Meningococcus: Vaccine Preventable Diseases Surveillance Standards
Overview
Neisseria meningitidis (Nm) is a gram-negative
bacterium that usually resides harmlessly in the human
pharynx. Under certain conditions, asymptomatic
carriage can progress to invasive meningococcal disease
(IMD), resulting in meningitis, fulminant septicemia
or both. The majority of invasive infections are caused
by meningococci of serogroups A, B, C, X, W or Y
capsular polysaccharides. These serogroups can cause
both endemic disease and outbreaks, but their relative
prevalence varies considerably with time and geographic
location. In the African meningitis belt (from Senegal
in the west to Ethiopia in the east), serogroup A
has historically been the most important serogroup
causing large epidemics.
The recent epidemiology
of meningococcal disease in Africa is changing,
particularly in the wake of the introduction of the
conjugate serogroup A vaccine over the last decade;
in addition, outbreaks caused by serogroups C, W and
X have occurred more frequently in recent years. In
Europe, North America and Latin America, serogroups
B, C and W currently cause the majority of disease,
while in Asia, though surveillance data are limited,
serogroups A and C appear to cause most disease.