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Definition Return to top
Meningitis is an infection which causes inflammation of the membranes covering the brain and spinal cord. Non-bacterial meningitis is often referred to as "aseptic meningitis." Bacterial meningitis may be referred to as "purulent meningitis."Causes, incidence, and risk factors Return to top
The most common causes of meningitis are viral infections that usually resolve without treatment. However, bacterial infections of the meninges are extremely serious illnesses, and may result in death or brain damage even if treated. Meningitis is also caused by fungi, chemical irritation or drug allergies, and tumors.
Types include:
Acute bacterial meningitis is a true medical emergency, and requires immediate hospital-based treatment. Bacterial strains that cause meningitis include Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis (meningococcus), Listeria monocytogenes, and many other types of bacteria. In the U.S. about 17,500 cases of bacterial meningitis occur each year.
Viral meningitis is milder and occurs more often than bacterial meningitis. It usually develops in the late summer and early fall, often affects children and adults under 30. Seventy percent of the infections occur in children under the age of 5. Most viral meningitis is associated with enteroviruses, which are viruses that commonly cause stomach flu.
However, many other types of viruses can also cause meningitis; for example, viral meningitis may occur as a complication in people with genital herpes. Recently, West Nile virus spread by mosquito bites has become a cause of viral meningitis in most of the U.S. In addition to causing viral meningitis, West Nile virus can cause encephalitis in some patients and a polio-like syndrome in others.
Symptoms Return to top
Meningitis is an important cause of fever in newborn children. For this reason, a lumbar puncture is often done on newborns who have a fever of uncertain origin.
Signs and tests Return to top
Treatment Return to top
Antibiotics will be prescribed for bacterial meningitis; the type will vary depending on the infecting organism. Antibiotics are ineffective in viral meningitis. Treatment of secondary symptoms including brain swelling, shock, and convulsions will require other medications and intravenous fluids. Hospitalization may be required depending on the severity of the illness and the needed treatment.Expectations (prognosis) Return to top
Early diagnosis and treatment of bacterial meningitis is essential to prevent permanent neurological damage. Viral meningitis is usually not serious, and symptoms should disappear within 2 weeks with no residual complications.Complications Return to top
Calling your health care provider Return to top
If you feel that you or your child have symptoms suggestive of meningitis, you must seek emergency medical help immediately. Early treatment is key to a good outcome.Prevention Return to top
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Page last updated: 28 October 2004 |