The monkeypox virus is a naturally occurring relative of variola, which is found in Africa. 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.
The viral encephalitides, Venezuelan equine encephalitis (VEE) virus, western equine encephalitis (WEE) virus, and eastern equine encephalitis (EEE) virus, 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.
Although natural infections with these viruses occur following bites from mosquitos, 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 2-6 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 5-15 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. Up to 30% of survivors of severe disease have permanent nervous system problems such as seizures and various degrees of confusion (dementia).
- WEE: The incubation period is 5-10 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 90% of victims younger than 1 year 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 3 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.
A vaccine for VEE can be given as an injection for those at high risk, such as laboratory field personnel. About 20% of those who receive the vaccine fail to respond to it, meaning they would not be protected by the vaccine. An additional 25% of those vaccinated develop high fever, chills, and feel sick enough to be in bed.
A different vaccine was developed for those who did not develop protection from the initial activated vaccine. It is an inactivated vaccine, which produces only mild tenderness at the injection site. Shots are given at 2- and 4-week intervals until the person responds and develops antibodies as protection.
The EEE vaccine is inactivated and given as an injection (1 to start and another 28 days later). There are no serious side effects or long-term problems with this vaccine. Boosters are required.