the evaluation of inhibitory effect on viral replication using real-time quantitative PCR, Western blot, and immunofluorescence methods. Furthermore, the in vivo efficacies of these nanoparticles were investigated with a mouse model of HSV-1 encephalitis. The positive results offer a novel promising way for the usage of Chinese herbal medicine to control the HSV-1 infection.

Respiratory viruses are common pathogens in adults hospitalized with pneumonia and are more frequently detected than bacterial pathogens in certain groups of patients. Influenza virus is the most well-known respiratory viral pathogen, but others, including respiratory syncytial virus (RSV) and parainfluenza virus, are also common [2, 3]. Such viral pathogens are not easily distinguishable based on clinical findings alone. Therefore, it is suggested that reverse transcription-polymerase chain reaction (RT-PCR) assays should be performed in patients when a viral pathogen is suspected. Such testing for respiratory viruses can decrease the inappropriate use of antibiotics and other medical resources.

Viral pneumonia is also a major cause of patient deterioration in the intensive care unit (ICU). Respiratory viruses are well-known for their high prevalence in patients with community acquired pneumonia (CAP) who exhibit milder clinical presentations. Furthermore, their role as nosocomial pathogens in the more severely ill group of patients is being highlighted. However, only limited data exist regarding the prevalence of respiratory viruses among healthcare associated pneumonia (HCAP) and hospital-acquired pneumonia (HAP) patients. Additionally, considering the narrow range of antiviral agents against respiratory viruses and the potential harm of invasive respiratory sampling for RT-PCR in critically ill patients, it is crucial to reveal in which patients should the sampling be performed, and whether such detection leads to a change in the clinical management or outcome of patients.

In this study, we aimed to identify the presence of common respiratory viral pathogens in patients with severe pneumonia who were admitted to the ICU, including those with CAP, HCAP, and HAP. In addition, we aimed to analyze the risk factors and clinical impact of such detection.

Human adenoviruses (HAdVs) belong to the genus Mastadenovirus within the family Adenoviridae. Adenoviruses are non-enveloped, icosahedral, double-stranded DNA viruses with genomes of 26–45 kb. The viral capsid is composed of two types of capsomeres: the hexon and the penton (which consists of the penton base and the fiber). Antigens at the surface of the virion are mainly type-specific. Hexons are involved in neutralization, and fibers in neutralization and haemagglutination-inhibition. A recombinant that has a unique combination of these three regions (penton base; hexon loops; fiber knob) derived from previously recognized genotypes will be assign a new genotype (http://hadvwg.gmu.edu).

Traditionally, the only basis for recognizing a new type of HAdV is by serology, and on the basis of their biological properties, HAdVs have been classified into 7 species (Human mastadenovirus A to G, HAdV-A to HAdV-G), including 52 human HAdV types, which are formally recognized by the International Committee on Taxonomy of Viruses (ICTV). In addition, novel HAdV genotypes (HAdV-53 to HAdV-68) were recently identified based on their bioinformatics and genomic analysis of the complete viral genome sequences (http://hadvwg.gmu.edu). Novel HAdV strains may arise from mutations or recombination among the different types of HAdVs.

HAdV can cause a variety of clinical diseases such as acute respiratory disease, gastroenteritis, and keratoconjunctivitis, which vary depending on the cell tropism of the viruses. Among the HAdV-associated respiratory diseases, viruses in species HAdV-B (HAdV-3, 7, 11, 14, 16, 21, 50, 55), species HAdV-C (HAdV-1, 2, 5, 6), and species HAdV-E (HAdV-4) [10–14] are recognized as the main pathogens responsible for the respiratory tract infection.

