Molecular epidemiology of human G2P[4] rotaviruses in Taiwan, 2004-2011.

In 2006, two rotavirus vaccines (Rotarix and RotaTeq) became available on the private market in Taiwan. Although vaccine coverage is currently low, molecular surveillance of rotavirus strains can provide pertinent information for evaluation of the potential impact of vaccine introduction and infection control. During January 2008-December 2011, children aged <5 years hospitalized with acute gastroenteritis were enrolled from sentinel surveillance hospitals in three geographic areas of Taiwan. Fecal specimens collected from enrolled patients were tested for rotavirus by enzyme immunoassay and reverse transcriptase-polymerase chain reaction. For genotyping, gene specific primer sets were used to amplify and sequence the genes encoding the neutralization antigens, VP7 and VP4. The resulting sequences were then subjected to phylogenetic analysis. In brief, a total of 4,052 fecal specimens were tested and 742 (18%) samples were positive for rotavirus. The annual range of rotavirus positive specimens varied between 16% and 20.7%. Of all specimens, genotype G1P[8] (63.3%) was the predominant strain, followed by G2P[4] (12.5%), G3P[8] (11.7%), and G9P[8] (5.1%). Uncommon strains were also detected in low percentages. We observed that the rotavirus positivity rate steadily decreased from 21% to 16% during 2008-2010, then slightly increased to 20% in 2011, when an increase in the number of G2P[4] cases was observed. Sequence and phylogenetic analysis was carried out to help understand any potential changes of G2P[4] rotaviruses over time. A number of G2P[4] strains collected between 2004 and 2011 were analyzed in detail and our analyses showed marked genetic and antigenic variability in the VP7 and VP4 genes. The Taiwanese strains could be classified into two major G2 VP7 lineages (IV and V) and two major P[4] VP4 lineages (IV and V) and several minor sublineages within lineage IV. Lineage V within both G2 and P[4] represented newly recognized genetic variants of the respective genotypes. The distribution of individual combinations of the G2 and P[4] (sub)lineages showed some temporal variations. This study provides further evidence for the great genetic diversity among G2P[4] strains and helps understand the epidemiological trends of these strains among children in Taiwan.