Great diversity of group A rotavirus strains and high prevalence of mixed rotavirus infections in India

We previously observed a marked diversity of rotavirus strains and a high p revalence of the uncommon serotype G9 in a small survey of rotavirus strain s collected from six centers in India. In the present study, we characteriz ed a larger collection of strains from children hospitalized with severe di arrhea in seven Indian cities between 1996 and 1998. A total of 287 strains were G and P genotyped by reverse transcription-PCR, and some were further characterized by electropherotyping and subgrouping. Of the four strains c ommon globally, three were found in only 43% of samples (P[8], G1, 15%; P[4 ], G2, 22%; P[8], G4, 6%), whereas G9 strains made up 17% of the total. Thr ee different G9 strains were present: a P[8], G9 strain, which displayed th e long electropherotype and subgroup II VP6 specificity, and two P[6], G9 s trains, one with the long electropherotype and subgroup H specificity and t he other with the short electropherotype and subgroup I specificity. Marked diversity was observed among strains collected from different cities and c ollected over time. Of the 253 strains that were fully typed, 54 (21%) had a mixed G or P genotype. Serotype G2 strains were detected more often in in fections caused by single strains than in mixed infections (P < 0.05), wher eas serotype GI strains were found more often in mixed infections than in i nfections caused by single strains (P < 0.05). The diversity of rotavirus s trains and the high prevalence of mixed infections confirm trends reported earlier and help to better characterize the strains of rotavirus circulatin g in India. Vaccines under development should clearly target G9 strains, an d G9 should be included as one of the common global serotypes.