Basics
Meningitis is an inflammation of the meninges, the membranes that surround the brain and spinal cord Figure 01. Meningitis, a common disease worldwide, is relatively uncommon in the United States. Meningitis can result from either a bacterial or a viral infection, or from noninfectious diseases such as cancer and sarcoidosis. Meningitis affects people of all age groups; however, children, the elderly, and people with compromised immune systems are most at risk. Meningitis can appear abruptly, and the illness can last from 48 hours to several weeks.
Figure 01. Meninges
Chronic meningitis, which is a brain infection that causes inflammation of the meninges, can last a month or longer.
While the symptoms are similar, bacterial meningitis is much more serious than viral meningitis. Any symptoms of meningitis should be treated as a medical emergency. If you suspect that you have meningitis of either type, you must contact your doctor. Bacterial meningitis requires hospitalization, and, if untreated, can lead to severe disability or death.
Causes
Meningitis can be caused by various types of bacteria or viruses. Infectious organisms—bacteria, viruses, or fungi—travel through the bloodstream into the space between the meninges, resulting in an infection. Bacterial meningitis often follows an infection of the middle ear, sinuses, or upper respiratory tract, or pneumonia. Head trauma or neurosurgery can also allow bacteria to pass into the meninges, triggering an infection.
Viral meningitis (also called aseptic meningitis) is primarily caused by a group of viruses called enteroviruses.
Chronic meningitis is caused by slow-growing organisms such as fungi, or the bacteria that cause tuberculosis. Chronic meningitis is often a problem for people who are immunocompromised, such as those with AIDS, cancer, Lyme disease, syphilis, cytomegalovirus infection, or those who have used prednisone for a long period of time.
Viral meningitis, the more common yet less serious form, is contagious. Viruses responsible for meningitis are airborne, and can therefore be transmitted from person to person. For this reason, outbreaks of viral meningitis sometimes occur in epidemic-like waves.
Some of the bacteria responsible for bacterial meningitis, on the other hand, are normally present in the environment, and may even exist in your body without causing harm.
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I'm Kristen Dore, PharmD. Welcome to PDR Health!