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:
- Chemical irritation
- Drug allergies
- Aseptic meningitis
- Cryptococcal meningitis
- Gram negative meningitis
- H. influenza meningitis
- Meningitis due to cancer (carcinomatous meningitis)
- Meningococcal meningitis
- Pneumococcal meningitis
- Staphylococcal meningitis
- Syphilitic aseptic meningitis
- Tuberculous meningitis
Acute bacterial meningitis is a medical emergency, and requires immediate treatment in a hospital.
Viral meningitis is milder and occurs more often than bacterial meningitis. It usually develops in the late summer and early fall, and often affects children and adults under age 30. Most infections occur in children under age 5. Most viral meningitis is due to enteroviruses, which are viruses that also can cause intestinal illness.
Many other types of viruses can cause meningitis. For example, viral meningitis can be caused by herpes viruses, the same virus that can cause cold sores and genital herpes (although people with cold sores or genital herpes are not at a greater risk of developing herpes meningitis).
Recently, West Nile virus, spread by mosquito bites, has become a cause of viral meningitis in most of the United States.
Symptoms usually come on quickly, and may include:
- Fever and chills
- Mental status changes
- Nausea and vomiting
- Sensitivity to light (photophobia)
- Severe headache
- Stiff neck (meningismus)
Other symptoms that can occur with this disease:
- Bulging fontanelles
- Decreased consciousness
- Poor feeding or irritability in children
- Rapid breathing
- Unusual posture, with the head and neck arched backwards (opisthotonos)
Meningitis is an important cause of fever in children and newborns.
People cannot tell if they have bacterial or viral meningitis by how they feel, so they should seek prompt medical attention.
Signs and tests
Physical examination will usually show:
- Fast heart rate
- Mental status changes
- Stiff neck
For any patient who is suspected of having meningitis, it is important to perform a lumbar puncture ("spinal tap"), in which spinal fluid (known as cerebrospinal fluid, or CSF) is collected for testing.
Tests that may be done include:
Doctors prescribe antibiotics for bacterial meningitis. The type will vary depending on the bacteria causing the infection. Antibiotics are not effective in viral meningitis.
Other medications and intravenous fluids will be used to treat symptoms such as brain swelling, shock, and seizures. Some people may need to stay in the hospital, depending on the severity of the illness and the treatment needed.
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.
Calling your health care provider
If you think that you or your child has symptoms of meningitis, get emergency medical help immediately. Early treatment is key to a good outcome.
- Haemophilus vaccine (HiB vaccine) in children will help prevent one type of meningitis.
- The pneumococcal conjugate vaccine is now a routine childhood immunization and is very effective at preventing pneumococcal meningitis.
- Household members and others in close contact with people who have meningococcal meningitis should receive preventive antibiotics to avoid becoming infected themselves.
The meningococcal vaccination is recommended for:
- Adolescents ages 11 - 12 and adolescents entering high school (about age 15) who have not already received the vaccination.
- All college freshmen who have not been vaccinated and are living in dorms.
- Children age 2 and older who do not have their spleen or who have other problems with their immune system.
- Those traveling to countries where diseases caused by meningococcus are very common (ask your doctor).
Some communities conduct vaccination campaigns after an outbreak of meningococcal meningitis.
Swartz MN. Meningitis: bacterial, viral, and other. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 437.
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, PhD, MD, 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., Inc.