Background: Human adenoviruses (HAdVs) can cause a variety of human illnesses, with associated temporal and geographic changes in disease incidence. We report the emergence of an outbreak of HAdV infections in Singapore, presumably caused by a change of the predominating type to HAdV-7. We examined the clinical features of children admitted with HAdV infection to 1 institution and the risk factors for severe infection.Materials and Methods: This is a retrospective case-control study of all HAdV-infected children admitted during weeks 1 to 19 in 2013, as identified from laboratory records. A descriptive retrospective analysis of epidemiology, clinical data and the outcome of these children was also performed. Patients with severe infections were defined as cases, those with non-severe infections as controls, and the 2 groups were compared to find possible independent risk factors. Results: : Eighty-five patients with HAdV infection were studied, including 11 (12.9%) cases and 74 (87.1%) controls. Binary logistic regression showed that cases were more likely to be <2 years old (adjusted OR 10.6, 95% CI, 1.8 to 63.2) and to have significant comorbidities (adjusted OR 19.9, 95% CI, 3.4 to 116.1) compared to controls. The predominant type in 2013 was HAdV-7, which differed from 2011 and 2012, when HAdV-3 was more common. There was a trend towards pneumonia being more common in patients infected with HAdV-7 than in patients infected with other types, although this did not reach statistical significance (OR 2.8, 95% CI, 0.9 to 8.7). Conclusion: The emergence of HAdV-7 in a population where other HAdV types had circulated previously may have caused the outbreak in Singapore, and this was associated with more serious infections in children. Young age (<2 years) and significant comorbidities were associated with more severe HAdV infection.
Human adenoviruses (HAdVs) are well known pathogens that cause a variety of human illnesses. They are non-enveloped, linear double-stranded deoxyribonucleic acid (DNA) viruses. More than 50 distinct serotypes have been identified since the early 1950s. The wide spectrum of symptoms includes upper respiratory tract illness, pneumonia, conjunctivitis, cystitis and gastroenteritis. Characteristic illnesses associated with HAdVs are pharyngoconjunctival fever, epidemic keratoconjunctivitis and acute respiratory illnesses in military recruits. Immunocompromised persons are known to be affected by more severe disease. The virus spreads rapidly in crowded environments, typically causing epidemics in military recruits and hospitalised or institutionalised civilians. In the paediatric population, particularly in children with underlying respiratory disease, the illness can be severe and life-threatening. Due to a large proportion of infections being subclinical and due to a lack of surveillance for HAdV infections in many countries, most community outbreaks remain unreported. A community outbreak of adenovirus was reported in Taiwan in 2011, using a vigilant surveillance system comprising 12 contract virological laboratories across the country.
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