Human adenoviruses (HAdV), classified into seven species, A-G, are 90–100 nm diameter, nonenveloped viruses with an icosahedral nucleocapsid containing a double stranded DNA genome. Although HAdV infections are usually self-limited and mild adenoviruses can sometimes cause colds, gastroenteritis, acute respiratory infections, conjunctivitis, haemorrhagic cystitis, and meningoencephalitis.
Only limited information is available on their epidemiology in some jurisdictions. Furthermore, species classification of HAdV positive samples is not routinely performed in clinical diagnostics laboratories.
Alban Ramette of University of Bern, Switzerland, led a retrospective observational study from laboratory confirmed HAdV cases collected between 1998 and 2017 in Bern HAdV clinical biobank, at the Institute for Infectious Disease (IFIK), following referral of specimens by clinicians. The results were published in the journal Clinical Epidemiology.
Roughly 4% (1,302) of samples sent for screening were positive for adenovirus. The majority (57%) of positive samples were from patients aged 0-4 years old. Upper respiratory tract samples were most commonly (56%) positive, followed by conjunctivitis (19%), then stool (14%). Upper respiratory tract and stool samples were most commonly positive among young children. Conjunctivitis was most common in adults.
Ophthalmic infection was associated with HAdV8, respiratory tract infection with species C (HAdV1, HAdV2, and HAdV5) and B (HAdV3). HAdV2, HAdV3 and HAdV41 were identified in gastrointestinal infection. HAdV2 and HAdV3 were associated with more than one clinical presentation. HAdV1, HAdV2, HAdV3, and HAdV41 were most common in young children.
The results should be interpreted with caution as the presence of HAdV in respiratory tract and stool samples could be detected incidentally, however the majority of disease samples analyzed in the study were suspected to be due to adenovirus infections by a diagnosing physician. This suggests that the numbers of adenovirus infections found in the study may be an underestimation. Some samples could not be genotyped, which may have impacted the results.
“The findings support that variation in the clinical presentation and epidemiology of HAdV genotypes exists, and may present unexpected patterns when long-term records are examined. By uncovering HAdV molecular epidemiology and its clinical presentations in our 20-year observation study, we have highlighted the existence of differences in HAdV infections among various age categories and circulating HAdV genotypes,” concluded the authors.