We learned on May 30 of a third human case of H5N1 infection, commonly known as bird flu, in the United States. This case was on a different farm than previous cases and presented with different symptoms.
Since March 29, there has been a major dairy cow outbreak with 86 infected herds across 11 U.S. states. Why have only three human cases been confirmed? Mainly because state and federal authorities have not actively or systematically looked for new cases of H5N1 infection in humans. Without a goal-oriented governmental response to the H5N1 outbreak — and a public health surveillance strategy that is aligned with these larger goals — the U.S. will not understand the true extent and implications of the outbreak, failing to protect its citizens and the rest of the world from a very real pandemic threat.
In public health (or epidemiological terms), a single case of H5N1 infection in a human constitutes an outbreak, since it is more than what would otherwise be expected. Any human outbreak of bird flu should be thoroughly investigated and tracked.
In order to address the outbreak properly, the government response must focus on several key areas.
First, it must vigilantly monitor and protect our food supply, including milk and beef, to prevent food-borne outbreaks and potential virus evolution. It should also involve preventing transmission from animals to humans and animals to animals by closely monitoring farm-associated spread, understanding risk factors, and characterizing the spectrum of illness in humans. Confirmed human cases that had direct contact with cattle demonstrate animal to human transmission is occurring and can result in respiratory symptoms.
However, it is also vital that we determine, with more specificity, how the virus transmits (including sources and routes of infection). We also need ongoing genomic surveillance of the virus’s characteristics and its evolution. This means we must systematically monitor the spread among cattle and other farm animals whether or not they show signs of illness. Local, state and federal government entities must then communicate this information with timeliness, intent and transparency. Effective communication can build trust before people are expected to take action.
Public health surveillance, the “ongoing and systematic collection, analysis, and interpretation of health data in the process of describing and monitoring a health event,” is a critical public health function that is essential for an effective outbreak response and control, and also for public information and warning. But surveillance strategies, like the governmental response, also need clear goals that can help set the parameters for response impact evaluation and next steps in response and communication.
What might the goals of public health surveillance look like for the current H5N1 situation? There are at least three key goals:
Identify early major sentinel events:
Sentinel surveillance is a strategy for the identification and tracking of important health events that need to be detected early. In the case of bird flu, important sentinel events include human infections, viral evolution or genetic reassortment of the virus, and the occurrence of person-to-person spread.
Current efforts to increase surveillance for human infections rely on farm workers to voluntarily submit to H5N1 testing, with the help of incentives. However, these incentives are likely not enough to support participation, given the potential professional ramifications for the workforce. H5N1-specific serologic testing in farm workers, which could determine the proportion that have ever been infected with H5N1, would be incredibly valuable right now. Existing cases were identified via monitoring of farm workers with a known exposure for the development illness for 10 days.
Understand and monitor the full scope of the animal and human H5N1 outbreaks:
The CDC, USDA Animal and Plant Health Inspection Service and FDA are monitoring H5N1 in human populations, animal populations and food products, respectively. But testing of animals and humans is not systematic and is often limited to animals with signs of illness. It is also unclear if these three data streams currently connect to one another. It is imperative to improve and collaboratively leverage these data streams by combining and triangulating them to better characterize and monitor the full scope of the outbreak and the threat it poses to public health, which includes the possibility of asymptomatic infection and transmission.
Track the spread of H5N1 into new populations and geographies and communicate the findings:
It is critical to track the spread of H5N1 across animal populations and human populations, and whether the food supply (including undercooked beef and raw milk products) is a concern for U.S. residents. The CDC’s National Wastewater Surveillance System (NWSS) collaborates with over 600 sites, with various partners. However, the NWSS cannot currently distinguish flu subtypes (such as seasonal flu versus H5N1) or the source (animal or human). We must deploy wastewater surveillance strategies that measure H5N1 directly, and differentiate H5N1 activity in humans from H5N1 activity in animals.
The U.S. H5N1 public health surveillance strategy must be designed to encourage state and local participation and inform public health agencies so that public health practitioners can make informed decisions under evolving conditions. Additionally, stakeholders and the lay public need quality communication about an emerging pathogen to avoid an information vacuum. Even well-designed, goal-driven surveillance systems can fail if they are not able to communicate actionable information to all those who need to know.
In the absence of a clear message indicating what U.S. government agencies know, do not know, are attempting to know, and are collaboratively doing to address the challenges, the information void will invariably be filled with alternative sources of information that may not be accurate nor evidence-based, putting us at the peril of our ignorance.
Dr. Rachael Piltch-Loeb is an assistant professor at the City University of New York (CUNY) Graduate School of Public Health in New York City and a senior fellow at the Harvard T.H. Chan School of Public Health with the Emergency Preparedness Research Evaluation and Practice Program.
Denis Nash, Ph.D., MPH, is a distinguished professor of epidemiology at the CUNY Graduate School of Public Health. He is also the executive director of the CUNY Institute for Implementation Science in Population Health and a former epidemic intelligence service officer with the Centers for Disease Control and Prevention.
Scott C. Ratzan, MD, MPA, MA, is founding editor of the Journal of Health Communication and distinguished lecturer at the CUNY Graduate School of Public Health and Health Policy. He co-chairs the Council for Quality Health Communication.
