Neisseria meningitides outbreak-Harenabuluk District, Ethiopia, 2011
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Background: Neisseria meningitides outbreaks occur yearly with >3000 cases/year and case fatality (CFR) of 1.4-8.5% in Ethiopia, a country within the "meningitis belt" of Sub-Saharan African. In February 2011, a cluster of suspected meningitis cases was detected in Harenabuluk outside the classical meningitis belt areas of Ethiopia. We investigated to confirm the outbreak, identify etiologic agent, determine risk factors, and establish control measures.
Methods: Descriptive study followed by case-control study, introducing structured questionnaires to both patients and controls. Meningitis cases were defined as a person from Harenabuluk in which Neisseria meningitides was isolated by bacterial culture declared from cerebrospinal fluid specimens between 02/02-17/03/2011. Age and sex matched controls were selected from the neighbor of cases with the ratio of 1:1. Climate data was collected to analyze climate anomalies. Adjusted odds ratios are given with 95% of confidence interval (CI). Using bivariate and multivariate analysis, we compared exposures for meningitis.
Results: We enrolled 49 cases and 49 controls. An overall attack rate (AR) was 61/10,000 with CFR of 8/1000. The high AR of 115/10,000 was observed among 20-29 years old. The bivariate analysis identified nine risk factors. In multivariate model, attendance at Koran teaching place (odd ratio [OR] =6.1, 95% CI =2.5-15.2), exposure to dust (OR= 6.7, 95% CI: 2.7-16.6), living in one house with more than four peoples (OR=3.9, 95% CI: 1.6-11), having no ventilation (OR=5.3, 95% CI: 2-13) were associated. Climate data revealed monthly climate anomalies.
Conclusion: We confirmed meningitis outbreak showed two unusual characteristics: geographical location outside the meningitis belt area and high age specific AR among 20-29 years old. The occurrence of the outbreak and the identified meningitis risk factors, demonstrate that meningitis outbreaks are possible in all situations once meningitis has been introduced. Our recommendations led to start vaccination and active surveillance with monthly health education on meningitis and risk factors by the district health workers.