Meningitis is an inflammation of coverings (meninges) of the brain and spinal cord. Most often it is caused by a viral or bacterial infection. Other infectious agents such as fungi can also cause meningitis. Rarer causes of meningitis include atypical drug reactions and systemic lupus erythematosus. Viral, or aseptic, meningitis is the most common type. In general, viral meningitis is not directly contagious. Anyone can get viral meningitis, but it occurs most often in children. Many different viruses can cause meningitis; an enterovirus tends to be the usual culprit.
Viral meningitis due to enterovirus peaks in mid-summer through early autumn. But it can occur any time of the year. Except for the rare case of herpes meningitis, viral meningitis will resolve on its own after 7 to 10 days.
Bacterial meningitis, formerly called spinal meningitis, is a very serious and potentially fatal infection. It can strike very healthy people, but infants and older people are more susceptible. In the past, the three most common types of bacterial meningitis were caused by Neisseria meningitidis, Haemophilus influenza and Streptococcus pneumoniae. Now that we have very effective vaccines to help prevent all three types, bacterial meningitis in otherwise healthy children and adults occurs less often.
Besides infants and the elderly, people with chronic diseases and/or impaired immune systems have the greatest risk of meningitis caused by bacteria and fungi.