As the capital city of China, Beijing covers an area of 16,800 km2 with a large population of more than 19.72 million (Chinese Statistics Bureau, 2011). In order to elucidate the spectrum of the viral aetiology of acute respiratory infections and provide basic data to guide local disease prevention and control measures, a sentinel surveillance project on the viral aetiology of acute respiratory infections was initiated and sponsored by the Beijing Municipal Health Bureau in 2011. Adenovirus is one of the most common causes of viral acute respiratory infections. In this study, our primary aim was to identify the types of HAdV causing respiratory illness in Beijing since 2011, to avoid the overuse of antibiotics and to improve the level of diagnosis and treatment of respiratory viral disease especially HAdV associated disease in hospitals, and to provide scientific basis for prevention and control of HAdV causing respiratory illness.

The lower respiratory tract infection (LRTI) is one of the most common infections in the world, leading to significant morbidity and mortality in children. Accurate and early etiologic diagnosis will help clinicians to initiate appropriate antimicrobial therapy. Although molecular techniques directly applied to respiratory tract specimens could detect multiple pathogens with high specificity and sensitivity, the choice of sample type and sampling method is critical for optimal diagnostic efficacy.

Currently, specimens for diagnostic purpose by PCR include oropharyngeal (OP) swabs, nasopharyngeal (NP) swabs, NP aspirates, OP suction and sputum. Although upper respiratory tract specimens are commonly used in children with respiratory viral and some bacterial infections, there is concern whether the results reflect the cause of lower respiratory tract infection. Lots of studies have compared the yields of these upper respiratory tract specimens, and by PCR to identify viral or bacterial infections by PCR, they have found that the sensitivity of aspirate (or suction) is greater than that of swabs [6–8]. Compared with specimen from upper airway, excellent diagnostic sensitivity is observed when sputum is available [4, 9–11]. However, for children, especially young patients who cannot expectorate, a sterile negative pressure suction catheter is applied to obtain OP suction. Young children and parents may find this relatively invasive and distressing procedure unacceptable, thus limiting its use in routine clinical practice [9, 12]. In addition, those oropharyngeal suction or sputa, presumably from, or contaminated by secretions from the upper respiratory tract [13, 14]. Therefore, it is important to assess the prevalence of pathogens in different types of specimens.

To the best of our knowledge, there have been no reports describing the adequacy of different types of specimen for the simultaneous detection of several viruses and atypical bacteria using multiplex-PCR. Therefore, we used multiplex-PCR to compare the detection of 9 types of viruses and 2 atypical bacteria in paired sputum and OPS samples from children with lower respiratory tract infection.

“Colds” and “flu” are terms that have been coined to describe a combination of common symptoms, supposedly brought about by the actions of specific viral infections of the upper respiratory tract. These symptoms may include such familiar discomforts as sneezing, stuffy nose, irritation of mucous membranes, excess mucus production, sinusitis, cough, sore throat, malaise and fever, as well as exacerbation of asthma and COPD (chronic obstructive pulmonary disease). In some cases symptoms may spread to include the lower respiratory tract and lungs, and result in bronchitis, bronchiolitis, or pneumonia. However the symptoms may not be a direct result of virus replication, which in many cases is minimal in airway tissues, but rather an indirect consequence of virus-induced inflammatory responses.

In respiratory infections, whether they start in the nasal passages or oropharynx, or other parts of the airway, the invading virus initially encounters epithelial tissues, composed largely of epithelial cells and occasional dendritic cells and macrophages, which accordingly respond by means of the various antimicrobial strategies that make up the innate immune system, including defense peptides (antimicrobial peptides) and the secretion of various pro-inflammatory cytokines and other mediators of inflammation. Other molecules such as kinins are released and are probably responsible for some of the early symptoms. Phagocytic cells and various types of inflammatory cell may then be attracted to the site of infection. In addition the redox balance of the cells may be adversely affected, either by the virus infection itself or as a consequence of the pro-inflammatory response.

Since most of the symptoms reflect this common non-specific host response to infecting agents, rather than to the direct cytolytic or cytopathic effects of a specific virus, then a more rational therapeutic approach would be the application of anti-inflammatory agents, especially if the intention of the therapy is to ameliorate symptoms. If a potential safe anti-inflammatory agent also contains multiple antiviral activities, then this would provide a bonus.

