Last week, the CDC reported the first patient death from H5N1 in the US. Astrian Horsburgh, a former CDC public health advisor in disaster preparedness, offers a summary of what the experts are saying about H5N1 and what you can do to protect yourself.
As we begin 2025, influenza H5N1 is among the biggest public health threats the world faces today. 2024 saw H5N1– also known as “bird flu” or highly pathogenic avian influenza (HPAI) – jump to cattle for the first time, and spread like wildfire through dairy herds. Over 900 outbreaks in poultry and cattle have been detected nationwide, and the virus has spread among many other species as well, with particular lethality in cats. 66 cases in humans have been reported in the US so far. With the first human death due to H5N1 in Louisiana last week, alarm bells should be ringing loud and clear.
A recent RAND Corporation report put this concern in strong terms: “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.” While over $2 billion have been spent to reimburse farms for their losses and to develop and stockpile vaccines, crucial efforts toward disease surveillance, testing, and information sharing have been slow, inconsistent, and opaque. RAND’s report issues a sobering warning about the lethargy and confusion hampering the H5N1 response so far, and points to parallels with the COVID-19 response that was characterized by confusion, contradiction, and panic.
Under the right conditions, H5N1 could be far worse than COVID. Kaiser Family Foundation reports that “Over the past 30 years, half of around 900 people diagnosed with bird flu around the world have died. Even if the case fatality rate is much lower for this strain of the bird flu, COVID-19 showed how devastating a 1% death rate can be when a virus spreads easily.” While H5N1 typically only spreads between infected animals, and from animals to people, there is evidence from past outbreaks that human-to-human transmission is a genuine risk.
Even considering only the cases caused by transmission from animals to humans, H5N1 should be cause for alarm. So far, most reported cases have not required hospitalization, but the symptoms – like painful conjunctivitis – may be very unpleasant. Poultry and dairy farm workers are most at risk right now because of their close proximity to infected animals. Cases among farmworkers are almost certainly underreported, and many livestock workers have not even been warned about the risks they face, much less provided with testing or the ability to stay home when sick.
The smoking gun that would elevate this virus to catastrophic levels would be clear evidence of human-to-human transmission. In the words of Dr. Andrew Pekosz, professor of Molecular Microbiology and Immunology at Johns Hopkins, “If we start to detect people with H5N1 whose only contact was another person infected with H5N1—that would be a real danger sign.” So far this has not been definitively detected, but each infection runs the risk of mutations which could permit human transmission.
It is also not reassuring that, while most patients have become infected through contact with infected animals or wild birds, at least three cases (two in the US and one in Canada) have no known source for their illness. One of those patients, who was hospitalized in Missouri for H5N1, was later found to have potentially transmitted the virus to seven contacts – one household member and six healthcare workers – who also developed respiratory illnesses. Because none of them were tested at the time, person-to-person transmission cannot be confirmed, but the possibility is there, and worrisome. If not a perfect smoking gun yet, this certainly looks like smoke.
One particularly dangerous scenario would be someone – potentially a farmworker, though not necessarily – contracting both H5N1 and regular influenza simultaneously, risking a “reassortment event,” in which genetic material from multiple viruses combines and results in a new virus that can spread person-to-person. Back in July 2024, experts recommended getting a jump on both spreading awareness and preparing for vaccine distribution ahead of the flu season, but we’re now entering 2025 with the public only dimly aware of the threat of H5N1, and farmworkers – the most affected population – still inadequately informed and poorly protected.
Meanwhile, mutations are occurring – if not to enable human-to-human transmission, at least to potentially increase disease severity. The CDC says a Louisiana patient who contracted the country’s first severe case of H5N1 also showed signs of mutations in the virus that allowed it to bind better to human receptors. This patient was also the first human death from H5N1, as of early January 2025. Meanwhile, a Canadian teenager, whose illness was both unrelated to animal contact and severe enough for her to require a prolonged stay in the intensive care unit, also shows various mutations. It is unclear if the mutations detected in her strain of H5N1 developed during her illness or were already present when she got sick. However, it is confirmed that the severe Canadian case and the severe Louisiana case were both caused by a strain of H5N1 called D1.1, while the strain responsible for the majority of US cases is B3.13. Even if the virus has not yet been shown to spread rapidly person-to-person, the evolution of a strain associated with more severe illness and even death is cause for concern.
If the virus could have been contained on the Texas farms where it was first detected in cows, we would be facing a very different threat landscape today. But that ship has sailed. H5N1 has been devastating to the poultry industry, destabilizing for the dairy industry, and an ongoing health risk to unprotected farm workers. What it will mean for the rest of us remains to be seen. If this brewing storm sounds familiar, it should. We have all seen how quickly and aggressively a virus can spiral out of control.
One advantage this time around is that bird flu is, at least, a familiar virus. The Center for the Biomedical Advanced Research and Development Authority (BARDA) already has a stockpile of a vaccine against bird flu, although it is experimental and not yet approved. This vaccine could be put into use through an Emergency Use Authorization if H5N1 were to escalate into a pandemic, but otherwise it would still require testing in mass clinical trials first. Vaccines for poultry, swine, and cattle also exist or are in development, although there have been roadblocks to their approval and distribution.
A clear-headed and safety-centered response must include practices such as increased transparency and data sharing, robust surveillance, testing, and monitoring (of dairy herds, food products, and farmworkers), and distribution of vaccines when available, for both livestock, agricultural workers and eventually for other populations at risk. Local and federal communication and collaboration has also been characterized thus far by obstruction, obfuscation, and secrecy, which is its own health hazard. Public health officials, farmworkers, the public itself, and international partners – many of whom are dismayed at the US’s fumbling response thus far – deserve clear and accurate information as this threat progresses.
For people who are further removed from the vectors of the virus in everyday life, vigilance is paramount for now. Don’t touch wild animals, especially birds. Keep your cats indoors, and avoid feeding them raw pet food or raw milk. While uncommon, it is possible for the bird flu virus to spread from your pets to you–and vice versa. Monitor your pets for signs of illness, and monitor yourself as well. Symptoms are generally similar to those of the common cold (fever, nasal congestion, cough); less commonly, infection can also present with GI symptoms like nausea, vomiting and diarrhea. Many patients also report conjunctivitis, which can be severe.
How to Prevent H5N1 Infection
According to CDC, you should cook your poultry, meat and eggs thoroughly, and avoid unpasteurized milk or other dairy products, because unlike COVID-19, this virus can invade not only via the respiratory route but the gastrointestinal tract too. Get a flu shot – you don’t want to be the person who develops both regular flu and bird flu, and gives the virus a chance to mutate catastrophically. And if and when this virus starts to spread widely–then, as for any infectious disease, we will need to remember the personal protective measures we practiced with COVID: avoid crowded public spaces, wear masks (KN95 or better) when contact with others is unavoidable, test if you experience symptoms or are exposed (once there are rapid tests available for H5N1), isolate if sick, and get vaccinated with a specific H5N1 vaccine when it’s possible and recommended.
Will we really have to do all this again? Too soon to say. But it’s better to be prepared now than sorry later.
–by Astrian Horsburgh, Health Equity Institute intern and former CDC public health advisor at the Oklahoma City-County Health Department.
Photo credit: Madison Oren, Unsplash.com
Medical disclaimer:
The suggestions given here are not intended as a substitute for the medical advice of your physician. The reader should regularly consult a physician in matters relating to his/her health and particularly with respect to any symptoms that may require diagnosis or medical attention. For additional questions, please call your healthcare provider for reliable, up-to-date information on testing and symptom management of all medical concerns.
