Meningitis is most often caused by a bacterial or viral infection that moves into the cerebral spinal fluid (CSF). CSF is the fluid that protects and cushions the brain and spinal cord. A fungus or parasite may also cause meningitis. This is more common only in children with a weak immune system.
Meningitis caused by a virus is more common and usually less severe. Bacterial meningitis is usually more severe and may lead to long-term complications or death.
Viruses that can cause meningitis include the herpes simplex virus, the mumps virus (paramyxovirus), the flu virus and West Nile virus.
Bacteria that can cause meningitis include group B streptococcus, E. coli, Haemophilus influenzae type b (Hib) and a strep bacteria that causes pneumonia. Syphilis, tuberculosis, and Lyme disease bacteria can also cause meningitis.
The bacteria, viruses and fungi that cause meningitis usually grow in a person’s respiratory tract. A child may have no symptoms at all but may carry the organism in his or her nose and throat. They may be spread by:
- Close contact with someone carrying the infection
- Touching infected objects, such as doorknobs, hard surfaces, or toys, and then touching nose, mouth or eyes
- Droplets from a sneeze, close conversation or kissing
An infection usually starts in the respiratory tract. In a child, it may first cause a cold, sinus infection or ear infection. It can then go into the bloodstream and reach the brain and spinal cord.