The United States is failing to act decisively against the growing H5N1 threat, with human cases already emerging from unknown origins and evidence of widespread animal transmission. Without immediate nationwide livestock testing and isolation, expanded wastewater surveillance, and rapid vaccine distribution to at-risk populations, the virus risks mutating into a form capable of sustained human transmission—repeating the catastrophic delays of COVID-19. With the news of the first severe H5N1 case requiring hospitalization in Louisiana, concern for U.S. response has escalated. California Governor Gavin Newsom declared a state of emergency on December 18th, in response to more than 300 herds testing positive in the last month. Time is running out to contain this threat before it spirals out of control.
On January 31st, 2020, the COVID-19 pandemic crossed a procedurally important threshold when it was declared a Public Health Emergency of International Concern (PHEIC) by the World Health Organization (WHO), and a Public Health Emergency (PHE) by the Secretary of the Department of Health and Human Services. These declarations triggered critical international and national mechanisms, enabling the allocation of emergency funding, the mobilization of resources, and the coordination of a global response to the emerging threat. Despite these declarations, the speed of government response was consistently behind that of disease transmission, highlighting a trend prominent throughout the pandemic. Despite these lessons, the ongoing H5N1 outbreak among U.S. dairy farms is proving to be a painful indicator of ever-present failures in response, coordination, and prioritization.
As of December 18th, 61 human cases of HPAI (A)H5N1 (Highly Pathogenic Avian Influenza, or bird flu) have been confirmed in the United States. Two of these cases are of unknown origin. Although primarily a virus of birds, H5N1 is a zoonotic disease with a wide host range that can infect humans and other animals. Currently, the virus is mostly spreading in chickens and dairy cows, although there have been reported infections in cats, dogs, goats, and a variety of wild animals. Recently, an H5N1-infected pig raised significant concern due to the unique role pigs can play in influenza virus evolution. As hosts capable of being infected by multiple influenza virus subtypes, pigs provide an environment for a viruses' genetic reassortment. Recombination of genetic material from different viral strains can potentially lead to the emergence of novel and more transmissible variants, meaning that completely new influenza viruses can emerge from pigs with the ability to infect new host species with little or no preexisting immunity to the virus. The 2009 H1N1 swine flu pandemic is thought to have started from multiple reassortment events in pigs before spilling over to humans.
The ongoing H5N1 outbreak among U.S. dairy farms is proving to be a painful indicator of ever-present failures in response, coordination, and prioritization.
While the current strain of H5N1 is not considered to be contagious enough among humans to allow for sustained human-to-human transmission, recent cases have begun to call this into question. One teenager in Canada, for example, contracted H5N1 with no known animal contact, and has been in the ICU for several weeks. Another case in Missouri could not be linked to any animal exposure, either. These are worrying signs that the virus has the potential to cause significant morbidity, and that human-to-human transmission in currently circulating strains is possible. Coupled with a slow response and challenges in scaling up testing, there is growing concern that the outbreak could easily and rapidly spread beyond control.
Failing to act decisively risks repeating the missteps of early COVID-19 response efforts, where hesitation and underestimation allowed opportunities for containment to slip away. Building on heightened awareness and the lessons of recent history, we present three recommendations that, if enacted, can curtail H5N1 transmission, enhance preparedness for a potential human epidemic, and foster trust within the scientific and public health communities.
Recommendation 1: Declare H5N1 a PHE and mandate ongoing nationwide testing of representative samples of dairy and beef cattle, free of charge to farmers. Implement increased testing of farm and dairy workers, livestock vaccinations, and indemnity payments.
PHE declarations play a critical role in unlocking funds for surveillance, testing, research, health care reimbursement, and staffing for disease mitigation and containment. Notably, PHE declarations are not unprecedented or unduly alarming, as they are currently in place for the opioid crisis and recent hurricane responses in southern states. The U.S. Department of Agriculture (USDA) and Animal and Plant Inspection Service (APHIS) must fully utilize their authority under the Animal Health Protection Act (AHPA) and coordinate with the Centers for Disease Control and Prevention (CDC) to expand mandatory testing to all cattle populations and provide resources for testing farmworkers.
Testing milk and cattle from states without identified cases or outbreaks should be a key part of the U.S. national biosurveillance strategy and H5N1 response. The USDA has recently announced a plan to test milk nationwide, but there is no mandate to test either farm workers or even the dairy cows themselves if they are not shipped across state lines. Under the AHPA, the USDA has the authority to implement measures, such as testing and isolation of cattle to prevent the introduction and spread of infectious diseases in livestock. There is also no reason to suspect that the virus uniquely affects dairy cattle and not beef cattle, but the reliance on voluntary testing of milk samples leaves beef cattle largely untested—even though the animals themselves are immunologically indistinguishable from dairy cattle.
While the USDA and APHIS are understandably focused on ensuring the safety of the U.S. milk supply, which impacts far more individuals than direct interactions with cattle, this approach overlooks an important risk. Dairy workers, farmworkers, and others in close contact with livestock face immediate and ongoing exposure, and without containment and treatment efforts targeting infected animals, the virus will continue to circulate and mutate. Viral mutations are very worrying for the prospect of future human spread. A recent study found that a single amino acid mutation allows H5N1 to bind human hemagglutinin (HA) receptors, readily enabling human infection and human-to-human spread. Expanding testing beyond the milk supply and interstate shipments of dairy cattle will increase our knowledge of the outbreak and guide efforts to protect those most at risk.
