St. Louis encephalitis (SLEV) is a virus from the same family as the West Nile virus. Both of these viruses are transmitted by mosquitoes which have been infected by birds. St. Louis encephalitis can cause damage to the central nervous system.
St. Louis encephalitis is caused by something called an arbovirus, which is short for "arthropod-borne virus". Arboviruses are spread by some invertebrates, or arthropods. Blood-sucking insects such as mosquitoes are the most frequent of these arthropods.
The St. Louis encephalitis virus can be found in the Caribbean, Canada, Central America, South America and the United States. Its prolific time of year is during the late summer and fall.
Mosquitoes that are carrying SLEV like to habituate areas of polluted waste water. Other favorite locations are swimming pools, irrigated farms, pastures and swamps. Mosquitoes are drawn to any place that has standing water.
Upon infection, the virus will not be noticeable for anywhere between four and 21 days. At that point, the central nervous system will begin to be affected.
Most people who become infected have a mild case of infection or they may not show any symptoms at all. Mild symptoms may include fever, headache, dizziness and fatigue.
In somewhat more serious cases, other symptoms can include muscle pain, tremors, vomiting and diarrhea, confusion and delirium. The most severe cases can end in convulsions and death.
Any treatment of SLEV can only be aimed at controlling and reducing the severity of symptoms.
In most cases, the infection will improve in a matter of days, though complications will sometimes arise. These may include other infections, blood clots, internal bleeding and pneumonia.
Those at highest risk for serious symptoms St. Louis encephalitis are infants, elderly people and those with HIV. Those infected in this high risk category who recover may have a very slow recovery, that may take many months. The death rate in this category can be from five to 30 percent.