Norovirus illness is a global problem: emergence and spread of norovirus gii.4 variants, 2001-2007

Abstract

Background. Noroviruses (NoVs) are the most common cause of viral gastroenteritis. Their high incidence and importance in health care facilities result in a great impact on public health. Studies from around the world describing increasing prevalence have been difficult to compare because of differing nomenclatures for variants of the dominant genotype, GII.4. We studied the global patterns of GII.4 epidemiology in relation to its genetic diversity. Methods. Data from NoV outbreaks with dates of onset from January 2001 through March 2007 were collected from 15 institutions on 5 continents. Partial genome sequences (n = 775) were collected, allowing phylogenetic comparison of data from different countries. Results. The 15 institutions reported 3098 GII.4 outbreaks, 62% of all reported NoV outbreaks. Eight GII.4 variants were identified. Four had a global distribution-the 1996, 2002, 2004, and 2006b variants. The 2003Asia and 2006a variants caused epidemics, but they were geographically