Noroviruses are the most common cause of gastroenteritis outbreaks in industrialised countries. Gastroenteritis caused by Norovirus infection has been described as a highly seasonal syndrome, often referred to as "winter vomiting disease".
The Public Health Laboratory Service Communicable Disease Surveillance Centre has systematically collected reports of laboratory confirmed cases of Norovirus-gastroenteritis since 1995. We analysed these data for annual and seasonal trends and age distribution.
A mid-summer peak in reported cases of Norovirus was observed in 2002, unlike all six previous years when there was a marked summer decline. Total reports from 2002 have also been higher than all previous years. From the first 10 months of 2002, a total of 3029 Norovirus diagnoses were reported compared the previous peak in 1996 of 2437 diagnoses for the whole 12-month period. The increase in 2002 was most marked in the 65 and older age group.
This surveillance data challenges the view that Noroviruses infections exclusively have wintertime seasonality.
Lopman BA, Reacher M, Gallimore C, Adak GK, Gray JJ, Brown DW. (2003). A summertime peak of "winter vomiting disease": surveillance of noroviruses in England and Wales, 1995 to 2002. BMC Public Health, (3)