Molecular genotyping of Irish rotavirus strains.

Rotavirus is the primary etiological agent of gastroenteritis in infants and young children worldwide. In developing countries, it is estimated that rotavirus is responsible for one-third of all diarrhea-associated hospitalizations and 873,000 deaths annually. In industrialized countries, where mortality from rotavirus is low, infection is widespread, and nearly all children experience an episode of rotavirus diarrhea in the first 3-5 yr of life. Rotaviruses have important antigenic specificities including serogroup and serotype, and all viruses are classified accordingly. They are divided into seven morphologically indistinguishable but antigenically defined serogroups, delineated A through G. The human infecting rotaviruses include groups A, B, and C, and it is well documented that group A rotaviruses are the major causative agents of diarrheal diseases in children. They are responsible for 125 million cases of diarrhea annually. Within each serogroup, distinct serotypes exist. In group A rotavirus, serotype is specified by two viral proteins, VP4 and VP7. The neutralizing antibody response that is evoked by the antigenic determinants on VP4 and VP7 play an important role in protective immunity. The rotavirus genome consists of 11 double-stranded (ds) RNA segments, and each genomic segment encodes a different protein. A dual system of reporting rotavirus serotype exists because the VP4 and VP7 proteins are encoded by different genes and thus can segregate independently. The serotypes derived from VP7 are defined as G-serotypes. Currently 14 G-serotypes have been identified, and only 10 of these have been recovered from humans. The predominating G-types worldwide are G1, G2, G3, and G4, with G1 being the most prevalent type. Serotypes G5, G6, G8-G10, and G12 are rarely identified in humans and are usually recovered from animals. However, some of these unconventional types are now being frequently reported in humans, including G5, G8, and G9.