Molecular characterization and phylogenetic trends of human adenovirus F in pediatric gastroenteritis cases in Kolkata, West Bengal, India during 2022-2024.

Human Adenovirus F (HAdV-F) is the second leading cause of acute gastroenteritis in children below 5 years of age, contributing to about 2–11% of diarrhoea related hospitalization around the world. In post RV vaccine surveillance study in Kolkata, West Bengal revealed 10.8% HAdV-F positivity in children in spite of reduction of rotaviral diarrhoea. Thus, the current study was conducted to unveil the genomic diversity of circulating HAdV-F strains in this region during 2022–2024 in children under 5 years of age. HAdV-F positive samples were further characterized by partial sequencing of hypervariable region (HVR) of hexon and shaft region of long fiber protein. The results were compared to the sequences in NCBI GenBank using BLAST software and further analyzed by sequence alignment and phylogenetic characterization using maximum likelihood method with 1000 bootstrap replicates. Analysis was performed on the aligned nucleotide as well as amino acid sequences for substitutions. The genetic diversity of the circulating type 41 HAdV-F was found to be greater than that of type 40. A mutant variant with a 15 amino acid deletion in the 15th repeat motif region of long fiber tail reported previously from the region was found to be predominant. Children aged 6–12 months were most susceptible to HAdV-F infection. An increase in infection rate was observed with increase in average monthly temperature, humidity and precipitation. The present study highlights enteric adenoviruses as a second most important acute gastroenteritis in children after rotavirus. Genetic characterization of circulating HAdV-F strains fills up the lacunae in data on HAdV-F40/41 from Indian subcontinent.