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Could the avian flu be our next pandemic threat?

What does it mean that H5N1 bird flu, also known as highly pathogenic avian influenza A, is spreading among dairy cows? And how should U.S. health systems — and consumers of milk products — be responding?

The H5N1 bird flu, highly infectious and deadly in birds, has been around for nearly three decades, but recently, it has been changing in ways that raise alarms for many scientists and public health officials.

In particular, the recent spread of the virus among dairy cows and the discovery of genetic traces of the virus in 1 in 5 milk samples have sparked concerns that the virus may become more transmissible to humans. (No live virus strains of were found in the milk samples, and the Food and Drug Administration says pasteurized dairy products are safe to consume -- although raw milk and unpasteurized cheeses should be avoided.)

Michele Barry

While the public may be weary of pandemic news following four years of COVID-19, now is a critical time for scientists, public health officials and the general public to take preventive action, said Michele Barry, MD, director of the Stanford Center for Innovation in Global Health and senior associate dean of global health.

This includes taking steps to protect and monitor the health of livestock and the people who care for them through a "One Health approach" -- meaning one that fosters collaboration between countries, disciplines, and sectors to prevent disease outbreaks among humans and animals and protect their shared environments.

"This virus has the potential to seriously disrupt our agricultural supplies and also jump from other mammals to humans and become an epidemic or even a pandemic," Barry said.

This virus has the potential to seriously disrupt our agricultural supplies and also jump from other mammals to humans and become an epidemic or even a pandemic.

Michele Barry

Barry has responded to global pandemic threats ranging from the 2014 Ebola epidemic in West Africa to COVID-19, developed recommendations for how the CDC can strengthen its Global Migration and Quarantine division to prevent future pandemics, and advises on pandemic prevention as an elected member of the Global Health Advisory Board for the Council on Foreign Relations.

She discussed the response to H5N1, also known as highly pathogenic avian influenza A, and why recent developments should serve as a wake-up call to heighten surveillance by state and federal health officials, increase collaboration between farms and health officials, and improve international collaboration on pandemic prevention. This Q&A has been edited for length and clarity.

What do we know so far about the virus's impact on humans, and what should we be watching for?

We're aware of only one suspected transmission from a mammal to a human -- in a dairy worker this April. The case was mild and presented mainly as conjunctivitis. But birds can also transmit the virus to humans; since 1996, 868 cases have been recorded in humans -- of which more than half have been fatal. Most of the sick were infected on the job. While there's still much we don't know about the mortality rate in humans, these numbers are very concerning.

We have no current evidence of human-to-human transmission, but we also lack data. In the recent case of the infected dairy worker, researchers were unable to follow up or do serologic testing to understand how transmissible the virus might be to humans. The CDC must be invited in by states to conduct surveillance, and some agricultural officials and dairy farms have concerns about public health investigators gaining access to farms. To incentivize testing and surveillance, the federal government has offered up to $28,000 to livestock farms.

We need to closely monitor dairy and poultry farms, keeping an eye out for upticks in occupational illnesses and deaths, and ideally conducting blood tests among the animals and workers that can help us detect the virus in a population even if it is spreading asymptomatically.

We also need to closely monitor pig farms, because if this virus jumps to pigs, it could more easily mutate into an effective human-to-human transmitter.

Michele Barry

We also need to closely monitor pig farms, because if this virus jumps to pigs, it could more easily mutate into an effective human-to-human transmitter. Pigs are known as mixing vessels for influenza viruses because they can be infected by avian, swine and human influenza viruses. The genetic diversity of influenza viruses in pigs provides opportunities for the viruses to intermix genes and adapt to new hosts, including humans.

Are we any better prepared for bird flu than we were for COVID-19, should it become more transmissible in people?

In terms of treatments and vaccines, we are in a better position than we were at the beginning of COVID-19. Tamiflu, an antiviral medicine for treating the flu, appears to retain its effectiveness against this flu strain, and the U.S. has some stockpile of this medicine. We don't yet have a vaccine for this specific flu strain, but we do have vaccine candidates and a platform with which to build it.

However, it takes time to develop and scale up a vaccine. In a recent presentation to the Council on Foreign Relations, the CDC's deputy director, Nirav Shah, MD, acknowledged that there's a trade-off when it comes to developing an H5N1 vaccine. Doing so could pull resources from the development of the seasonal flu vaccine. In a regular year, the seasonal flu can hospitalize hundreds of thousands of people and kill tens of thousands -- so maintaining seasonal flu vaccination programs is critical.

Describe some key lessons learned in pandemic preparedness and prevention that you've helped surface through your work with the Council on Foreign Relations and the CDC. Are we heeding these lessons now?

We have learned many lessons in pandemic prevention from COVID-19, but I think many of them have been ignored. In terms of surveillance, communication, coordination and cooperation, we're not where we need to be.

We still have not changed our public health response by centralizing it. That's hindering the CDC's ability to go into states and conduct necessary surveillance on farms without being asked to come in.

Michele Barry

A key lesson learned from COVID-19 was the importance of a centralized response. In the U.S., we still have not changed our public health response by centralizing it. That's hindering the CDC's ability to go into states and conduct necessary surveillance on farms without being asked to come in.

It's very encouraging that the U.S. government has now committed to providing funding to livestock farms to support their preventive measures and testing for the virus, along with funding to support states that are restricting the movement of affected cattle. This may not be enough to really get our arms around this problem, but it's a promising start.

Another key lesson was the need for a surge fund to ensure that stocks of vaccine, personal protective equipment and medications can be scaled up quickly. These recommendations have not been implemented, nor has the U.S. increased sufficient funding to the CDC to deal with multiple pandemic threats at once.

Internationally, nations have yet to sign a pandemic accord meant to address the shortfalls in pandemic response that surfaced during COVID-19.

We need to educate farmworkers about the risks of exposure to the virus and how they can protect themselves.

Michele Barry

What can be done to minimize human exposure and improve surveillance among farmworkers, especially given that this population is often marginalized, faces language barriers and may not trust the government?

Perhaps most importantly, we need to educate farmworkers about the risks of exposure to the virus and how they can protect themselves. The federal government and local public health departments need to offer personal protective equipment such as N95 masks and gloves for farmworkers and teach them how to use it. We could also consider even more substantial financial incentives for dairy farms to participate in surveillance as well as ensure protection for undocumented workers involved in dairy farm work.

We can also protect farmworkers by mitigating the virus's spread in livestock. For instance, a vaccine exists for H5N1 in poultry and has been used, but it's not universal.

If we do face outbreaks on farms, Tamiflu, an antiviral, could be used prophylactically in settings with epidemic spread to help until a vaccine is developed. Of course, we always worry about antiviral resistance developing if Tamiflu is used indiscriminately.

While the current focus is on livestock, H5N1 has already caused widespread deaths in wild bird populations, infected at least 48 mammalian species and been described as "an ecological disaster." What can this impact on wild species tell us?

H5N1 has killed tens of thousands of marine mammals, including 24,000 sea lions in South America, and it threatens many other species. Yet such animal die-offs are often buried in the news -- to our detriment.

In West Africa, mass die-offs of gorillas and other mammals have been important harbingers of Ebola outbreaks in humans. H5N1 is a reminder of the very intimate connection between the health of wild animals, livestock and humans. Supporting healthy ecosystems is critical to preventing the next pandemic. 

Image: Emily Moskal

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Could the avian flu be our next pandemic threat?

What does it mean that H5N1 bird flu, also known as highly pathogenic avian influenza A, is spreading among dairy cows? And how should U.S. health systems — and consumers of milk products — be responding?