| Summary: | St. Louis encephalitis (SLE), named for the city where the first cases were recognized in 1933, is the most common variety of viral encephalitis in the USA. Most people who are infected with the virus never show any outward symptoms. Those who do exhibit symptoms face a very serious threat to life. The symptoms of SLE are generally flu-like, with fever, headaches and lethargy. Severe cases of SLE can cause seizures, double-vision, paralysis and death. The elderly and the young are most at risk from SLE. As many as 30% of elderly patients infected with SLE die. The agent that causes St. Louis encephalitis is a virus, thus antibiotic treatments are not effective. There is no vaccine for the virus and (like all viruses) there is no cure. | ||||||||||
| Contact a Health Care Professional Immediately: | Elderly and children who exhibit flu-like symptoms during a known outbreak of encephalitis should contact their Health Care Provider immediately. | ||||||||||
| Source of Infection/Mode of Transmission: | The virus that causes St. Louis encephalitis in humans is thought to occur naturally in birds. It is transmitted among birds and between birds and other animals by blood-feeding mosquitoes. The SLE virus is not known to cause disease in birds and once infected
individual birds are immune to further infection. Significant quantities of the virus are evident in birds 1-2 days following infection with viral levels falling rapidly 1-3 days later.
The virus is transmitted to man and other hosts by short-lived mosquitoes of the genus Culex. These mosquitoes are very common in the USA. Humans (and most other mammals) are very poor carriers of SLE. |
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| Symptoms: | Most people who are infected with St. Louis encephalitis never show any symptoms. Mild cases may occur with flu-like symptoms, a slight fever and headache. Severe infections are marked by a rapid onset, headache, high fever, disorientation, coma, tremors, convulsions, paralysis or death. | ||||||||||
| Diagnosis: | Diagnosis of SLE requires a blood test and/or spinal tap. | ||||||||||
| Treatment: | Your physician will probably attempt to treat the symptoms of SLE because there is no cure. Individuals experiencing flu-like symptoms in areas of known encephalitis should see their physician. | ||||||||||
| Geographic/Seasonal Distribution: | |||||||||||
| Protections: | Your best protection from St. Louis encephalitis is to avoid situations which put you at risk from mosquito bites, especially in areas and at times when mosquitoes are active. Culex mosquitoes are most active from about one hour before sundown, through the night and until one hour after sunrise. They breed in fresh-water and are most prevalent following a rain. If you must go out in these conditions you should wear protective clothing such as long pants and long sleeve shirts. Insect repellants containing the chemical DEET are reported to be effective in protecting against mosquitoes of the genus Culex. Adults should wear a concentration of DEET less than 30 percent while children should wear a concentration of 10 percent or less. There are some recent reports that DEET may pose a danger in usage. As always, consult with your physician before using any medication or treatment. | ||||||||||
| Notes: | In areas where SLE occurs, the local health authorities have established a "Sentinel" program, where caged birds, usually chickens, are monitored for the presence of SLE antibodies. It is important to realize that this monitoring program detects the presence of SLE
only after the disease cycle is underway.
The SLE virus is an arbovirus (a virus transmitted via arthropods) classified in the family Togaviridae and genus Flavivirus. |
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