Dr Ben Lopman from the UK Health Protection Agency and European colleagues analyzed data collected on gastroenteritis in 10 European countries.
The data were compiled based on the number of outbreaks per month during 2002.
The team compared the genetic sequences from the isolated viruses.
Dr Lopman's team also compared the isolated viruses with historic data and with a central database of viral sequences.
The team found that in England and Wales, Germany, and the Netherlands, there was a striking increase in norovirus outbreaks in 2002. This increase coincided with the detection and emergence of a new norovirus variant (of genogroup II4).
They established that detection of the new variant preceded an unusual spring and summer peak of outbreaks in Germany, the Netherlands, and Finland.
|There was a striking increase in norovirus outbreaks in 2002.|
Dr Lopman commented, "Our combined data from 10 European countries shows that the striking increase and unusual seasonal pattern of norovirus gastroenteritis in 2002 arose concurrently with the emergence of a new virus variant."
"Had these observations been made in 1 country they could be dismissed as aberrations in surveillance, the result of changes in ecological circumstances, or because of the local circulation of a new variant."
"However, the data collected within our network lend support to anecdotal reports of an increase of an important infection and have allowed us to present a feasible virological explanation for the effect on public health."