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Biological Warfare (cont.)


The monkeypox virus, which is found in Africa, is a naturally occurring relative of variola. The first case of human monkeypox was identified in 1970, but fewer than 400 cases have been diagnosed since. Some concern exists that monkeypox may be weaponized, however, human monkeypox is not as potent as smallpox. Pneumonia due to monkeypox may cause death in about half of people who develop it.

Arboviral Encephalitides

The arboviral encephalitides with high fatality rates include Venezuelan equine encephalitis (VEE) virus, western equine encephalitis (WEE) virus, and eastern equine encephalitis (EEE) virus. They are members of the Alphavirus genus and are regularly associated with encephalitis. These viruses were recovered from horses during the 1930s. VEE was isolated in the Guajira peninsula of Venezuela in 1930, WEE in the San Joaquin Valley of California in 1930, and EEE in Virginia and New Jersey in 1933. A more common, but milder arboviral disease, is West Nile, which is caused by a flavivirus.

Although natural infections with these viruses occur following bites from mosquitoes, the viruses are also highly infectious when spread through the air. If intentionally released as a small particle aerosol, this virus may be expected to infect a high percentage of people exposed within a few miles.

VEE virus has the capacity to produce epidemics. Outcomes are significantly worse for the very young and the very old. Up to 35% of people infected may die. WEE and EEE typically produce less severe and widespread disease but are associated with death rates as high as 50%-75% in those with severe illness.

Signs and Symptoms

  • VEE: After an incubation period of two to six days, people with VEE develop fevers, chills, headache, aches, sore throat, and sensitivity to light (eyes). They may become mildly confused, have seizures or paralysis, or go into a coma. For those who survive, their nervous system functions usually recover completely.
  • EEE: The incubation period for EEE varies from five to 15 days. Adults may have certain early symptoms up to 11 days before the onset of nervous system problems such as mild confusion, seizures, and paralysis. Signs and symptoms include fever, chills, vomiting, muscle rigidity, lethargy, slight paralysis, excess salivation, and difficulty breathing. Children frequently develop swelling on their face and near their eyes. A significant percentage of survivors of severe disease have permanent nervous system problems such as seizures and various degrees of confusion (dementia).
  • WEE: The incubation period is five to 10 days. Most people have no symptoms, or they might develop a fever. Other symptoms include nausea, vomiting, headache, a stiff neck, and drowsiness. Up to a majority of victims younger than 1 year of age have seizures. Typically, adults recover completely. Children, especially newborns, may have lasting nervous system problems.


Laboratory tests, including nasal swab samples, may show any of the three viruses.


No specific treatment is available. Doctors will help control symptoms. For some people, that may include medications to control fever and seizures or help breathing.


There are no commercially available vaccines against any of the arboviral encephalitides. They are experimental and only available for researchers who work with the virus.

Medically Reviewed by a Doctor on 11/20/2017

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