Quantifying Poverty as a Driver of Ebola Transmission

Abstract

Background: Poverty has been implicated as a challenge in the control of the current Ebola outbreak in West Africa. Although disparities between affected countries have been appreciated, disparities within West African countries have not been investigated as drivers of Ebola transmission. To quantify the role that poverty plays in the transmission of Ebola, we analyzed heterogeneity of Ebola incidence and transmission factors among over 300 communities, categorized by socioeconomic status (SES), within Montserrado County, Liberia. Methodology/Principal Findings: We evaluated 4,437 Ebola cases reported between February 28, 2014 and December 1, 2014 for Montserrado County to determine SES-stratified temporal trends and drivers of Ebola transmission. A dataset including dates of symptom onset, hospitalization, and death, and specified community of residence was used to stratify cases into high, middle and low SES. Additionally, information about 9,129 contacts was provided for a subset of 1,585 traced individuals. To evaluate transmission within and across socioeconomic subpopulations, as well as over the trajectory of the outbreak, we analyzed these data with a time-dependent stochastic model. Cases in the most impoverished communities reported three more contacts on average than cases in high SES communities (p<0.001). Our transmission model shows that infected individuals from middle and low SES communities were associated with 1.5 (95% CI: 1.4–1.6) and 3.5 (95% CI: 3.1–3.9) times as many secondary cases as those from high SES communities, respectively. Furthermore, most of the spread of Ebola across Montserrado County originated from areas of lower SES. Conclusions/Significance: Individuals from areas of poverty were associated with high rates of transmission and spread of Ebola to other regions. Thus, Ebola could most effectively be prevented or contained if disease interventions were targeted to areas of extreme poverty and funding was dedicated to development projects that meet basic needs. Author Summary: Despite recognition that resource constraints contributed to the difficulty in controlling West Africa’s ongoing Ebola outbreak, no previous study has been conducted to quantify the impact of poverty on transmission. In particular, the extent to which within country heterogeneity in socioeconomic status (SES) could be driving geographic spread or sustaining Ebola hotspots has important implications for control policies. In Liberia’s capital city Monrovia, approximately 68% of the population occupies slum neighborhoods characterized by overcrowding and lacking sanitation—conditions conducive to outbreaks of infectious disease. The researchers find that infected individuals residing in these most impoverished settings are associated with three times more Ebola transmission, as well as greater dissemination of disease between communities of different socioeconomic levels. Cases from low and middle SES areas reported significantly more contacts during their symptomatic and therefore infectious periods than cases from high SES areas. Overcrowding and lack of education on how the disease is transmitted could explain the observed differences in number of secondary cases. The findings support the need for targeted response measures that account for differential risk arising from socioeconomic heterogeneity within West African countries.

Publication information

Originally published in PLOS Neglected Tropical Diseases on 2015-12-31. Original DOI: 10.1371/journal.pntd.0004260.

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