“Decades after it stopped using the animal-borne virus that causes the disease Q fever as a biological weapon, the Pentagon is still trying to develop a vaccine to protect troops from the highly infectious disease,” USA Today reports.

“Called a class B bioterrorism agent by the Centers for Disease Control and Prevention, Q fever is carried mostly by sheep and goats and travels by air. U.S. troops fighting in Iraq returned home with the disease, military medical reports show.”