Rotaviruses: is their surveillance needed?

Rotaviruses, a major cause of gastroenteritis in children worldwide accounts for around 0.5 million deaths annually. Owing to their segmented genome and frequently evolving capability, these display a wide variation in their genotypes. In addition to commonly circulating genotypes (G1, G2, G3, G4, G9, P[4] and P[8]), a number of infrequent genotypes are being continuously reported to infect humans. These viral strains exhibit variation from one geographical setting to another in their distribution. Though the introduction of vaccines (RotaTeq and Rotarix) proved to be very effective in declining rotavirus associated morbidity and mortality, the number of infections remained same. Unusual genotypes significantly contribute to the rotavirus associated diarrhoeal burden, may reduce the efficacy of the vaccines in use and hence vaccinated individuals may not be benefited. Vaccine introduction may bring about a notable impact on the distribution and prevalence of these viruses due to selection pressure. Moreover, there is a sudden emergence of G2 and G3 in Brazil and United States, respectively, during the years 2006-2008 post-vaccination introduction; G9 and G12 became predominant during the years 1986 through 1998 before the vaccine introduction and now are commonly prevalent strains; and disparity in the predominance of strains after introduction of vaccines and their natural fluctuations poses a vital question on the impact of vaccines on rotavirus strain circulation. This interplay between vaccines and rotavirus strains is yet to be explored, but it certainly enforces the need to continuously monitor these changes in strains prevalence in a particular region. Furthermore, these fluctuations should be considered while administration or development of a vaccine, if rotavirus associated mortality is ever to be controlled.