Global Distribution of Invasive Meningococcal Disease by Serogroup (A, B, C, W-135, X, Y)

Meningococcal disease incidence differs geographically, and the reason behind this variation is not clear. Distribution of N meningitidis serogroups varies widely from one part of the globe to the other (Figure 8). In Europe, South America, and Australia, serogroups B and C predominate, whereas in Asia, serogroups A and C are the most common. In North America, most meningococcal disease is caused by serogroups B, C, and Y.3 Although  serogroup W-135 also causes a substantial proportion of meningococcal disease in Africa, serogroup A—the serogroup responsible for the larger epidemics—is responsible for most cases in the meningitis belt and in the expanded epidemic-susceptible region.1-4

Serogroup-Specific Meningococcal Disease Estimated Incidence in the United States

Currently in the United States, meningococcal disease is commonly caused by serogroups B, C, and Y. As per a laboratory-based surveillance performed in the United States for meningococcal disease in 2009 (Figure 9), serogroup Y accounted for approximately 40% of the disease.5 Recent data from 2009 demonstrate that serogroup B causes most cases of meningococcal disease in infants below the age of 1 year (Figure 10).5


Changing Serogroup Distribution Over Time in the United States

Over the past 20 years in the United States, serogroups B, C, and Y have caused the most meningococcal disease, but the proportion has varied by serogroup. Serogroup Y is now the most common serogroup in the United States.5 The proportion of meningococcal disease caused by serogroup Y increased dramatically from 2% of reported cases in 1989 to 36% of reported cases in 2009 (Figure 11).5,18 Serogroup A was once predominant in the United States but is now rarely reported.

Studies from 1989 to 1991 show maximum prevalence of serogroups B and C (46% and 45%) in the United States, whereas serogroups Y and W-135 were very low, accounting for only 2% and 7% of cases, respectively. In 1998, the proportion of disease caused by serogroups Y and W-135 increased to 33% and 17%, respectively, whereas the rates of proportion of disease caused of serogroups B and C dropped to 27% and 23%, respectively. In 2009, a different scenario can be seen again. The proportion of disease caused by serogroup Y further increased to 36%, while the cases caused by W-135 and other serogroups were reduced to 4%.5,18

Estimated Incidence of Meningococcal Disease by Serogroup in Infants and Adolescents

In the years from 1998 to 2007, a total of 2262 cases of meningococcal disease were reported in the United States, resulting in an estimated US average incidence of 0.53 cases per 100,000 population.19

The estimated incidence of serogroups B and Y was highest in children below the age of 2 years. Importantly, regardless of the serogroup variability by age, as illustrated by Figure 12, the estimated incidence of meningococcal disease caused by all serogroups is highest in infants.19


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