The 2024 H5N1 (bird flu) outbreak in California has spread rapidly among poultry and dairy cattle, raising concerns about spillover into high-risk human populations, particularly farmworkers. Despite sporadic confirmed human cases, limited testing availability and participation have made it difficult to assess the true extent of infections.

This project will use antibody-based serological testing to evaluate H5N1 exposure in 300 high-risk poultry and dairy farmworkers across affected regions of California. Antibody testing can identify missed or asymptomatic infections and help trace possible transmission chains. Focus group discussions with farmworkers will explore their understanding of infection risks, workplace practices, and barriers to participation in public health surveillance.

Findings will inform culturally and linguistically tailored educational materials on infection prevention, protective equipment use, and workplace biosafety. The project also aims to support regulatory evaluation efforts by contributing real-world data to an ongoing Stanford Law School assessment of H5N1-related policies. The study is conducted in collaboration with the California Department of Public Health, United Farm Workers, and MesoScale Diagnostics.

“Issues of privacy and fear of punitive measures limited broad population testing. As a result, the true extent of H5N1 spread is unclear. Through our study, we hope to understand this better by testing workers for antibodies to the virus,” said Abraar Karan, Instructor in the Stanford Division of Infectious Diseases and Geographic Medicine, Department of Medicine

Principal Investigators:

Abraar Karan MD, MS, MPH, DTM&H; Instructor in the Stanford Division of Infectious Diseases and Geographic Medicine, Department of Medicine

Benjamin Pinsky MD, PhD, Professor; Stanford Department of Pathology

Research Team:

Stephen Felt DVM, MPH, DACLAM, DACVPM; Professor, Stanford Department of Comparative Medicine

Parastou Ghazi; Graduate Student, Stanford Woods Institute for the Environment

Juan Carlos Ruiz MS, MA; PhD Candidate, Department of Health, Society and Behavior, University of California Irvine

Deborah Ann Sivas, Director of the Environmental and Natural Resources Law and Policy Program, Stanford Law School

Gina Hervey, Sustainable and Humane Food Systems Legal Fellow, Stanford Law School

Sa Shen, PhD; Stanford Quantitative Sciences Unit

Funder:

Stanford Office of Community Engagement