Human adenovirus infection in infants under one year of age is associated with increased mortality in Malaysia

Aims: This study aimed to characterize the genetic diversity of human adenovirus (HAdV) strains isolated from paediatric patients hospitalized with respiratory distress in Seremban, Malaysia, between 2013 and 2017, and to assess their association with paediatric mortality.Methodology and results: A total of 352 retrospective specimens were collected from patients presenting with respiratory distress at the Paediatric Department of Hospital Tuanku Jaafar, Seremban, from 2013 to 2017.Virus isolation was performed using A549 cell cultures, followed by PCR amplification, Sanger sequencing, and phylogenetic analysis.Serotypes and genetic relatedness were determined based on sequences of the hexon, penton, DNA polymerase, fiber, and virus-associated RNAII genes, and compared with reference sequences from GenBank.Among the 352 specimens, 349 tested positive for HAdV, 1 for influenza A virus (INFA), 2 for influenza B virus (INFB), 1 for parainfluenza virus type 1 (PIV1), 3 for parainfluenza virus type 3 (PIV3), and 25 for respiratory syncytial virus (RSV).Co-infections were detected in 23 patients with HAdV and RSV, 3 with HAdV and PIV3, and 1 each with HAdV-INFA and INFB-PIV1.Of the HAdV-positive samples, 26 isolates were successfully cultured.Phylogenetic analysis identified 22 isolates (84.6%) as HAdV serotype 7, 3 isolates (11.5%) as serotype 3, and 1 isolate (3.9%) as subgroup D. HAdV species B was the most prevalent group circulating during the study period.The mortality rate associated with HAdV infection was significantly higher among patients under one year of age compared to older children.However, no significant association was observed between gender, HAdV serotype, and clinical outcome.Conclusion, significance and impact of study: HAdV species B, particularly serotype 7, was the predominant adenovirus group circulating in Seremban, Malaysia, between 2013 and 2017.Although younger patients (below one year) showed higher mortality rates, neither serotype nor gender correlated significantly with clinical outcome.These findings underscore the importance of continuous HAdV surveillance and its relevance to paediatric respiratory health management in Malaysia.