Testing is one piece of the response, and while it is a critical tool to identify cases, it should be done in conjunction with preventative measures that address risk further upstream. In addition to isolating and treating infected animals, vaccination of susceptible dairy cows must be significantly expanded. Currently, two USDA field trials are ongoing to evaluate the safety of bovine vaccine candidates, but no vaccine has been widely implemented. This leaves the bulk of U.S. dairy herds susceptible to infection, increasing the chances that H5N1 will continue to spread and mutate. While the USDA is currently investing heavily in vaccine testing, a comprehensive distribution plan should be developed and published imminently to ensure widespread vaccination occurs quickly after approval.
Lastly, compensation and financial support for impacted farms is vital to ensure compliance to outbreak response, but also to protect the industry. Similar to financial protection for impacted poultry farms when culling is necessary due to H5N1, the same level of protection is needed for farmers who are experiencing loss of milk production. While infected cows tend to recover well, milk production can be dramatically reduced. The USDA is working to offset this. The agency noted in May 2024 that it “anticipates that its forthcoming rule will specify that farmers will receive payments at 90 percent of lost production per cow, for a set period of time retroactive to the date of the confirmation of their positive herd status, starting with the first herd that tested positive in March 2024.” Ensuring financial protection for farms should also expand to those workers reporting symptoms and undergoing testing or isolation. Preventing human spillover and transmission is critical to limit potential virus genetic changes that could allow for sustained transmission.
Recommendation 2: Expand CDC's National Wastewater Surveillance program to test for H5N1 and associated variants from different hosts.
In response to the COVID-19 pandemic, the CDC began the National Wastewater Surveillance program—tracking levels of SARS-CoV-2 in wastewater samples collected nationwide. Since then, the program has expanded its partnerships and integrated surveillance of influenza, mpox, respiratory syncytial virus (RSV), and now H5N1. H5N1 has been detected in wastewater in at least ten U.S. states, and has been directly detected in birds or animals in every state, strongly implying that transmission extends beyond infected dairy herds. However, wastewater testing for H5N1 has difficulty discriminating between virus shed by animals, by humans, or from discarded dairy products.
While the CDC program tracks four viruses, the philanthropically funded WastewaterScan program tracks 13 viruses and one fungus at municipal wastewater treatment plants that serve over 10,000 people. Wastewater testing has the potential to provide early and widespread indications of H5N1 community spread, if reliable genetic markers for the virus can be identified. During the COVID-19 pandemic, wastewater surveillance enabled health officials to detect emerging outbreaks and variants, helping to inform public health measures such as travel advisories, resource allocation, and health care preparedness.
Funding for biosurveillance programs such as wastewater surveillance should not be unique to public health emergencies or specific outbreaks, but rather a sustainable part of pandemic prevention and global health security. This “One Health” approach emphasizes the interconnectedness of human, animal, and environmental health, which requires ongoing prevention, identification, response, and resilience efforts—one of which is biosurveillance.
Funding for biosurveillance programs such as wastewater surveillance should not be unique to public health emergencies or specific outbreaks, but rather a sustainable part of pandemic prevention and global health security.
Recommendation 3: Make H5N1 vaccines available to anyone likely to have been exposed to infected animals, and prepare a plan for nationwide distribution.
In addition to expanding testing and focusing on prevention in animals, the United States needs to scale up deployment and distribution of the H5N1 vaccine. Unlike the COVID-19 pandemic, where a vaccine was developed during the PHEIC, a vaccine that is effective against the most common strain of H5N1 is available in the Strategic National Stockpile. Should a broader outbreak occur, this vaccine is capable of being produced at quantities sufficient to vaccinate the U.S. population. The stockpile currently contains between 19 and 457 million bulk vaccine and adjuvant doses, depending on the actual dosage required. The Administration for Strategic Preparedness and Response (ASPR) is providing $72 million to vaccine manufacturers to increase production capabilities and produce individually dosed vaccine (including preparing currently stockpiled bulk dosages for individual dissemination).
But the question remains: When is it best to distribute doses to farmworkers, dairy workers, or other individuals in close contact with animals, or the general population? Increasing concerns regarding viral reassortment and missed cases during the 2024–2025 seasonal flu season should prompt a rapid distribution of this available vaccine now. COVID-19 provided several valuable lessons on vaccine rollout and the palatability of vaccines to the general public, indicating that early and frequent communication about vaccines, as well as the availability (without formal requirement) of multiple forms of a vaccine, may increase uptake without stressing the ability of the health care and pharmacy system to deliver vaccines rapidly.
In conclusion, the ongoing H5N1 outbreak presents a critical test of the United States' ability to apply the hard-earned lessons of all too recent health emergencies like the COVID-19 pandemic and mpox outbreak. Mandating testing and isolation of at-risk livestock, expanding wastewater surveillance, ensuring protection for farms, and increasing vaccine availability are urgent steps to contain the virus, prevent further zoonotic spillover, and prepare for potential human-to-human transmission. By acting decisively now, we can reduce the risk of further disease transmission, safeguard public health, and reinforce the resilience of our national and global security infrastructure. The time to act is not when the threat becomes unmanageable—it is now, when swift, coordinated efforts can make the greatest impact.
