WEST NILE virus, the Old World avian infection that invaded North America
last year and killed seven people in New York, is now on the march in Europe.
Since August it has killed some 20 horses in southern France in an area which
has not seen the infection since the 1960s. The prime suspects for bringing it
back are migrating birds.
The virus infects birds in Africa, west Asia and south-eastern Europe, and is
spread by mosquitoes. It can cause fatal brain inflammation in horses and
people. In 1998 it appeared in Italian horses and last year somehow reached
North America, with fatal consequences. Some fear that migrating birds will
spread the infection through the Americas
(快猫短视频, 8 July, p 4).
There are infected birds across more of the north-eastern US this year than
last, but nowhere else yet. Some virologists deny that migrating birds are a
threat.
In France, they are the prime suspect. The only previously known outbreak of
West Nile virus in the Camargue, a region of the Rhone delta, occurred in the
1960s. This was controlled by intensive spraying for mosquitoes. Herv茅
Zeller of the Pasteur Institute in Paris believes migratory birds have now
brought it back. Local veterinary officials say there are large numbers of
cattle egrets in the area this year, but 鈥渨e have no idea which birds are
responsible鈥�, says Zeller.
Advertisement