Compartmental models for seasonal hyperendemic bacterial meningitis in the African meningitis belt

Abstract

The pathophysiological mechanisms underlying the seasonal dynamic and epidemic occurrence of bacterial meningitis in the African meningitis belt remain unknown. Regular seasonality (seasonal hyperendemicity) is observed for both meningococcal and pneumococcal meningitis and understanding this is critical for better prevention and modelling. The two principal hypotheses for hyperendemicity during the dry season imply (1) an increased risk of invasive disease given asymptomatic carriage of meningococci and pneumococci; or (2) an increased transmission of these bacteria from carriers and ill individuals. In this study, we formulated three compartmental deterministic models of seasonal hyperendemicity, featuring one (model1-‘inv’ or model2-‘transm’), or a combination (model3-‘inv-transm’) of the two hypotheses. We parameterised the models based on current knowledge on meningococcal and pneumococcal biology and pathophysiology. We compared the three models' performance in reproducing weekly incidences of suspected cases of acute bacterial meningitis reported by health centres in Burkina Faso during 2004–2010, through the meningitis surveillance system. The three models performed well (coefficient of determination R2, 0.72, 0.86 and 0.87, respectively). Model2-‘transm’ and model3-‘inv-transm’ better captured the amplitude of the seasonal incidence. However, model2-‘transm’ required a higher constant invasion rate for a similar average baseline transmission rate. The results suggest that a combination of seasonal changes of the risk of invasive disease and carriage transmission is involved in the hyperendemic seasonality of bacterial meningitis in the African meningitis belt. Consequently, both interventions reducing the risk of nasopharyngeal invasion and the bacteria transmission, especially during the dry season are believed to be needed to limit the recurrent seasonality of bacterial meningitis in the meningitis belt.

Exploring the Need for Developing Impact-Based Forecasting in West Africa

“…Heat waves were identified as a major high impact weather event with significant impact on human health particularly in Nigeria and Senegal. Participants stated that heat waves frequently lead to outbreak of deadly diseases such as meningitis which is in line with what has been reported in other studies in the region (Agier et al, 2013;Koutangni et al, 2019). Heat waves have been reported to have significant impact on mortality and morbidity in Africa with the urban heat island effect increasing the health risk for people living in cities (Zaitchik, 2017).…”

Perfil da meningite na população pediátrica no estado de Minas Gerais, Brasil

“…Duas principais hipóteses têm sido levantadas para explicar essa relação. A primeira, sugere que as condições climáticas observadas nos meses mais secos de inverno poderiam ocasionar danos à nasofaringe, facilitando a invasão de certos patógenos, enquanto a segunda se relaciona com um maior aumento da transmissão bacteriana, promovido por fatores ambientais ou comportamentais [23]. Todavia, o presente estudo observou que o pico de notificações na faixa etária pediátrica em MG se deu no mês de dezembro, ou seja, em um período chuvoso, típico do verão e contrário ao que se esperaria para o restante do território brasileiro, onde o número de casos se acentua no outono e inverno [22].…”

A spatiotemporal model of meningococcal meningitis with direct and indirect transmission

“…The first suspicion of climate largely impacting meningococcal meningitis transmission dynamics was inspired by the finding that the seasonal profile for meningitis coincided with the core of the dry season, when the Harmattan regime is well settled, and ended with the coming of the African monsoon 12,38–40 . Meningococcal and pneumococcal meningitis incidence displays a seasonal pattern during the dry season (December through May) with a 10‐ to 100‐fold increase of weekly incidences at local health center, district, and national levels, which subsides with the onset of the rainy season 40–43 . Bacteria are found in the dust and sand winds brought by the Harmattan (dry season) out the protective mucosal barrier, weakening the immune defenses and facilitating the spread of the disease.…”

“…Though our mathematical model is accurate to predict meningococcal meningitis transmission dynamics, it could be improved by considering the wind direction during the Harmattan. For that, we have included the convection in model and the seasonality spread of the disease that usually occurs during the dry period 42 …”