Epidemiological and molecular analysis of human norovirus infections in Taiwan during 2011 and 2012

BACKGROUND: The human norovirus (NV) circulates worldwide and is a major cause of epidemics, which have increased in Taiwan since 2002. NV in acute gastroenteritis (AGE) and non-acute gastroenteritis (asymptomatic) patients, including children and adults, have not been previously examined in Taiwan; therefore, we examined the epidemiology and phylogeny of NV in AGE and asymptomatic patients of all ages. METHODS: 253 stool samples were collected from August 2011 to July 2012 (including 155 AGE and 98 asymptomatic samples in Taiwan) and analyzed using reverse transcription-polymerase chain reaction (RT-PCR) for NV. Primers targeting the RNA-polymerase gene were used for RT-PCR to allow DNA sequencing of Taiwan NV strains and phylogenetic analyses. RESULTS: NV was detected in 24 (9.5%) of 253 stool specimens using RT-PCR. NV was isolated from all age groups (1 to 86 y) and those NV-positive samples were major identified from inpatients (79.2%, 19/24). Statistical analysis showed that the NV infectious rate of AGE patients was statistically significant (P < 0.05) for age, season and water type, respectively. Phylogenetic analyses of the RdRp region sequence showed that 24 NV isolates belonged to Genogroup II Genotype 4 (GII.4). They were closely related to the epidemic strain in Taiwan in 2006, the GII.4-2006b pandemic strain in 2006, and the GII.4-New Orleans strain in 2010. CONCLUSION: This study is the first to examine NV in sporadic AGE and asymptomatic patients in Taiwan. Furthermore, epidemic strains of isolated GII.4 were predominant in Taiwan during 2011 and 2012.