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.