Avian flu has infected dairy cows in more than a dozen states – a microbiologist explains how the virus is spreading
The H5N1 avian flu has spread from birds to dairy cows, causing significant outbreaks and posing risks to farm workers and other animals, though pasteurized milk remains safe.
Last Updated on September 21, 2024 by Daily News StaffAlthough H5N1 typically infects wild birds, the virus has spilled over into domesticated animal populations, like dairy cows. Peter Cade/Stone via Getty Images
The Conversation U.S. asked immunologist and microbiologistJenna Guthmiller from the University of Colorado Anschutz Medical Campus to explain the historical roots of H5N1, its mode of transmission and how to avoid coming into contact with it.
What is H5N1?
H5N1 is a subtype of influenza A viruses. Other commonly known influenza A virus subtypes include H1N1 and H3N2, which cause seasonal outbreaks in humans.
Unlike H1N1 and H3N2, H5N1 largely infects wild birds, with waterfowl such as ducks and geese being the natural reservoirs for H5N1 viruses. Most H5N1 viruses are highly pathogenic avian influenza, meaning spillovers into other bird populations can lead to high mortality rates, including domesticated poultry.
H5N1 viruses were first identified in 1959 due to an outbreak in domesticated chickens in Scotland. In 1996, waterfowl were identified as the natural reservoir for H5N1.
Researchers have documented the current H5N1 strain in numerous mammals, with it largely affecting aquatic mammals like seals and scavenger mammals. Sporadic spillover to domestic mammals has been recorded, including to minks, goats and alpacas.
Dairy cow-associated H5N1 viruses have since jumped back into wild birds, and recent outbreaks in domestic poultry resembled H5N1 in dairy cows. Between May and July 2024, 13 confirmed H5N1 infections have occurred in humans, with all cases directly linked to dairy farms and poultry culling. https://www.youtube.com/embed/jhKI2Zskplg?wmode=transparent&start=0 The concern is that the virus could evolve to allow human-to-human transmission.
Why did the avian flu become more widespread?
It is unclear why H5N1 has become such a widespread problem. H5N1, like all influenza viruses, rapidly mutates to infect new hosts. However, H5N1 has several features that could increase its host range.
First, H5N1 viruses use a protein called hemagglutinin that allows H5N1 to infect with new hosts.
Lastly, H5N1 viruses are mutating genes associated with replication and immune evasion that are known to increase the infection of mammals.
Together, these factors could heighten H5N1 transmission and increase H5N1 spillover to mammals.
How is the strain transmitted to dairy cattle?
H5N1 viruses are largely causing infections in the mammary glands of cattle rather than the respiratory tract, which is the main site of infection for other influenza viruses in mammals. Recent studies have shown that the mammary tissue has receptors for H5N1, which could make this tissue susceptible to infection.
Since the infection is largely restricted to the mammary glands, researchers believe that H5N1 is being transmitted to cows by contaminated milk equipment, particularly the milking apparatus that attaches to the cow udders. Transmission across farms is due to infected cattle movement and shared equipment and personnel across dairy farms.
H5N1 does not pose a risk to the general public, as this virus is not known to transmit between people. As all known cases were those with direct contact with infected animals, people with occupational exposure to H5N1-infected cows and poultry continue to be at the greatest risk of infection.
People with occupational hazards should be aware of the H5N1 symptoms – similar to those of a cold – such as congestion, sore throat and fatigue, as well as conjunctivitis, more commonly known as pink eye. For more information, see the Centers for Disease Control and Prevention’s webpage on avian influenza in people.
Domestic and wild animals near dairy farms are at high risk of infection. Particularly, barn cats that have been fed raw milk have been reported dead on dairy farms with infected cows, with these animals coming back positive for H5N1.
In addition, spillover of H5N1 to other domesticated farm animals near infected dairy cows has been recorded.
What are the best ways to keep farm workers safe?
Using personal protective equipment, such as goggles and gloves, remains the best way to prevent the transmission of H5N1 to humans and from humans back to animals. People working around poultry or dairy cattle should also be aware of biosecurity measures, such as not wearing the same clothes and boots when traveling from one farm to another.
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How China cleaned up its air pollution – and what that meant for the climate
How China cleaned up its air pollution: Beijing’s air quality went from hazardous to good while Delhi and Lahore still struggle. Discover how China dramatically reduced pollution since 2013—and why cleaner air may have unintended consequences for global warming and climate change.
