AN OUTBREAK of West Nile virus in Dallas, Texas, has prompted
the county to declare a health emergency and launch aerial
insecticide spraying after 200 cases and 10 deaths were reported
this summer. But how much of a threat is the virus really - and
could a minor bout of the disease be the only way to protect
yourself? Anything that kills people, of course, is a concern.
What is most worrying about West Nile is that it appears to be
on the rise - and that may not just lead to more West Nile
cases. It also means its nastier cousins, such as dengue,
chikungunya and tick-borne encephalitis, could flourish. West
Nile virus normally infects birds, and is carried between them
by mosquitoes. In temperate regions, the number of infected
birds rises steadily after mosquitoes become active in spring.
By late summer, so many birds have been infected that the
mosquito species which bite both birds and people occasionally
carry the virus from a bird to a human. Only one person in five
infected develops (mostly flu-like) s