Episode 21: Updates on Avian Influenza H5N1 with Lizzie Wilson

The Public Health Report

Hi! Welcome to episode 21 of the Public Health Report, where we discuss current events in the public health sphere. I’m your host this week, Lizzie Wilson, and today we’re diving into the emerging public health threat that’s making a lot of headlines lately, and that is avian influenza H5N1.

On Wednesday, February 8th, the director of the World Health Organization made an announcement concerning H5N1 in minks, otters, and sea lions. Now, typically these avian influenza A viruses affect aquatic birds, but sometimes they also affect poultry and other animals as we see here.

You may have heard about the outbreak of H5N1 at a mink farm in Spain. It occurred in October and was reported on in Eurosurveillance on January 19th[i].

Here’s what happened: At the beginning of October 2022, mink farm workers noticed that the animal’s mortality rate jumped from 0.25% up to 0.77%. At this point, they began testing the animals for viruses, including H5N1 and SARS-CoV-2, and found that they tested positive for H5N1. The disease appeared to spread in hotspots around several pens, leading many minks to become infected with H5N1, and ultimately all 51,986 animals were culled. However, despite coming into contact with infected minks, no farm workers tested positive for the virus.

A news article published in Nature last week explains why this particular outbreak is concerning[ii]. Unlike in past outbreaks of H5N1, this one demonstrates mammal-to-mammal infection. Previously, all infections in mammals could be attributed to contact with materials contaminated with the virus, such as bird droppings or infected feed. But in this case, poultry farms supplying feed to the mink farm did not experience outbreaks of H5N1, and it is likely that infected wild birds—attracted by the mink’s food— entered these high-density open air cages were minks are kept, and the virus eventually jumped species and then spread amongst minks[iii].

Currently, H5N1 is not efficiently and sustainably transmitted between humans. And that bears repeating: The current threat to human health is low. In fact, the New York Times reports that globally only 10 cases of H5N1 have been reported in humans since December of 2021—notably with 0 reported cases of human-to-human transmissioniii. However, in cases of human infection of H5N1, WHO reports a 56% case fatality rate[iv].

There are some warning signs that could make human-to-human transmission (and a pandemic) more likely. Let’s briefly touch on those:

· So first, H5N1 is infecting a larger number of migratory birds, which raises the risk of a new variant spreading to people.

· Second, H5N1 infected minks, and likely spread mammal-to-mammal in October. This is unprecedented, and it’s especially alarming because the upper respiratory tract of minks is a very good conduit for humans[v].

· Third, if a farmer infected with a different strain of influenza were simultaneously infected with H5N1, these viruses could undergo reassortment–a process of swapping genes during co-infection—and potentially create a virus that is more transmissible between people[vi]. Indeed, a 2021 study in Emerging Microbes and Infections found that minks are commonly infected with both human and avian influenza A viruses, making them an ideal species for reassorting these viruses—and these researchers recommend taking steps to minimize contact with raw poultry products as well as taking urgent steps to increase surveillance at mink farms[vii].

Right now, most people affected by H5N1 notice it at the grocery store—in the form of egg shortages and rising food costs. And even without infecting people this is serious—since the start of 2022, the CDC has detected 6,000 cases of H5N1 in wild birds, and over 58 million poultry birds have been affected[viii]. Of course, this means we should all take precautions, especially if you work closely with poultry. Do not touch sick or dead birds or wild animals. Instead, call it in and report it.

But what can we in public health do?

To quote Benjamin Franklin, “By failing to prepare, we are preparing to fail”, in other words the most important question we can ask ourselves as public health professionals is what can we do better to prepare for the next inevitable pandemic (be it H5N1 or something else)?

A combination of careful surveillance of birds and high-risk operations (such as mink farms), and potentially voluntary vaccination of high-risk workers with H5N1 vaccines could help prevent a pandemic. Notably, many of the H5N1 vaccines are incubated in chicken eggs. Since H5N1 has a 90-100% mortality rate in poultry according to the CDC, more vaccines, particularly mRNA vaccines, should be approved as quickly as possible[ix].

Vaccines that are quick to make are a very important part of a good pandemic preparedness plan. The United States keeps a relatively small stockpile of H5N1 vaccines—which makes sense because these vaccines lose potency over time—and plans to mass produce best-suited vaccines should the need arise. According to the global nonprofit, PATH, an mRNA vaccine can be synthesized in mere minutes[x], which could potentially substantially cut the time to mass produce H5N1 vaccines.

We are finally in a transition point of the COVID-19 pandemic[xi], but as much as many of us do not want to even think about another pandemic, this is exactly the right time to plan ahead.

That is it for today’s episode, thank you so much for listening! I hope you enjoyed it and learned something new. You know, if this story continues to evolve, we will likely revisit this topic, but tune in nest week to hear what else is happening in the world of public health. You can follow our podcast and like this episode wherever you’re listening from, and please visit us at publichealthpodcasters.com where you can build connections with other public health professionals through our career network membership, as well as access our other official PHPN pods.

I’m Lizzie Wilson, thanks again for listening.

