Meningitis is a bacterial infection of the membranes covering the brain and spinal cord (meninges).
Causes, incidence, and risk factors
The most common causes of meningitis are viral infections that usually get better without treatment. However, bacterial meningitis infections are extremely serious, and may result in death or brain damage, even if treated.
Meningitis may also be caused by:
Most viral meningitis is due to enteroviruses, which are viruses that also can cause intestinal illness.
Many other types of viruses can cause meningitis.
Viral meningitis can be caused by herpes viruses, the same virus that can cause cold sores and genital herpes . However, people with cold sores or genital herpes are not at a greater risk of developing herpes meningitis.
Viruses that cause mumps and HIV can cause aseptic meningitis.
Recently, West Nile virus, spread by mosquito bites, has become a cause of viral meningitis in most of the United States.
Viral meningitis occurs more often than bacterial meningitis, and is milder. It usually occurs in the late summer and early fall. It most often affects children and adults under age 30.
Bacteria meningitis is an emergency. You will need immediate treatment in a hospital. Symptoms usually come on quickly, and may include:
Antibiotics are used to treat bacterial meningitis. The specific type depends on which bacteria is causing the infection. Antibiotics do not treat viral meningitis.
Antiviral medicine may be given to those with herpes meningitis.
Other treatments will include:
Fluids through a vein (IV)
Medicines to treat symptoms such as brain swelling, shock, and seizures
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 lasting complications.
Tunkel AR, Van de Beek D, Scheld WM. Acute meningitis. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009: chap 84.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.