Emerging and recurring disease outbreaks, for example the recent outbreaks of COVID-19 and the seasonal patterns of cholera, highlight the urgent need to improve public health responses worldwide. Now, an interdisciplinary team from Penn State has been awarded $2.3M from the National Institutes of Health and the National Science Foundation’s joint Ecology and Evolution of Infectious Disease (EEID) program to evaluate the vulnerability of certain populations to disease outbreaks, with the goal of improving outbreak response and preventing future outbreaks.
The team is led by Nita Bharti, assistant professor of biology, faculty in the Center for Infectious Disease Dynamics, and Lloyd Huck Early Career professor, and includes Anthony Robinson, associate professor of geography, director of online geospatial education programs, and co-director of the GeoGraphics lab. Their work will specifically analyze the factors underlying measles and Ebola outbreaks in the Équateur province of the Democratic Republic of Congo. The methods and tools the team develops will also be valuable to assessing vulnerability to a variety of disease outbreaks in other areas of the world.
“We’re studying measles and Ebola to understand the processes that underlie pathogen transmission across a range of infectiousness and prevalence,” said Bharti. “We want to identify the important characteristics of populations and environments that increase vulnerability to diseases as well as how and why those factors are different for different diseases.”
Measles, much like polio and other “endemic” diseases, could be on the edge of elimination, thanks to vaccines and other intervention efforts, but instead continues to circulate and cause outbreaks. By contrast, Ebola is an “emergent” disease that is caused by spillover events—when a pathogen jumps from another animal host species to humans and then transmits between humans, like monkeypox.
“Ebola has spilled over multiple times since it was first identified in 1976 and continues to spill over from wildlife to humans,” said Bharti. “The Équateur province in the DRC experienced a rare Ebola spillover event in 2018, another in 2020, and yet another in 2022. This increasing frequency indicates that changes in the region are facilitating spillover events, for example how and when humans interact with host species. This is important to investigate because it can help us understand contributors to spillover events more broadly.”
In addition to these Ebola spillover events, the DRC also experiences recurrent measles outbreaks, including a very large one in 2019. The region therefore provides an opportunity for the researchers to explore how factors that increase vulnerabilities in populations might differ across a range of disease dynamics—endemic to emerging—and how those factors influence outbreak preparedness and response.
The team will first explore how people are moving and interacting within the region in order to define spaces that are relevant to epidemiology —the study of disease spread and treatment—and how they change over time. This is in contrast to many current prevention and intervention strategies that are based on administrative units, which often follow political boundaries. But, according to Bharti, these boundaries aren’t always reflective of how people move or how populations interact and transmit pathogens.
“These boundaries also don’t reflect how people intersect with geography," added Robinson. “For example people might regularly interact with each other across an ‘official’ boundary, but not interact as often across a major river or mountain range within that boundary.”
“Our first goal is to understand how people are moving and interacting to transmit pathogens and establish what we call ‘epidemiological units,’” Bharti said. “We can plan more efficient preventive or reactive outbreak management by targeting a population that is at risk of disease transmission due to their interactions.”
The researchers will also explore how interactions, and thus the epidemiological units, change over time, for example seasonally or as populations grow in an area. This aspect of the project will include considerable efforts to create and update maps for the province and other ways to visualize information for a field team.
“We’ll be working with field teams to understand their approaches to outbreak response and to design mapping solutions that reflect their specific needs, rather than expecting them to continue to rely on maps and spatial analysis tools that are built for generic purposes,” said Robinson. “We need to understand the intricacies of data analysis and policy work by the people who are on the front lines of response efforts and to shape new geographic information sources that speak directly to those needs.”
The team will integrate information about population movements with traditional measures of vulnerability, such as income and access to medical resources. Then, they will use disease modeling to explore how different intervention strategies might play out based on the identified epidemiological units, targeting where key interactions occur.
“The current system of outbreak response reacts to thresholds of cases per capita and is conducted within administrative boundaries. We’re going to evaluate strategies that also target movement and interactions of populations,” said Bharti. “We’ll compare and integrate these strategies and improve upon them to produce the most favorable outcomes.”
Much of the information and maps will be promptly applicable to people working in the Équateur province, such as groups like Doctors Without Borders and the Ministry of Health in the DRC, with whom the researchers work. Additionally, the work provides a case study for how to identify factors that are important for epidemiological vulnerability for both endemic and emerging diseases and how to include these factors in real disease scenarios and humanitarian outreach.
“Once you understand what's driving vulnerability, you can start to develop strategies to address it,” said Bharti. “Every population contains socially constructed vulnerabilities, which are the result of social factors, such as access to housing, nutrition, and health care, that create differences in health and disease outcomes. Identifying and incorporating the critical aspects of these social factors into infectious disease management and prevention is one of the goals of this project. If we continue to proceed as if there are just unfortunate populations and places that are continually hit harder than others by disease outbreaks, then we will continue to ignore the causes of health inequities. By combining concepts from biology, geography, and anthropology, we hope to help identify some of the origins of these health inequities and tailor strategies to target them.”