Asian mosquitoes carry dangerous virus.

The Asian tiger mosquito, Aedes albopictus, hitched a ride to the United States in 1985. Since that time, federal scientists have been anxiously monitoring these biting insects, which in Asia are known to carry several microbes that cause human illness.

In 1990, entomologists reported they had isolated the so-called Potosi virus from specimens of Asian tiger mosquitoes collected in Potosi, Mo. (SN: 11/17/90, p.309). The Potosi virus is not known to cause illness in humans.

Now, U.S. scientists have reason to worry. Carl J. Mitchell of the Centers for Disease Control's division of vector-borne infectious diseases in Fort Collins, Colo., and his colleagues describe finding a disease-causing virus in Asian tiger mosquitoes collected from a tire dump in Polk County, Fla. This dump, which has since been destroyed, contained about 3 million tires when the mosquitoes were collected.

In the July 24 SCIENCE, Mitchell's team describes isolating 14 strains of eastern equine encephalitis (EEE) from tiger mosquitoes collected at the dump. EEE, which affects both horses and humans, can cause fever, chills, nausea, and a potentially lethal inflammation of the brain.

The report adds to earlier fears that the Asian tiger mosquito could fuel outbreaks of virus-caused human disease in the United States. The insect, which has spread rapidly through the Southeast and Midwest, "is a very aggressive biter," Mitchell says. He adds, however, that "we don't have any evidence that A. albopictus is transmitting this virus to humans."

Entomologists don't know whether the mosquitoes found in the Florida tire dump are unusual or indicative of a more widespread problem. The Centers for Disease Control has asked five state vector-control agencies to collect Asian tiger mosquitoes from their freshwater swamp breeding habitats. "If we find that it is becoming frequently infected, then we definitely would have reason for concern," Mitchell says.