Spillover within Socioecological Systems

Our research aims to understand how socioecological processes shape risk and resilience in areas of high vulnerability to zoonotic spillover. Human contact with wildlife increases risk of exposure to wildlife origin zoonotic infections that can spillover into human populations, including hemorrhagic fever causing viruses (e.g. Ebola, Marburg, and Lassa). However, contact with potential reservoir hosts is often associated with risk trade-offs; for example conflicting infectious disease, nutritional, and social risks.  Contact with particularly “risky” prey (e.g. rodents, bats, and primates) varies across environmental and socioeconomic landscapes, further influencing the distribution of associated health risks and benefits among individuals, households, and communities. Spillover of pathogens from wildlife into human populations is thereby influenced by complex interactions within and among environmental and human components of integrated socio-environmental systems that may result in microhotspots of exposure and susceptibility to viral hemorrhagic fevers and other zoonotic infections.  Research in this area aims to identify entry points for One Health intervention strategies that prevent transmission and benefit human, animal, and environmental health.

Lassa Fever in Nigeria

Much of our research on this theme is currently focused on Lassa fever in Nigeria. Lassa fever is a rodent-borne viral hemorrhagic fever disease. It is a severe illness considered as an endemic and neglected tropical disease, with sporadic outbreaks that appear to be increasing in occurrence and spread across Nigeria. Lassa virus is responsible for an estimated 100,000-300,000 infections per year and approximately 5,000 deaths per year in West Africa (Guinea, Sierra Leone, Liberia, and Nigeria). These estimates are most likely to be under-reported in a context of a non-optimal access to healthcare and asymptomatic infections. After the 2013 Ebola outbreak shed light on other viral hemorrhagic fevers, Lassa has raised a growing concern in the international public health community. In 2018, Nigeria experienced an unprecedented outbreak, with an (under)-estimation of 1081 suspected cases and with 22% case fatality rate. The 2018 outbreak contributed to global concern of Lassa virus and generated confusion over the relative roles of increased awareness and diagnostic capacity versus socioecological changes in explaining the rise in Lassa fever cases. Nigeria continues to experience seasonal outbreaks of Lassa fever.

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Most of our knowledge of Lassa fever comes from Guinea and Sierra Leone, and there had been little research on epidemiology of Lassa fever in Nigeria.