Spatio-Temporal Factors Associated with Meningococcal Meningitis Annual Incidence at the Health Centre Level in Niger, 2004–2010

Abstract

BackgroundEpidemics of meningococcal meningitis (MM) recurrently strike the African Meningitis Belt. This study aimed at investigating factors, still poorly understood, that influence annual incidence of MM serogroup A, the main etiologic agent over 2004–2010, at a fine spatial scale in Niger.Methodology/Principal FindingsTo take into account data dependencies over space and time and control for unobserved confounding factors, we developed an explanatory Bayesian hierarchical model over 2004–2010 at the health centre catchment area (HCCA) level. The multivariate model revealed that both climatic and non-climatic factors were important for explaining spatio-temporal variations in incidence: mean relative humidity during November–June over the study region (posterior mean Incidence Rate Ratio (IRR) = 0.656, 95% Credible Interval (CI) 0.405–0.949) and occurrence of early rains in March in a HCCA (IRR = 0.353, 95% CI 0.239–0.502) were protective factors; a higher risk was associated with the percentage of neighbouring HCCAs having at least one MM A case during the same year (IRR = 2.365, 95% CI 2.078–2.695), the presence of a road crossing the HCCA (IRR = 1.743, 95% CI 1.173–2.474) and the occurrence of cases before 31 December in a HCCA (IRR = 6.801, 95% CI 4.004–10.910). At the study region level, higher annual incidence correlated with greater geographic spread and, to a lesser extent, with higher intensity of localized outbreaks.ConclusionsBased on these findings, we hypothesize that spatio-temporal variability of MM A incidence between years and HCCAs result from variations in the intensity or duration of the dry season climatic effects on disease risk, and is further impacted by factors of spatial contacts, representing facilitated pathogen transmission. Additional unexplained factors may contribute to the observed incidence patterns and should be further investigated.

A spatial and temporal analysis of paediatric central nervous system infections from 2005 to 2015 in Ho Chi Minh City, Vietnam

“…The significant association of both BI and non-BI incidence with concurrent or lags of temperature, rainfall and river water level suggests that climatic factors do play a critical role in the fluctuations of CNSI incidence. Climatic factors have also found to be associated with seasonality and temporal patterns of bacterial meningitis in Africa; dust in dry season could play a role in facilitating the entry of bacterial pathogens into the host [10,13]. We additionally observed a dramatic decrease in the incidence of BI associated with CNSI through time.…”

“…There is evidence to suggest that various spatial, climatic and socio-demographic risk factors may be associated with the incidence of CNSI in low-middle income countries such as those located in the African sub-Saharan meningitis belt and Asia (e.g. vector-born encephalitis is associated with proximity to rice cultivation and pig rearing and bacterial meningitis is associated with seasonality (the winter months) and high population densities) [10][11][12][13][14][15][16][17]. Vietnam faces continuing lack of access to costly vaccines against bacterial and viral etiologies of CNSI.…”

Cost-Effectiveness of Alternative Uses of Polyvalent Meningococcal Vaccines in Niger: An Agent-Based Transmission Modeling Study

“…Our ABM is a stochastic, and spatially-explicit model [34][35][36] to describe the meningococcal transmission across 44 districts of Niger (Figure 1 and Figure S2). Meningitis epidemics in Niger (along with other countries of meningitis belt) occur sporadically and, when they do occur, are of greatly varying severity ( Figure 2) [21,37,38]. This suggests that a stochastic model can best simulate the types of chance events that ultimately lead epidemic take-off or fade-out after the appearance of meningitis cases within a district.…”

The environmental drivers of bacterial meningitis epidemics in the Democratic Republic of Congo, central Africa

“…Many studies at different spatial scales and in different countries of the meningitis belt have been carried out, highlighting the role of dust, relative humidity and Harmattan winds in the different phases of meningitis epidemics [5,12,13,14]. The link between climate-environment and meningitis is becoming more and more evident through many scientific works and some environmental factors or proxies are also considered in early warning systems and prevention [5,15,16].…”