A mosquito sample collected three decades ago in Israel's Negev Desert has yielded an unexpected discovery: a previously unknown virus that's closely related to some of the world's most dangerous mosquito-borne pathogens but, curiously, incapable of infecting non-insect hosts.

Researchers believe this attribute could make the Eilat virus a uniquely useful tool for studying other alphaviruses, a genus of largely mosquito-borne pathogens that includes the viruses responsible for chikungunya, Venezuelan equine encephalitis, western equine encephalitis and eastern equine encephalitis. In addition, the researchers say, Eilat could also aid in the development of new alphavirus vaccines, therapies and diagnostic techniques.

"This virus is unique it's related to all of these mosquito-borne viruses that cause disease and cycle between mosquitoes and animals, and yet it is incapable of infecting vertebrate cells," said University of Texas Medical Branch at Galveston graduate student Farooq Nasar, lead author of a paper on the virus now online in the Proceedings of the National Academy of Sciences. "It's a gift, really, because we can compare it to other alphaviruses and figure out the basis of their ability to infect a variety of animals, including humans."