Causes, incidence, and risk factorsThe 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
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.
SymptomsSymptoms 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)
- Bulging fontanelles
- Decreased consciousness
- Poor feeding or irritability in children
- Rapid breathing
- Unusual posture, with the head and neck arched backwards (opisthotonos)
People cannot tell if they have bacterial or viral meningitis by how they feel, so they should seek prompt medical attention.
Signs and testsPhysical examination will usually show:
- Fast heart rate
- Mental status changes
- Stiff neck
Tests that may be done include:
- Blood culture
- Chest x-ray
- CSF examination for cell count, glucose, and protein
- CT scan of the head
- Gram stain, other special stains, and culture of CSF
TreatmentDoctors 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.
Expectations (prognosis)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.
- Brain damage
- Buildup of fluid between the skull and brain (subdural effusion)
- Hearing loss
Calling your health care providerIf 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.
- 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).
Routinely giving infants a new vaccine that guards against meningitis appears to be effective, a new study indicates.
The multi-center clinical trial of almost 1,900 infants found that administration of routine infant immunizations with a vaccine for serogroup B Neisseria meningitidis -- a bacterium that can cause serious disease such as sepsis and meningitis -- was effective against meningococcal strains and caused minimal interference with infants' response to routine vaccinations.
The study of the multi-component serogroup B meningococcal vaccine (4CMenB) was funded by Novartis Vaccines and Diagnostics and appears in the Feb. 8 issue of the Journal of the American Medical Association.
"In conclusion, 4CMenB was "immunogenic [able to produce an immune response], generally well tolerated, and showed minimal interference with routine vaccines in the first year of life," wrote Dr. Nicoletta Gossger, of the University of Oxford in England, and colleagues.
Meningitis is an inflammation of the membranes covering the spinal cord and the brain. According to the U.S. Centers for Disease Control and Prevention, meningitis can be caused by a virus or a bacteria. The bacterial form is often more severe and can result in brain damage, hearing loss and death.
Before the 1990s, Haemophilus influenzae type b (Hib) was the leading cause of bacterial meningitis. Today, the Hib vaccine is part of routine pediatric immunizations.
In the U.S., meningococcal disease is usually caused by groups A, B, C, Y, and W-135 of the meningococcus bacteria. Currently, licensed vaccines provide some protection against all groups except B. There is no licensed vaccine for group B in the U.S, according to the U.S. National Network for Immunization Information.
If the new vaccine were to be licensed, "this vaccine could potentially provide improved protection for infants against meningococcal disease beyond the protection provided by currently licensed vaccines," the researchers noted.
In an accompanying editorial, experts from the U.S. Centers for Disease Control and Prevention said 4CMenB has the potential to reduce serogroup B meningococcal disease substantially. "But it cannot be compared with the success of conjugate vaccine programs," they wrote.
Despite its potential, 4CMenB vaccine may have some limitations, the editorialists wrote. It may not be as effective as a vaccine against serogroup C was in the United Kingdom, and it remains to be seen if booster doses will be required to sustain protection, while adding serogroup B vaccination will also add additional costs to the infant vaccine schedule.
"However, the anticipated licensure of this vaccine in Europe and other countries means that for the first time vaccines to prevent all five of the serogroups that cause most meningococcal disease worldwide will be available," the CDC doctors wrote.
Journal of the American Medical Association, news release, Feb. 7, 2012
Swartz MN. Meningitis: bacterial, viral, and other. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 437.