After infection, equines may suddenly die or show progressive central nervous system disorders.

Healthy adults who become infected by the virus may experience flu-like symptoms, such as high fevers and headaches.

People with weakened immune systems and the young and the elderly can become severely ill or die from this disease.

The speed with which the disease spreads depends on the subtype of the VEE virus and the density of mosquito populations.

Although other animals, such as cattle, swine, and dogs, can become infected, they generally do not show signs of the disease or contribute to its spread.

[citation needed] The Mucambo virus (subtype III) appears to have evolved ~1807 AD (95% credible interval: 1559–1944).

[2] In Venezuela the Mucambo subtype was identified in 1975 by Jose Esparza and J. Sánchez using cultured mosquito cells.

[5] Outbreaks of VEE generally occur after periods of heavy precipitation that cause mosquito populations to thrive.

June 1993 saw a bigger outbreak in the Venezuelan state of Zulia, as 55 humans died as well as 66 equine deaths.

It has been shown the invasive mosquito species Aedes albopictus is a viable carrier of VEE virus.

The TC-83 strain was generated by passing the virus 83 times through a guinea pig heart cell culture; C-84 is a derivative of TC-83.

[12] In April 2009, the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick reported that samples of Venezuelan equine encephalitis virus were discovered missing during an inventory of a group of samples left by a departed researcher.