Most horse owners are familiar with Eastern and Western equine encephalomyelitis, if only through the statement they receive from their veterinarian following their horses’ annual vaccinations. But there’s another “EE” that, while long absent from the United States, should not be forgotten: Venezuelan equine encephalomyelitis, or VEE.

The zoonotic disease recently made headlines when the Army announced it was investigating the whereabouts of three vials containing samples of VEE. Caree Vander Linden, a spokeswoman for the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick, Md., told the Associated Press that the vials were discovered missing last year during an inventory of a group of samples left by a departing researcher. According to reports, investigators are trying to determine if these samples were among those destroyed when a freezer malfunctioned.

VEE is a non-contagious viral infection of horses and other equids that can cause a severe and typically fatal encephalitis/encephalomyelitis, which is defined as an inflammation of the brain and spinal cord