Meningitis

Alternative names:

bacterial meningitis; viral meningitis

Definition:

An infection which causes inflammation of the membranes covering the brain and spinal cord.

Causes, incidence, and risk factors:

The most common causes of meningitis are bacterial infections that start in other parts of the body and spread to the brain or spinal cord via the bloodstream. Meningitis is also caused by viruses, chemical irritation, or tumors.

Types include:

• meningitis, cryptococcal
• syphilitic aseptic meningitis
• meningitis, H. influenza
• meningitis; meningococcal
• meningitis, pneumococcal
• meningitis, staphylococcal
• meningitis, tuberculous
• aseptic meningitis
• meningitis gram negative

Acute bacterial meningitis is very serious and should be treated immediately to prevent permanent damage. Bacterial strains that cause meningitis include Streptococcus, Haemophilus influenzae, Staphylococcus, and Meningococcus. In the U.S. about 17,500 cases of bacterial meningitis occur each year.

Common viral meningitis is milder and occurs more often than bacterial meningitis. It usually develops in the winter and affects people under 30. Seventy percent of the infections occur in children under the age of 5. Other types of viral meningitis are rare, but more serious.