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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Effective surveillance in areas most prone to outbreaks would facilitate earlier diagnosis, increase survivors, reduce nosocomial infections, and allow intervention/prevention strategies. In response to this challenge, we joined the University of Cambridge's Sentinel Team in response to design and implement the the Sentinel outbreak surveillance platform linking epidemiological surveys and laboratory immunology samples with GPS and body temperature data, displayed in real-time. 

Why the social sciences and anthropology should complement the epidemiological insight


Anthropology is increasingly recognized as an important part of epidemic response, integrating local health knowledge and belief systems into effective health policy strategies. For example, during the 2013 Ebola outbreak the incorporation of social scientists and anthropologists into a combined public health effort dramatically helped improve outcomes. The role of anthropology in preventing outbreaks has been comparatively under realized. Anthropological research can also help us understand human ecological relationships with reservoir species that predispose spillover and human social relations that enable secondary transmission within communities. The following sites provide an in-depth overview of the role of anthropology and social sciences in Ebola Virus Disease and Lassa Fever.

Human-Rodent Interactions and the Ecology of Lassa Risk


Lassa virus is transmitted to humans via contact with rodents and their bodily fluids. However, limited information exists on human-rodent interactions within Nigeria and the risk factors for Lassa virus transmission generally.  This has severely limited our ability to communicate risks and establish effective prevention strategies across the vast socioecological contexts in which Lassa exists.  Through a mixed methods case control study, our ongoing research offers uniquely comparative and in-depth analysis of behavioral risk factors for community transmission of Lassa.  We hope results from our ongoing research will help identify risk factors for Lassa virus infection and thus entry points for evidence based and culturally appropriate risk communication and intervention. Led by Sagan Friant In collaboration with OVEL.

Perceived risks and treatment seeking

Lassa epidemiology and control is severely limited by heterogeneity in availability of and access to diagnostic and treatment facilities. Barriers exist within communities and health systems that together shape health seeking behavior and health care. Understanding local perceptions of health risks and their socioecological context is necessary to inform effective and sustainable health policies and build robust health systems. Through qualitatively driven mixed methods research, we aim to understand how local knowledge of Lassa and concepts of illness shape health seeking behavior and health care, as well as how these interactions are modified by structural barriers limiting access to diagnostic and treatment facilities within a Lassa endemic region of Nigeria. Results will help improve the access to health care and health system strengthening. Led by Métrey Tiv in collaboration with OVEL.