Epidemiological, clinical, and molecular features of norovirus infections in western India.

The study was conducted to investigate the molecular epidemiology of noroviruses (NoVs) from western India. A total of 830 fecal specimens were collected during July 2005-June 2007 from children, < or =7 years of age suffering from acute gastroenteritis in Pune, Nagpur, and Aurangabad cities. All the specimens were subjected to RT-PCR, sequencing and phylogenetic analysis for detection and characterization of Genogroup I (GI) and GII NoVs. NoV positivity varied between 6.3% and 12.6% in different cities with the predominance of GII (96.6%). NoV infections were very common in the patients < or =2 years of age. A majority (55%) of the patients suffered from severe disease, however, vomiting was not experienced in 35%. Coinfections with rotaviruses were found in 10% cases. Summer month seasonality supported NoV infections in western India. The phylogenetic analysis of partial RNA polymerase and VP1 (capsid) genes identified 2 GI (GI. 2 and GI.6) and 5 GII (GII.4, GII.6, GII.7, GII.8, and GII.14) genetic clusters with possible occurrence of "2007 new-variant" of GII.4. Six different combinations of RdRp and capsid genes (GII.b/GII.3, GII.b/GII.4, GII.d/GII.3, GII.b/GII.18, GII.1/GII.12 and GII.3/GII.13) were also identified. GII.4 (52%) prevailed in 2005-2006 while the predominance of probable recombinant NoV strains (58%) was noted in 2006-2007 with the contribution of GII.b/GII.3 at 79% level. GII.b/GII.18 type identified in 37% infections in 2005-2006 was completely replaced by GII.b/GII.3 type in 2006-2007. This is the first report that highlights the norovirus epidemiology and strain diversity demonstrating possible circulation of new variants in patients with acute gastroenteritis from western India.