The limitations of conventional antiviral therapy and prevention were illustrated in 2002 with the sudden appearance of the SARS (severe acute respiratory syndrome) pandemic. The novel coronavirus responsible for the disease (SARS-CoV) was quickly isolated and its genome sequenced; however no adequate antiviral treatment was deemed to be available at that time.

Several herbal extracts have been shown recently to possess a combination of bioactivities that could be useful in the control of colds, flu, and bronchitis, and, in retrospect, some of these could have been useful for SARS patients. Among these herbal preparations Echinacea extracts have become very popular, although not all of them are necessarily beneficial, as will be discussed.

Human adenoviruses (HAdV) are common causes of community-acquired infections. In immunocompetent individuals, adenovirus infections often manifest as upper respiratory tract infections, pharyngoconjunctival fever, or diarrhoea. As in the case of other viral respiratory pathogens, community outbreaks of adenovirus infections may occur, especially with respiratory tract infections and keratoconjunctivitis. Such outbreaks may carry substantial morbidity and mortality, particularly in terms of severe respiratory tract involvement [1, 2]. In immunocompromised hosts, adenovirus infections may present as respiratory tract infection, hepatitis, enteritis, haemorrhagic cystitis, disseminated infections, and graft loss in organ transplant recipients. High risk individuals include patients with primary immunodeficiencies (especially severe combined immunodeficiency syndrome), allogenic haematopoietic stem cell transplant and solid organ transplant recipients. Disseminated disease in immunocompromised patients may carry a case-fatality ratio of more than 50%.

Currently there are seven species of HAdV (A to G) with over 50 serotypes. Certain species/serotypes are characteristically associated with organ-specific infections. For example, adenoviral keratoconjunctivitis is often associated with species D, while enteric infections are often caused by F40 and F41. Respiratory tract infections, one of the commonest manifestations of HAdV infections, is frequently due to species B and C. There are considerable geographical variations in the prevalence of various species and serotypes causing respiratory tract infections. In recent studies from China, Malaysia, Croatia, and the USA, for example, species C is often the commonest serotype involved in community-acquired respiratory tract infections, followed by species B; while the serotypes C1, C2, and B3 were most frequently detected [4–8]. Similarly, species C is one of the commonest species involved in infections among the immunocompromised patients. Understanding the epidemiology and prevalence of various HAdV species and serotype (ideally within one’s locality) is important in order to choose the most appropriate diagnostic modality which demonstrates good sensitivity and specificity towards the clinically important strains.

Conventional viral culture has largely been supplanted by nucleic acid amplification tests in the diagnosis of adenovirus infections. The detection of adenoviral DNA by nucleic acid amplification offers excellent sensitivity and shorter turnaround time than viral culture, and is also a powerful tool in the discovery of novel viruses. Nucleic acid amplification assays also allows easier determination of viral serotypes and quantification of viral load in clinical specimens. The determination of viral load is especially important for immunocompromised hosts who have a higher risk of developing severe and disseminated infections. It is now well established that high levels of HAdV DNAemia portends disseminated diseases and monitoring of viral load in peripheral blood and stool in susceptible hosts may have a role in early diagnosis and pre-emptive treatment of high risk individuals [10–14]. Viral load study is also useful in monitoring the response to antiviral therapy such as cidofovir. A number of studies have been published on the development of HAdV quantitative PCR (qPCR) protocols. We have previously developed a qPCR assay that can detect HAdV serotypes 11, 34, and 35 and shown that persistence of HAdV in the lower respiratory tract is common among immunocompromised hosts even without clinical adenoviral infections, and the viral load was correlated with low absolute lymphocyte counts. In recent years a commercial qPCR assay kit was available for specific detection of HAdV which facilitates the diagnosis and monitoring of HAdV infections in clinical laboratories. Adenovirus PCR is also included in a number of other commercial multiplex PCR systems for clinical diagnostics, and we have shown that some of the newer technologies such as the resequencing microarray could also be used for the diagnosis of gastroenteritis and conjunctivitis due to HAdV [18, 19].

