Epidemiology of Human Adenoviruses: A 20-Year Retrospective Observational Study in Hospitalized Patients in Bern, Switzerland

Akello, Joyce Odeke; Kamgang, Richard; Barbani, Maria Teresa; Suter-Riniker, Franziska; Leib, Stephen L; Ramette, Alban

The nucleotide sequences of the partial hypervariable hexon gene 1-7 from HAdV genotypes identified in this study were (Figures S1A and B ). Although HAdV infections are known to fluctuate over time, increased cases of HAdV infections were evidenced among young children every 4 years. This study is the first to report such recurring pattern. Previously, Heo and colleagues 23 showed that cases of HAdV respiratory infection are common during winter and spring. A study by Yao and colleagues concluded that HAdV prevalence may be related to age and season. 24 Our findings suggest that increased HAdV infection in Switzerland was related to age, but to a lesser extent to a particular season, as HAdV infections occurred throughout the year. Also when detected, HAdV was predominantly found among those aged ≤4 years. HAdV is therefore confirmed to be an important pathogen in clinical practice, mainly in the paediatric population. The high incidence of HAdV8 associated with ophthalmic infections among young adults, middle-aged and elderly in the years 2009 and 2010 is consistent with what was seen in Germany for instance. 25 Our finding is also consistent with other studies that showed HAdV8 to be a major culprit of adenovirus-associated conjunctivitis. 9, 26, 27 In addition, the predominance of HAdV species C genotypes, particularly HAdV1 and HAdV2, found among young children is also supported by other studies. 28 As young children have developing immune system, they may be more prone to infections. In the same line of evidence, most HAdV infections in immunocompromised hosts are known to be associated with HAdV species C genotypes 1 and 2. 14,29 Our study focused on molecular typing of HAdV positive samples collected between 1998 and 2017 among young children ≤4 years in order to identify the genotypes associated with an increase of cases of HAdV infection among this age category every 4 years. Various genotypes were identified to be causing HAdV infections, among which HAdV1 and HAdV2 genotypes were predominantly detected in the years with reoccurring peaks. These genotypes were also observed in the non-reoccurring peaks, but to a lesser extent. These typing results give insight into circulating HAdV genotypes causing disease mainly among young children who are known to be at high risk of HAdV infection.