[i] Agüero, M. et al. Eurosurveillance 28, 2300001 (2023). Accessed from: https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2023.28.3.2300001

[ii] Sidik, S. Bird flu outbreak in mink sparks concern about spread in people. Nature 614, 17 (2023), doi: https://doi.org/10.1038/d41586-023-00201-2

[iii] Anthes E. Bird Flu Outbreak Puts Mink Farms Back in the Spotlight. The New York Times (2023).

[iv] Human Infection with Avian Influenza A (H5) Viruses. World Health Organization (2023). Accessed from: https://www.who.int/docs/default-source/wpro---documents/emergency/surveillance/avian-influenza/ai_20230106.pdf?sfvrsn=5f006f99_108

[v] Tufekci Z. An Even Deadlier Pandemic Could Soon Be Here. The New York Times (2023). Accessed from: https://www.nytimes.com/2023/02/03/opinion/bird-flu-h5n1-pandemic.html

[vi] Steel J, Lowen AC. Influenza A virus reassortment. Curr Top Microbiol Immunol. 2014;385:377-401. doi: 10.1007/82_2014_395. PMID: 25007845.

[vii] Sun H, Li F, Liu Q, Du J, Liu L, Sun H, Li C, Liu J, Zhang X, Yang J, Duan Y, Bi Y, Pu J, Sun Y, Tong Q, Wang Y, Du X, Shu Y, Chang KC, Liu J. Mink is a highly susceptible host species to circulating human and avian influenza viruses. Emerg Microbes Infect. 2021 Dec;10(1):472-480. doi: 10.1080/22221751.2021.1899058. PMID: 33657971; PMCID: PMC7993395.

[viii] Current Situation. Centers for Disease Control and Prevention (updated February 8, 2023). Accessed from: https://www.cdc.gov/flu/avianflu/avian-flu-summary.htm

[ix] Bird Flu in Birds. Centers for Disease Control and Prevention (n.d.). Accessed from: https://www.cdc.gov/flu/avianflu/avian-in-birds.htm

[x] Verga D. mRNA and the future of vaccine manufacturing. Path (2021). Accessed from: https://www.path.org/articles/mrna-and-future-vaccine-manufacturing/#:~:text=An%20mRNA%20vaccine%20is%20synthesized,process%20performed%20with%20synthetic%20enzymes.

[xi] Blinken A. Secretary Antony J. Blinken At a Virtual COVID-19 Global Action Plan Ministerial. U.S. Department of State (2023). Accessed from: https://www.state.gov/secretary-antony-j-blinken-at-a-virtual-covid-19-global-action-plan-ministerial/

[12] Agüero, M. et al. Eurosurveillance 28, 2300001 (2023). Accessed from: https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2023.28.3.2300001

[13] Sidik, S. Bird flu outbreak in mink sparks concern about spread in people. Nature 614, 17 (2023), doi: https://doi.org/10.1038/d41586-023-00201-2

[14] Anthes E. Bird Flu Outbreak Puts Mink Farms Back in the Spotlight. The New York Times (2023).

[15] Human Infection with Avian Influenza A (H5) Viruses. World Health Organization (2023). Accessed from: https://www.who.int/docs/default-source/wpro---documents/emergency/surveillance/avian-influenza/ai_20230106.pdf?sfvrsn=5f006f99_108

[16] Tufekci Z. An Even Deadlier Pandemic Could Soon Be Here. The New York Times (2023). Accessed from: https://www.nytimes.com/2023/02/03/opinion/bird-flu-h5n1-pandemic.html

[17] Steel J, Lowen AC. Influenza A virus reassortment. Curr Top Microbiol Immunol. 2014;385:377-401. doi: 10.1007/82_2014_395. PMID: 25007845.

[18] Sun H, Li F, Liu Q, Du J, Liu L, Sun H, Li C, Liu J, Zhang X, Yang J, Duan Y, Bi Y, Pu J, Sun Y, Tong Q, Wang Y, Du X, Shu Y, Chang KC, Liu J. Mink is a highly susceptible host species to circulating human and avian influenza viruses. Emerg Microbes Infect. 2021 Dec;10(1):472-480. doi: 10.1080/22221751.2021.1899058. PMID: 33657971; PMCID: PMC7993395.

[19] Current Situation. Centers for Disease Control and Prevention (updated February 8, 2023). Accessed from: https://www.cdc.gov/flu/avianflu/avian-flu-summary.htm

[20] Bird Flu in Birds. Centers for Disease Control and Prevention (n.d.). Accessed from: https://www.cdc.gov/flu/avianflu/avian-in-birds.htm

[21] Verga D. mRNA and the future of vaccine manufacturing. Path (2021). Accessed from: https://www.path.org/articles/mrna-and-future-vaccine-manufacturing/#:~:text=An%20mRNA%20vaccine%20is%20synthesized,process%20performed%20with%20synthetic%20enzymes.

[22] Blinken A. Secretary Antony J. Blinken At a Virtual COVID-19 Global Action Plan Ministerial. U.S. Department of State (2023). Accessed from: https://www.state.gov/secretary-antony-j-blinken-at-a-virtual-covid-19-global-action-plan-ministerial/