In some of the PCR assays, the primers and probes were either species- or type-specific or there were base mismatches when compared with hexon gene sequences of some HAdV strains available in GenBank. Hence, we attempted to design a primer/probe set that can cover HAdV species A to G. We compared the performance of our in-house HAdV qPCR protocol with the commercial assay using archival clinical specimens and proficiency test samples.

Viral neonatal and paediatric infections are characterised by a great heterogeneity of clinical manifestations and are considered as major causes of neonatal and paediatric morbidity and mortality (1). Almost 50 years ago, Paediatric Virology was not considered an isolated discipline and was included in the Paediatric Infectious Diseases section of the scientific field of Paediatrics (2,3). However, during the past two decades, new advances in the field of Clinical Virology and Molecular Medicine have expanded the level of knowledge on the prevention, diagnosis and treatment of viral infections occurring in infancy and childhood (4,5). These developments and changes highlight the demand for undergraduate and postgraduate medical education in Paediatric Virology, which combines Paediatrics with Virology, Epidemiology, Molecular Medicine, Evidence-based Medicine, Clinical Governance, Quality Improvement, and Pharmacology and Immunology (5).

The 3rd Workshop on Paediatric Virology was entitled ‘Paediatric Virology: Interaction between basic science and clinical practice’. It was held on October 7th, 2017 in Athens, Greece, as an official session of the 22nd World Congress on Advances in Oncology and the 20th International Symposium on Molecular Medicine. Its aim was to bring together virologists and paediatric health professionals and encourage them to collaborate as an international network to promote paediatric health. Moreover, during the workshop, Nobelist laureate Professor Harald zur Hausen, Emeritus Professor of Virology at the University of Freiburg in Germany, who received the 2008 Nobel Prize in Physiology or Medicine for his discovery of human papilloma viruses (HPVs) causing cervical cancer and Professor Anne Greenough, Professor of Neonatology and Clinical Respiratory Physiology at King’s College London, UK and Vice President of Science and Research at the Royal College of Paediatrics and Child Health (RCPCH), were honoured by the Paediatric Virology Study Group (PVSG) for their indisputable academic, research and publishing contribution to Paediatric Virology.

The present review provides an overview on the wealth of new material from different areas of neonatal and paediatric viral infections presented and discussed during the workshop. Interestingly, 7 out of the 10 top key messages (Table I) of our meeting, as well as both statements of Nobelist laureate Professor Harald zur Hausen, on the occasion of this workshop (Table II), included recommendations on specific prevention strategies against viral infections. Along with the significant role of human breast milk and respiratory syncytial virus (RSV) prophylaxis, these issues included the necessity of the vaccination policy in relation to the migration crisis, prevention of hepatitis in newborns, recent advances on influenza vaccines, male vaccination against HPVs and the the preventative role of probiotics in the management of viral infections in children.

Fetuses and neonates are susceptible to a wide variety of viral infections most commonly involving the central nervous system (CNS) in greater frequency than adults (81). Infections of the CNS are a very common worldwide health problem in childhood with significant morbidity and mortality. In children, viruses are the most common cause of CNS infections, followed by bacteria, and less frequently by fungi and other causes. Advances in the prenatal and perinatal care together with technological advent of imaging modalities have enabled timely detection and detailed exploration of symptoms and signs in the neonatal population starting from the fetal life. Although imaging is practically unable to set the diagnosis of viral infection in the fetuses and neonates, moreover to reveal the pathogens, it has, however, the potential to accurately suggest this scenario, map the extent of involvement and direct the investigation and the consultation accordingly. Additionally, it may reveal complications from viral infections that may cause confusion and usually require special treatment (81).

