Abstract
Meningococcal meningitis is a major public health problem that kills thousands annually in Africa, Europe, North, and South America. Occurrence is, however, highest during the dry seasons in Sahel Africa. Interannual changes in precipitation correlate with interannual changes in El Niño-Southern Oscillation (ENSO), while interdecadal changes in precipitation correlate with Pacific Decadal Oscillation (PDO). The objective of the study was to determine if there is spectral coherence of seasonal, interannual, and interdecadal changes in occurrence of meningococcal meningitis in Sahel, Central, and East Africa with interannual and interdecadal changes of PDO and ENSO. Time series were fitted to occurrence of meningococcal meningitis in Sahel, Central, and East Africa, to indices of precipitation anomalies in the Sahel, and to indices of ENSO and PDO anomalies. Morlet wavelet was used to transform the time series to frequency-time domain. Wavelet spectra and coherence analyses were performed. Occurrence of meningococcal meningitis showed seasonal, interannual, and interdecadal changes. The magnitude of occurrence was higher during warm climate regime, and strong El Niños. Spectra coherence of interannual and interdecadal changes of ENSO and PDO with occurrence of meningococcal meningitis in Sahel, Central, and East Africa were significant at p < 0.0001. Precipitation in Sahel was low during warm climate regimes. Spectra coherence of changes in precipitation in Sahel with ENSO was significant at p < 0.0001. ENSO and PDO are determinants of the seasonal, interannual, and interdecadal changes in occurrence of meningococcal meningitis. Public health management of epidemics of meningococcal meningitis should include forecast models of changes in ENSO to predict periods of low precipitation, which initiate occurrence.
Highlights
Meningococcal meningitis is a bacterial meningitis caused by Neisseria meningitidis, which is nonspore-forming, non-motile, gram-negative cocci
Meningococcal meningitis was first described in Europe in 1805, in USA in 1806, and in Sahel Africa in 1905, but several epidemics and pandemics occurred in the 19th and 20th centuries [6]
Indices of Pacific Decadal Oscillation (PDO), ENSO, and Sahel Precipitation Anomalies Multivariate El Niño-Southern Oscillation Index (MEI) data, which were computed from sea-level pressure, zonal and meridional components of the surface wind, sea surface temperature, surface air temperature, and total cloudiness fraction of the sky of the South Pacific Ocean [15] from 1950 to 2014 were downloaded from the website of National Oceanic and Atmospheric Administration1 (NOAA), USA, while intensities of El Niños from 1950 to present time were assessed using the Oceanic Niño Index (ONI) downloaded from http://ggweather.com/enso/oni. htm
Summary
Meningococcal meningitis is a bacterial meningitis caused by Neisseria meningitidis, which is nonspore-forming, non-motile, gram-negative cocci. Seasonal epidemics of meningococcal meningitis occur worldwide [4], but its burden of disease in Africa is estimated to exceed that of trypanosomiasis, Chagas disease, schistosomiasis, leishmaniasis, lymphatic filariasis, onchocerciasis, leprosy, and Climate meningococcal meningitis epidemics dengue combined [5]. Meningococcal meningitis was first described in Europe in 1805, in USA in 1806, and in Sahel Africa in 1905, but several epidemics and pandemics occurred in the 19th and 20th centuries [6]. In 1963, the meningitis belt was described in Sahel Africa [7], where most cases occur annually during the dry seasons. In addition to seasonal epidemics, cyclical epidemics occur every 8–12 in the Sahel [1], but the determinants are unknown
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