Case-fatality rate during a measles outbreak in eastern Niger in 2003

The World Health Organization (WHO) estimates that the case-fatality rate (CFR) for measles in West Africa is 4%-6%. In Niger, 50,138 measles cases and 201 deaths (CFR, 0.4%) were reported in 2003. We conducted an investigation to determine the epidemiology and the true CFR of measles in the Mirriah district in Niger.

Twenty-two villages from the Mirriah district that reported measles cases in 2003 were included in the investigation. A comprehensive household search for measles cases and deaths was conducted, and serum samples from 12 villages were collected for laboratory confirmation. A measles case was defined as illness characterized by fever, rash, and either cough, coryza, or conjunctivitis, with rash onset during the period from 1 January 2003 to 15 April 2003. Deaths occurring within 30 days after rash onset were attributed to measles unless they were obviously due to other causes.

Measles was confirmed serologically in all villages from which samples were collected. Of 945 case patients identified, 900 (95.2%) were aged <15 years, 114 (12.3%) were vaccinated, and 789 (83.5%) sought treatment at a health care facility. A total of 92 deaths were attributed to measles (CFR, 9.7%; 95% confidence interval, 7.9%-11.5%). The CFR was highest in infants aged <1 year (15.6%). Households with >or=2 case patients had a higher CFR (10.8%) than that of households with only 1 case patient (6.0%). Households consisting of >or=8 members had a CFR of 12.8%, whereas the CFR of smaller households was 7.1%.

This investigation suggests that the measles CFR in the Mirriah district may be 2-fold higher than the WHO regional estimate and 20-fold higher than the estimate derived from routine surveillance. Reducing measles mortality in Niger will require wide-age-range vaccination campaigns, improvement in routine immunization services, and periodic "follow-up" campaigns.