His research focuses on epidemiology and risk assessment of foodborne and zoonotic diseases and their prevention in the USA and globally. He has published extensively on the global burden of foodborne disease, including in his role as chair of the WHO Foodborne Disease Burden Epidemiology Reference Group. He contributes to the Feed the Future Innovation Lab for Livestock Systems, leads the "Campylobacter Genetics and Environmental Enteric Dysfunction (CAGED)" project and participates in several other projects focusing on food safety and zoonotic infections in low- and middle-income countries. His current research is funded by the Bill & Melinda Gates Foundation, the United States Department for International Development, the UK Department for International Development and the Florida Department of Health.