Source
Public Health Laboratory Service Communicable Disease Surveillance Centre, Gastrointestinal Diseases Division, 61 Colindale Avenue, London NW9 5EQ, UK. blopman@phls.org.uk
Abstract
BACKGROUND:
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".
METHODS:
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.
RESULTS:
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.
CONCLUSION:
This surveillance data challenges the view that Noroviruses infections exclusively have wintertime seasonality.