Circulation of a novel pattern of infections by enteric adenovirus serotype 41 among children below 5 years of age in Kolkata, India.

Human adenovirus of strains subgenus F (AdV F) are the most common strains detected in acute gastroenteritis cases in developing countries. Subgenus F is represented by AdV serotype 40 (AdV-40) and AdV-41. Most of the reports have described the predominance of AdV-41 in acute gastroenteritis cases. To gain insight into the epidemiology and genetic variation of AdV-41 strains, we analyzed 1,053 stool specimens from children with diarrhea. Among them, 42 (4.0%) and 56 (5.3%) were positive for enteric adenovirus 40/41 by enzyme-linked immunosorbent assay (ELISA) and PCR, respectively. For 1,305 asymptomatic children, 9 (0.7%) and 22 (1.7%) samples were positive for enteric adenovirus 40/40 by ELISA and PCR, respectively. The age distribution revealed a higher frequency (90%) in children <24 months of age. AdV F infection was observed at a low frequency throughout the year, with an increased incidence occurring during February and March. Sequence analysis of one to three hypervariable regions (HVRs) of the hexon genes of 16 representative AdV-41 strains in this study confirmed circulation of a unique strain with genomic type cluster 1 (GTC1)/GTC2. However, sequence analysis of the fiber genes of these strains confirmed 15 amino acid deletions from the 15th repeat motif of the shaft region. The existence of two GTCs reflects the accumulation of amino acid mutations in the HVR of the hexon gene. The novel AdV-41 strain might follow the same infection pattern as AdV-40. There is no significant variation in the sequences of hexon and fiber genes among strains from symptomatic and asymptomatic children. Our data confirm the circulation of an AdV-41 strain with a novel pattern in Kolkata, India, among children below 5 years of age.