Some imaging findings are highly suggestive of CNS viral infections in fetuses and neonates (82). Familiarity with the clinical course, the route of transmission and the imaging appearances usually proves helpful in reaching the correct diagnosis and in prompting timely treatment. In general, sequelae of an intrauterine infection reflect a combination of the pathogens and the stage of fetal development at which the exposure occurred (83). Congenital infections, occurring during the second and third trimester, may persist in the neonate affecting its general and neurologic status (83). However, as a rule of thumb, the later the diagnosis of congenital infections is made, the more difficult it is to identify the agent. Additionally, the imaging findings may become non-specific and less conspicuous as incomplete white matter myelination may interfere (83).

If maternal viral infection is suspected, combining prenatal ultrasound and fetal magnetic resonance imaging (MRI) may document the extent of tissue damage and therefore contribute to treatment and counselling (84). Neonatal head ultrasound, sometimes computed tomography (CT), but mainly MRI (Figs. 1 and 2) may reveal sequelae from congenital viral infections (i.e., microcephaly, dystrophic periventricular calcifications, brain atrophy), which may even suggest the causative virus, such as cytomegalovirus (CMV) (85). In previously healthy neonates with viral infection, the imaging investigation of CNS begins with head ultrasound and if further imaging investigation is required, MRI is the modality of choice, even in an emergency setting (86). Non-complicated meningitis is easier to be recognised clinically; however, since complications of meningitis, such as abscesses, infarcts, venous thrombosis, or extra-axial empyemas are difficult to diagnose clinically, imaging plays a crucial role (87).

Depending upon the involvement of etiological agent, the infectious respiratory diseases of small ruminants can be categorized as follows [9, 14]:bacterial: Pasteurellosis, Ovine progressive pneumonia, mycoplasmosis, enzootic pneumonia, and caseous lymphadenitis,viral: PPR, parainfluenza, caprine arthritis encephalitis virus, and bluetongue,fungal: fungal pneumonia,parasitic: nasal myiasis and verminous pneumonia,others: enzootic nasal tumors and ovine pulmonary adenomatosis (Jaagsiekte).

Manytimes due to environmental stress, immunosuppression, and deficient managemental practices, secondary invaders more severely affect the diseased individuals; moreover, mixed infections with multiple aetiology are also common phenomena [5, 8, 13, 15].

These conditions involve respiratory tract as primary target and lesions remain confined to either upper or lower respiratory tract [7, 16]. Thus, these diseases can be grouped as follows [5, 8, 14, 17].Diseases of upper respiratory tract, namely, nasal myiasis and enzootic nasal tumors, mainly remain confined to sinus, nostrils, and nasal cavity. Various tumors like nasal polyps (adenopapillomas), squamous cell carcinomas, adenocarcinomas, lymphosarcomas, and adenomas are common in upper respiratory tracts of sheep and goats. However, the incidence rate is very low and only sporadic cases are reported.Diseases of lower respiratory tract, namely, PPR, parainfluenza, Pasteurellosis, Ovine progressive pneumonia, mycoplasmosis, caprine arthritis encephalitis virus, caseous lymphadenitis, verminous pneumonia, and many others which involve lungs and lesions, are observed in alveoli and bronchioles.

Depending upon the severity of the diseases and physical status of the infected animals, high morbidity and mortality can be recorded in animals of all age groups. These diseases alone or in combination with other associated conditions may have acute or chronic onset and are a significant cause of losses to the sheep industry [3, 10]. Thus, the respiratory diseases can also be classified on the basis of onset and duration of disease as mentioned below [3, 9, 14, 18]:acute: bluetongue, PPR, Pasteurellosis, and parainfluenza,chronic: mycoplasmosis, verminous pneumonia, nasal myiasis, and enzootic nasal tumors,progressive: Ovine progressive pneumonia, caprine arthritis encephalitis virus, caseous lymphadenitis, and pulmonary adenomatosis.