Evolution of norovirus.

Norovirus (NoV) is now the dominant aetiological agent of acute gastroenteritis, and, with the recent introduction of rotavirus vaccines in many countries, this is likely to remain the case. NoV has a significant impact on human wellbeing in terms of morbidity, economic costs and mortality in developing countries. NoVs are divided into six genogroups (GI-GVI), but only GI, GII and GIV are known to infect humans, with GII being the most prevalent, causing >95% of human infections. The immune system is thought to drive selection of emerging pandemic NoVs through both antigenic drift and shift. This phenomenon results in the replacement of dominant circulating viruses approximately every 3 years, with new variants able to re-infect hosts previously infected with earlier viruses. This review explores the evolutionary aspects of contemporary NoVs.