Evidence of the etiological predominance of norovirus in gastroenteritis outbreaks--emerging new-variant and recombinant noroviruses in Hungary.

Between January 2001 and December 2003, stool specimens from 262 (45%) of 581 reported outbreaks of gastroenteritis were investigated for noroviruses in Hungary. Specimens collected from outbreaks of non-bacterial gastroenteritis were examined by reverse-transcription polymerase chain reaction and enzyme immunoassay. In 253 (97%) of 262 outbreaks, norovirus was detected and confirmed by sequencing in 211 (81%). Hospitals (35%), day care centers (30%), and elderly homes (27%) were the most common settings. Diversity and frequency of the genotypes changed over time but with predominance (95%) of genogroup (GG) II strains. Strains grouped into 11 genotypes including an epidemic spread of new-variant GGII4 (Lordsdale virus) and a recently emerged group of natural recombinant strains (GGIIb/Hilversum polymerase) with four capsid types (Hawaii, Mexico, Snow Mountain, and Lordsdale). Clusters of epidemics including food-borne outbreaks were detected. According to this study, noroviruses are the predominant etiological agents causing gastroenteritis outbreaks in Hungary.