Meningitis and meningococcal meningitis information

Strains make a world of difference

The Neisseria meningitidis bacteria can lead to meningococcal meningitis. And this bacterium is complex, because there are different disease-causing strains (also called serogroups). It’s these strains that circulate in the population. The 5 strains that account for almost all cases of meningococcal meningitis are A, B, C, Y, and W-135.

Strains are the traveling types

As you can see from the map below, the presence of particular Neisseria meningitidis strains differs from place to place worldwide. As people travel from one place to another—and unknowingly infect others—this distribution of strains changes over time and by location. So there's a growing need to protect against as many of these strains as possible through vaccination.

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In the United States: a real-world example

In the United States, the proportion of strains causing meningococcal disease has changed in less than 20 years. For example, meningococcal disease caused by strain Y has increased from 9% to 35% of cases during this time frame. See these changes for yourself by clicking on the different time periods below.

Home Meningococcal meningitis Meningococcal meningitis & bloodstream infection Strains of bacteria The history of meningococcal meningitis Causes of meningitis Who’s at risk? Symptoms & treatment Preventing meningitis Vaccination schedule Resources & links	Strains make a world of difference The *Neisseria meningitidis* bacteria can lead to meningococcal meningitis. And this bacterium is complex, because there are different disease-causing strains (also called serogroups). It’s these strains that circulate in the population. The 5 strains that account for almost all cases of meningococcal meningitis are A, B, C, Y, and W-135. Strains are the traveling types As you can see from the map below, the presence of particular Neisseria meningitidis strains differs from place to place worldwide. As people travel from one place to another—and unknowingly infect others—this distribution of strains changes over time and by location. So there's a growing need to protect against as many of these strains as possible through vaccination. In the United States: a real-world example In the United States, the proportion of strains causing meningococcal disease has changed in less than 20 years. For example, meningococcal disease caused by strain Y has increased from 9% to 35% of cases during this time frame. See these changes for yourself by clicking on the different time periods below.
	In the United States
	Throughout the world: a global perspective Meningococcal meningitis occurs from time to time in small clusters throughout the world—with seasonal variations. Outbreaks associated with strain W-135 have tended to occur in the Middle East and sub-Saharan Africa (the "meningitis belt"). And the A strain is also common in sub-Saharan Africa. Outbreaks caused by the Y strain have occurred in Israel, Latin America, and the United States. Starting in 1991, New Zealand experienced an epidemic of the B strain. Persistent epidemics of the B strain have also occurred in Cuba, Colombia, Brazil, Chile, Norway, and the United States. Changes in strains have impact As you can see, the proportion of strains responsible for most cases of disease varies over time and by location. These differences impact government recommendations for vaccination against meningococcal meningitis. That's because vaccines protect against specific strains, so vaccination programs are usually based on how to best protect people depending on the strains that are common where they live or where they're going to travel.
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