Meningitis (muh-nin-JI-tis) is the inflammation of the meninges, the membranes covering the brain and spinal cord. The infection can be caused by either viruses or bacteria. Viral meningitis is more common but has less serious debilitating health consequences and is treated only symptomatically. People with viral meningitis often recover without medical treatment. There are no vaccines to protect a person from viral meningitis.

Meningococcal meningitis is caused by Neisseria meningitidis bacteria. The bacteria reside in the nasal and throat passages of approximately 15-25% of the general population, at any given time, and have the potential of causing epidemics.

When the infection invades the blood, it is called septicemia (general terminology). When the infection is caused by the meningococcal bacteria, it is called meningococcemia.