International Notes Epidemic Meningococcal Disease: Recommendations for Travelers to Nepal

During the first 6 months of 1983, an epidemic of serogroup A meningococcal meningitis, resulting in 875 cases and 95 deaths, occurred in the Kathmandu valley of Nepal. The overall annual attack rate was 103 cases per 100,000 population; the case-fatality ratio was 11%. The highest age-specific attack rate (223/100,000) was for children under 1 year of age; 83% of the cases occurred among persons under 25 years of age. The epidemic peaked in May and ended in June, coincident with the onset of the rainy season. No vaccination efforts were undertaken.

During December 1983 and January 1984, three times as many cases occurred in Kathmandu as in the same period a year previously; a mass vaccination campaign was initiated February 8, 1984. The target population included persons 1-24 years of age living in the Kathmandu valley. Three hundred thirty thousand doses of bivalent A/C meningococcal vaccine were given, achieving approximately 65% coverage of the target population. A dramatic decline in the number of meningitis cases occurred coincident with the initiation of the mass vaccination campaign.

Surveillance in 1985 indicates that meningococcal meningitis is occurring at a much lower rate than in 1984. However, meningococcal disease among hikers is now being recognized. Between January 1984 and January 1985, two culture-confirmed and four clinically suspected cases of meningococcal disease have been documented among tourists from western countries traveling in Nepal. Three of these occurred between January and April 1984, and three occurred between November 1984 and January 1985. Patients' ages ranged from 16 years to 40 years (mean 27 years). Five patients had evidence of meningococcemia; the other had meningitis alone. Two (33%) died. All became ill during or shortly after hiking outside Kathmandu. The patients' countries of origin were the United States (three patients), Australia (two), and Switzerland (one). Reported by Div of Bacterial Diseases, Center for Infectious Diseases, Div of Immunization, Div of Quarantine, Center for Prevention Services, CDC.

Editorial Note

Editorial Note: Epidemic meningococcal disease has not been reported previously in Nepal, and, except for Mongolia and Vietnam, has been reported in no other Asian country (1,2). Large epidemics of group A meningococcal disease have occurred primarily in the "meningitis belt" of Africa, which consists of the semiarid Sahelian zone south of the Sahara (3). In Africa, epidemics have been cyclic, occurring every 10-12 years and lasting 2-3 years. The epidemics occur during the dry season and stop when the rains begin. The seasonal pattern of disease seen in Nepal is similar to that observed in Africa, although Nepal's dry season is cold rather than hot.

Meningococcal polysaccharide vaccines have been used to control epidemics in the past (4-6). In the immunization campaign in the Kathmandu valley, the target population was selected to cover the age group in which 75% of the cases were occurring. Although at high risk, children under 1 year of age were not vaccinated because the vaccine is poorly immunogenic in that age group.

Based on the 1983 tourist statistics, approximately 105,000 non-Asian tourists visit Nepal each year. Thus, the attack rate for such tourists during the past year was 6/100,000. Based on the number of hiking permits issued (32,298), the attack rate for hikers was 19/100,000. By comparison, the annual incidence of meningococcal disease in this age group in the United States is approximately 0.3/100,000 (7). The relative increase in risk is even more striking when the average length of stay for tourists in Nepal (11 days) is taken into account, since the attack rate for the disease in the United States for 11 days would be only .009/100,000. Because of the risk of meningococcal disease among hikers, CDC recommends that tourists planning to hike in Nepal receive meningococcal vaccine. Although all cases of meningococcal disease to date have occurred in hikers, it is prudent for other travelers to Nepal to receive the vaccine also.

The serogroup A meningococcal vaccine has a clinical efficacy of 85%-95% for at least 1 year, with protection achieved 1-2 weeks after vaccination. Adverse reactions are limited to local erythema or soreness. There are two formulations of meningococcal vaccine currently available in the United States: the bivalent A-C vaccine and the quadrivalent A,C,Y,W-135 vaccine. Either formulation will give protection against serogroup A meningococcal disease; the bivalent vaccine is less expensive. The sole distributor of these vaccines in the United States is Squibb. The vaccine can be obtained through a pharmacy by contacting a Squibb regional distribution center or by calling Squibb at (800) 822-2463. Because meningococcal vaccine is inactivated, it can be administered simultaneously, if necessary, with other live or inactivated vaccines needed for foreign travel. Immunoglobulin, if needed, should not interfere with the immune response.

Because immunity is not achieved until 1-2 weeks postvaccination, CDC recommends that tourists be vaccinated before departure. However, vaccine is available in Nepal at the Epidemiology Division, Department of Health Services, Teku, Kathmandu. Questions concerning meningococcal disease in Nepal and recommendations for vaccination should be addressed to the Respiratory and Special Pathogens Epidemiology Branch, Division of Bacterial Diseases, Center for Infectious Diseases, CDC, telephone (404) 329-3687.

References

1. Jamba G, Bytchenko B, Causse G, et al. Immunization during a cerebrospinal meningitis epidemic in the Mongolian People's Republic, 1974-75. Bull WHO 1979;57:943-6.

2. Oberti J, Hoi NT, Caravano R, Tan CM, Roux J. Etude d'une }pid}mie de m}ningococcie au Viet Nam (provinces du sud). Bull WHO 1981;59:585-90.

3. Galazka A. Meningococcal disease and its control with meningococcal polysaccharide vaccines. Bull WHO 1982;60:1-7.

4. Bosmans E, Vimont-Vicary P, Andre FE, Crooy PJ, Roelants P, Vandepitte J. Protective efficacy of a bivalent (A+C) meningococcal vaccine during a cerebrospinal meningitis epidemic in Rwanda. Ann Soc Belg Med Trop 1980;60:297-306.

5. Peltola H. Group A meningococcal polysaccharide vaccine and course of the group A meningococcal epidemic in Finland. Scand J Infect Dis 1978;10:41-4.

6. Greenwood BM, Wali SS. Control of meningococcal infection in the African meningitis belt by selective vaccination. Lancet 1980;I:729-32.

7. Band JD, Chamberland ME, Platt T, Weaver RE, Thornsberry C, Fraser DW. Trends in meningococcal disease in the United States, 1975-1980. J Infect Dis 1983;148:754-8.

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