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Since 2010, the introduction of an effective serogroup A meningococcal conjugate vaccine has led to the near-elimination of invasive Neisseria meningitidis serogroup A disease in Africa’s meningitis belt. However, a significant burden of disease and epidemics due to other bacterial meningitis pathogens remain in the region. High-quality surveillance data with laboratory confirmation is important to monitor circulating bacterial meningitis pathogens and design appropriate interventions, but complete testing of all reported cases is often infeasible. Here, we use case-based surveillance data from 5 countries in the meningitis belt to determine how accurately estimates of the distribution of causative pathogens would represent the true distribution under different laboratory testing strategies. Detailed case-based surveillance data was collected by the MenAfriNet surveillance consortium in up to 3 seasons from participating districts in 5 countries. For each unique country-season pair, we simulated the accuracy of laboratory surveillance by repeatedly drawing subsets of tested cases and calculating the margin of error of the estimated proportion of cases caused by each pathogen (the greatest pathogen-specific absolute error in proportions between the subset and the full set of cases). Across the 12 country-season pairs analyzed, the 95% credible intervals around estimates of the proportion of cases caused by each pathogen had median widths of ±0.13, ±0.07, and ±0.05, respectively, when random samples of 25%, 50%, and 75% of cases were selected for testing. The level of geographic stratification in the sampling process did not meaningfully affect accuracy estimates. These findings can inform testing thresholds for laboratory surveillance programs in the meningitis belt.

Background The MenAfriNet consortium was established in 2014 to support implementation of case-based meningitis surveillance in 5 countries in the meningitis belt of sub-Saharan Africa: Burkina Faso, Chad, Mali, Niger, and Togo. Assessing surveillance performance is critical for interpretation of the collected data and implementation of future surveillance-strengthening initiatives. Methods Detailed epidemiologic and laboratory data were collected on suspected meningitis cases through case-based meningitis surveillance in participating districts in 5 countries. Performance of case-based surveillance was evaluated through sensitivity of case ascertainment in case-based versus aggregate meningitis surveillance and an analysis of surveillance indicators. Results From 2015 to 2017, 18 262 suspected meningitis cases were identified through case-based surveillance and 16 262 were identified through aggregate surveillance, for a case ascertainment sensitivity of 112.3%. Among suspected cases, 16 885 (92.5%) had a cerebrospinal fluid (CSF) specimen collected, 13 625 (80.7%) of which were received at a national reference laboratory. Among these, 13 439 (98.6%) underwent confirmatory testing, and, of those tested, 4371 (32.5%) were confirmed for a bacterial pathogen. Conclusions Overall strong performance for case ascertainment, CSF collection, and laboratory confirmation provide evidence for the quality of MenAfriNet case-based surveillance in evaluating epidemiologic trends and informing future vaccination strategies.

Background. 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. Methods. 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. Results. 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 2 case patients had a higher CFR (10.8%) than that of households with only 1 case patient (6.0%). Households consisting of 8 members had a CFR of 12.8%, whereas the CFR of smaller households was 7.1%. Conclusions. 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. Measles continues to cause high morbidity and mortality