Venezuelan equine encephalitis

Venezuelan equine encephalitis virus is a mosquito-borne viral pathogen that causes Venezuelan equine encephalitis or encephalomyelitis (VEE). It can affect all equine species, such as horses, donkeys, and zebras. Equines may suddenly die or show progressive central nervous system disorders after infection.

It is contractible by humans and will usually experience flu-like symptoms when infected. People with a weak immune system can become seriously ill or die. It is transmitted primarily by mosquitoes that bite infected animals then spread it to other animals by biting them.

The speed of the spreading disease depends on the subtype of the VEE virus and the density of mosquito populations. Many subtypes are localized to certain regions and stay in that area. Subtypes are associated with the rodent-mosquito transmission cycle. These forms can cause illness in humans but not generally in equines.

Epizootic subtypes can spread rapidly through large populations and are highly pathogenic to equines and can also affect human health. Equines, as opposed to rodents, are the primary carriers of the disease. Equines that are infected develop a large quantity of virus in their circulatory system. Blood-feeding insects pick up the virus and transmit it to other animals and humans.

In 1969, when the U.S. Biological warfare program ended, VEE virus was one of seven standardized biological weapons it had developed.

In April, 2009, the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick reported that samples of Venezuelan Equine Encephalitis were discovered missing during an inventory of a group of samples left by a departed researcher. It was also reported that the samples were likely among those destroyed when a freezer malfunctioned.