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, <= 7 years of age suffering from acute gastroenteritis in Pune, Nagpur, and Aurangabad cities. All the specimens were subjected to RTPCR, 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 <= 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 20052006 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. J. Med. Virol. 81:922-932,2009. (C) 2009 Wiley-Liss, Inc.