International Surveillance System Suggests 2002 Gastroenteritis Outbreaks Were Likely a Result of a New Variant of Norovirus

Newswise -- The increase in severe outbreaks of gastroenteritis in 2002, including the notorious outbreaks on U.S. cruise ships -- were probably a result of a new variant of norovirus, conclude authors of a study in this week's issue of The Lancet.

Ben Lopman from the UK Health Protection Agency and European colleagues analyzed data collected through a collaborative research and surveillance network of viral gastroenteritis in 10 European countries. Data were compiled based on the number of outbreaks per month during 2002, and genetic sequences from the isolated viruses were compared. Comparisons were also made with historic data from a retrospective review of surveillance systems and with a central database of viral sequences.

In England, Germany, and the Netherlands, there was a striking increase in norovirus outbreaks in 2002 that coincided with the detection and emergence of a new norovirus variant (of genogroup II4), which had a consistent mutation in the polymerase gene. Detection of the new variant preceded an unusual spring and summer peak of outbreaks in three countries (Germany, Netherlands, and Finland).

Lopman comments, "Our combined data from ten 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 one 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."

Source: The Lancet.