WASHINGTON, July 9 (UPI) -- The deaths of three squirrel breeders in Germany between 2011 and 2013 are being blamed on a virus that apparently jumped from the animals to the men.
The new form of bornavirus, a type usually found in horses, sheep, birds and rodents, has the potential to spread but has not been shown to do so from human to human.
The three men died within two to four months of developing symptoms of encephalitis -- fever, chills, weakness, confusion and difficulty walking. The condition, characterized by swelling of the brain, is usually caused by a virus, however testing did not reveal what caused their brains to swell.
At least two of the three men were known to have been bit or scratched by variegated squirrels, an exotic breed native to southern Mexico and Central America, leading researchers to run genetic tests on one of the animals.
The European Center for Disease Prevention and Control advised people in February not to feed or get close to squirrels after the potential link was made while additional studies were conducted.
The presence of the virus in the three men was confirmed in a study published in the New England Journal of Medicine. Doctors have said, however, that the threat to other people remains low, as additional humans and animals have yet to be found with it, and researchers are still unsure exactly how each of the men contracted the disease.
"It's likely that bornavirus, commonly found in horses and sheep and capable of causing neurological symptoms, was present in the squirrels that scratched these men, causing the neurological and behavioral symptoms," Dr. Marc Siegel, a professor of medicine at NYU Langone Medical Center, told HealthDay. "It is possible that this virus could spread to squirrels here in the U.S. and occasionally to humans, but we wouldn't see sustained spread, as there is no evidence of spread from human to human."