Widening the Meningitis Belt

Abstract & Commentary

Synopsis: Careful evaluation of epidemiologic data from recent African outbreaks of meningococcal disease suggests that significant risks now extend beyond the sub-Saharan "belt" through the Rift Valley and Great Lakes regions into Mozambique, then into Namibia and Angola.

Source: Molesworth AM, et al. Where is the meningitis belt? Defining an area at risk of epidemic meningitis in Africa. Trans R Soc Trop Med Hyg. 2002;96:242-249.

Since 1963, people have recognized the presence of a belt-like band across Africa wherein meningococcal epidemics are common. Over the past 2 decades, however, there have been several waves of severe epidemics in African regions outside the "belt." British researchers thoroughly reviewed outbreak reports of Neisseria meningitidis disease in Africa from 1980 through mid-2001. They both mapped outbreaks and calculated incidence rates.

A total of 114 outbreaks were identified. Group A meningococcus was most commonly the cause, and clone III-1 has been predominant since 1988. Figure 1 shows the traditional "Meningitis Belt," while Figure 2 demonstrates the areas in which the current study found high incidences of meningococcal disease. While the brunt of the meningitis burden still occurs in the traditional "belt," there is significant disease in other parts of Africa. Interestingly, the mapping of meningitis epidemics corresponds to areas with annual rainfall rates ranging from 30-110 cm. Alterations in climate and forests during the past 2 decades might be changing the epidemiology of meningococcal disease in Africa.

 

Comment by Philip R. Fischer, MD, DTM&H

Meningococcal disease can be devastating both to individuals and to populations. While it is difficult to extrapolate from indigenous reports of disease risk for travelers, the report from Dr. Molesworth and colleagues suggest we might need to enlarge our view of risk areas in Africa. Outbreaks of meningitis (N meningitidis serogroup A) in the "Great Lakes Region" of Burundi, Rwanda, and Tanzania were reported in September 20021 and confirm that the risk for meningitis epidemics extends well beyond the original geographic "belt."

Travel medicine practitioners use a variety of resources to guide their advice to travelers. While commercial groups and organizations such as CDC and WHO periodically update their recommendations, all individuals providing pretravel care should be aware that there is a growing risk of meningococcal disease outside the traditional "belt" across Africa. Especially for those travelers anticipating contact with at-risk groups (crowded villages and refugee camps, dormitory populations, health care settings), there could be consideration given to meningococcal vaccination prior to any trip within the widened meningitis "belt" of Africa.

Meningococcal vaccines vary in different parts of the world. Americans have had access to the quadrivalent (A, C, Y, W135) vaccine, and others have sometimes used vaccines that "only" cover serogroups A and/or C. While most African outbreaks are caused by serogroup A, there has been an increase in serogroup W135 infection in travelers to Saudi Arabia. Some Hajj pilgrims received vaccinations, but without W135 protection, and then transmitted meningococcus to contacts following their trips.2 When available, the quadrivalent vaccine should be used for travelers to Saudi Arabia (and is indeed now required).3

Pretravel consultations also provide an opportunity to review the adequacy of "routine" immunizations, and such "routine" schedules have changed in recent years. Meningococcal vaccine is now recommended by some groups for American college freshmen who will be living in dormitories.4 In the United Kingdom, a conjugate meningococcal C vaccine that is more effective than the older polysaccharide vaccine, when used in young children, is now part of the primary immunization program.5

Dr. Fischer, Professor of Pediatrics, Department of Pediatric & Adolescent Medicine, Mayo Clinic, Rochester, MN, is Associate Editor of Travel Medicine Advisor.

References

1. WHO CSR and Epidemiological Bulletin (e-mail), 4 September 2002 as reported on www.who.int/disease-outbreak-news/

2. Wilder-Smith A, et al. Acquisition of W135 meningococcal carriage in Hajj pilgrims and transmission to household contacts: Prospective study. BMJ. 2002;325: 365-366.

3. Memish ZA. Meningococcal disease and travel. Clin Infect Dis. 2002;34:84-90.

4. Rosenstein NE, et al. Meningococcal vaccines. Infect Dis Clin North Am. 2001;15:155-169.

5. Soriano-Gabarro M, et al. Vaccines for the prevention of meningococcal disease in children. Semin Pediatr Infect Dis. 2002;13:182-189.