Skip to Main Content


Definitions and Epidemiology


Meningitis is defined as an inflammation of the leptomeninges by any cause. Bacteria cause meningitis by invading and replicating in the subarachnoid space and cause significant morbidity and mortality. Viral infections may also cause meningitis, mostly commonly enteroviruses, but few children with viral meningitis suffer any long-term sequelae. Therefore the focus of this chapter will be on bacterial meningitis. Figure 16-1 gives the age, organism, and specific rates of bacterial meningitis in the United States prior to the introduction of currently used conjugate vaccines (note the y-axis is a log scale). As can be seen, the greatest risk period for bacterial meningitis is in the first 6 months of life.


Overall, there has been a remarkable decline in the rate of bacterial meningitis in the developed world over the last 2 decades with the introduction of the Haemophilus influenzae type b conjugate vaccines, the Streptococcus pneumoniae conjugate vaccines, and greater use of meningococcal vaccines. Haemophilus influenzae type b was once the leading cause of bacterial meningitis in children but has been virtually eliminated in countries utilizing the conjugate vaccine. In the first 2 months of life, Enterobacteriaceae (eg, E. coli, Klebsiella species), group B streptococci, and occasionally Listeria monocytogenes, Salmonella species, or enterococci will cause bacterial meningitis. Infections due to S pneumoniae occur with increasing in frequency over the second month to become the most likely cause of bacterial meningitis, and continue to increase in frequency until 4 or 5 months of age when they begin to decline. Neisseria meningitidis is the most common cause of bacterial meningitis by 1 year of age. S pneumoniae remains the second most common cause after 1 year of age, and all other pathogens trail behind considerably. These two pathogens occur more commonly in the winter months, presumably in association with common respiratory viruses that disrupt mucosal barriers, thereby allowing these colonizing pathogens to move from the nasopharynx to the bloodstream more easily. Research is ongoing to develop vaccines that will be effective against a greater number of pneumococcal serotypes and improved meningococcal vaccines that may work for younger children and against group B strains. Table 16-1 reviews microbial causes of meningitis.

Figure 16-1.
Graphic Jump Location

Incidence rates of bacterial meningitis by age and pathogen prior to the introduction of the conjugate Haemophilus influenzae type b and heptavalent S-pneumoniae vaccines. (From Wenger JD, Hightower AW, Facklam RR, Gaventa S, Broome CV, eds. Bacterial meningitis in the United States, 1986: report of a multistate surveillance study. The Bacterial Meningitis Study Group. J Infect Dis. 1990;162:1316-1323.)

Table Graphic Jump Location
Table 16–1. Etiology of Meningitis

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.


About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.