A mosquito sample collected by a Hebrew University researcher three decades ago in southern Israel has produced a previously unknown virus closely related to some of the world’s most dangerous mosquito-borne bacteria — yet incapable of infecting non-insect hosts.

This quality led some to dub it “the friendly virus.”

Friendlier still is the fact that the virus may help scientists better understand, and thus treat, similar but dangerously infectious viruses.

Known as Eilat, the virus was discovered in a mosquito sample taken by Joseph Peleg of The Hebrew University in the early 1980s. It was shipped from one laboratory to another for three decades, as part of a collection of over 5,000 other unidentified mosquito samples. Its uniqueness was only recently recognized, by Robert Tesh, the director of the World Reference Center for Emerging Viruses and Arboviruses, and his graduate student Farooq Nasar at the University of Texas.

“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 Nasar.

“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,” Nasar added.

The researchers expect Eilat could aid in the development of new vaccines and diagnostic measures against insect-borne diseases.

“All the researchers knew about Peleg’s specimen was that it killed insect cells while leaving animal cells untouched, a very unusual behavior,” said a report by the University of Texas Medical Branch, published in the Galveston Daily News on Tuesday. “So they sent it to a lab at Columbia University that specializes in doing highly intensive searches for the genetic material of viruses, a process called ‘deep sequencing.’ As it turned out, there were two new viruses in the sample. One virus killed insect cells, and the other — Eilat virus — infected them without doing any harm.”