Meningitis is an inflammation (swelling) of the protective membranes covering the brain and spinal cord known as the meninges. This inflammation is usually caused by an infection of the fluid surrounding the brain and spinal cord.
Meningitis is usually caused by bacteria or viruses, but can be a result of injury, cancer, or certain drugs.
It is important to know the specific cause of meningitis because the treatment differs depending on the cause.
Meningitis caused by viruses, like enteroviruses, arboviruses and herpes simplex viruses, is serious but often is less severe than bacterial meningitis, and people with normal immune systems usually get better on their own. There are vaccines to prevent some kinds of viral meningitis.
Fungal meningitis is caused by fungi like Cryptococcus and Histoplasma and is usually acquired by inhaling fungal spores from the environment. People with certain medical conditions like diabetes, cancer, or HIV are at higher risk of fungal meningitis.
Various parasites can cause meningitis or can affect the brain or nervous system in other ways. Overall, parasitic meningitis is much less common than viral and bacterial meningitis.
Primary amebic meningoencephalitis (PAM) is a rare and devastating infection of the brain that is caused by a free-living microscopic ameba called Naegleria fowleri which is found naturally in warm water and soil.
Sometimes meningitis is not spread from person to person, but is instead caused by cancers, systemic lupus erythematosus (lupus), certain drugs, head injury, and brain surgery.
How it Spreads
Bacterial meningitis is spread from person to person. The bacteria are spread by exchanging respiratory and throat secretions (saliva or spit) during close (for example, coughing or kissing) or lengthy contact, especially if living in the same household.
If you have close contact with a person who has viral meningitis, you may become infected with the virus that made the person sick. However, you are probably not likely to develop meningitis from the illness. That’s because only a small number of people who get infected with the viruses that cause meningitis will actually develop meningitis.