The state of Virginia's top bug expert began setting traps in Fairfax and
Loudoun counties yesterday, searching for malaria-infected mosquitoes in
three places where a contractor said it discovered infected insects
recently, health officials said.
. . .
Health officials said they are no closer to finding the source of the
malaria that infected the two teenagers in the Sugarland Run neighborhood
of eastern Loudoun. Experts say there are at least three likely explanations.

First, a traveler could have been infected with malaria overseas and then
come to this area, where he or she could have been bitten by a mosquito
that then passed on the disease.

Second, immigrants or migrant workers who became infected in their native
countries could have carried the malaria parasite and passed it on to local
mosquitoes.

Third, a mosquito could have hitched a ride on a plane from an area where
malaria is endemic, then flown -- or been blown on the wind -- several
miles from Dulles International Airport to infect the teenagers.
. . .
Ronald Ward, a retired malaria expert at the Walter Reed Army Institute of
Research, speculated that "the mosquitoes picked up the malaria from
itinerant farm workers."

"As far as I know, no screening is done on migrant workers for various
infectious diseases," he said, "so that's something that should be checked
out."

Loudoun Health Director David Goodfriend said county officials have
approached employers in the Lansdowne area, where one of the pools of
mosquitoes tested by Clarke came up positive for malaria. Officials passed
out information in English and Spanish on malaria in the construction and
service industries, where many workers come from Latin American countries
where malaria is prevalent.