Delhi: 442. Lahore: 334. Beijing: 16. These are the levels of PM 2.5, one of the principle measures for air pollution, on November 19. As Pakistanis and Indians struggle with hazardous air quality, in Beijing – a city once notorious for its smog – the air quality is currently rated as good. Ahead of the 2008 Beijing Olympics, the Chinese government was so concerned about pollution that it introduced temporary restrictions on cars, shut down factories and stopped work on some construction sites. The measures worked and one study later found that levels of air pollution were down 30% during the period when the temporary Olympic restrictions were in place. It would take a few more years before the Chinese government implemented a clean air action plan in 2013. Since then, China has achieved a dramatic improvement in its air quality. In this episode of The Conversation Weekly podcast, we speak to Laura Wilcox, a professor at the National Centre for Atmospheric Science at the University of Reading in the UK, to understand how China managed to clean up its air pollution. But Wilcox’s recent research uncovered some unintended consequences from this cleaner air for the global climate: the pollution was actually helping to cool the atmosphere and by taking it away, it may have accelerated global warming. Wilcox explains:
What we’re seeing is a removing of cooling that’s revealing warming that’s already there. So the air pollution isn’t the cause of the warming. It’s just letting us see stuff that we’ve already done.
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The Hong Kong high-rise fire shows how difficult it is to evacuate in an emergency
Hong Kong High-Rise Fire: The deadly Hong Kong fire exposes critical challenges in evacuating tall buildings. Learn why stair descent is slower than expected, how human behavior causes delays, and what modern safety features can save lives.
Evacuations of high-rises don’t happen every day, but occur often enough. And when they do, the consequences are almost always severe. The stakes are highest in the buildings that are full at predictable times: residential towers at night, office towers in the day. We’ve seen this in the biggest modern examples, from the World Trade Center in the United States to Grenfell Tower in the United Kingdom. The patterns repeat: once a fire takes hold, getting thousands of people safely down dozens of storeys becomes a race against time. But what actually makes evacuating a high-rise building so challenging? It isn’t just a matter of “getting people out”. It’s a collision between the physical limits of the building and the realities of human behaviour under stress.
It’s a long way down to safety
The biggest barrier is simply vertical distance. Stairwells are the only reliable escape route in most buildings. Stair descent in real evacuations is far slower than most people expect. Under controlled or drill conditions people move down at around 0.4–0.7 metres per second. But in an actual emergency, especially in high-rise fires, this can drop sharply. During 9/11, documented speeds at which survivors went down stairs were often slower than 0.3 m/s. These slow-downs accumulate dramatically over long vertical distances. Fatigue is a major factor. Prolonged walking significantly reduces the speed of descent. Surveys conducted after incidents confirm that a large majority of high-rise evacuees stop at least once. During the 2010 fire of a high-rise in Shanghai, nearly half of older survivors reported slowing down significantly. Long stairwells, landings, and the geometry of high-rise stairs all contribute to congestion, especially when flows from multiple floors merge into a single shaft. Slower movers include older adults, people with physical or mobility issues and groups evacuating together. These reduce the overall pace of descent compared with the speeds typically assumed for able-bodied individuals. This can create bottlenecks. Slow movers are especially relevant in residential buildings, where diverse occupants mean movement speeds vary widely. Visibility matters too. Experimental studies show that reduced lighting significantly slows down people going down stairs. This suggests that when smoke reduces visibility in real events, movement can slow even further as people hesitate, misjudge steps, or adjust their speed.
Human behaviour can lead to delays
Human behaviour is one of the biggest sources of delay in high-rise evacuations. People rarely act immediately when an alarm sounds. They pause, look for confirmation, check conditions, gather belongings, or coordinate with family members. These early minutes are consistently some of the costliest when evacuating from tall buildings. Studies of the World Trade Center evacuations show the more cues people saw – smoke, shaking, noise – the more they sought extra information before moving. That search for meaning adds delay. People talk to colleagues, look outside windows, phone family, or wait for an announcement. Ambiguous cues slow them even further. In residential towers, families, neighbours and friend-groups naturally try to evacuate together. Groups tend to form wider steps, or group together in shapes that reduce overall flow. But our research shows when a group moves in a “snake” formation – one behind the other – they travel faster, occupy less space, and allow others to pass more easily. These patterns matter in high-rise housing, where varied household types and mixed abilities make moving in groups the norm.
Why stairs aren’t enough
As high-rises grow taller and populations age, the old assumption that “everyone can take the stairs” simply no longer holds. A full building evacuation can take too long, and for many residents (older adults, people with mobility limitations, families evacuating together) long stair descents are sometimes impossible. This is why many countries have turned to refuge floors: fire- and smoke-protected levels built into towers as safe staging points. These can reduce bottlenecks and prevent long queues. They give people somewhere safe to rest, transfer across to a clearer stair, or wait for firefighters. Essentially, they make vertical movement more manageable in buildings where continuous descent isn’t realistic. Alongside them are evacuation elevators. These are lifts engineered to operate during a fire with pressurised shafts, protected lobbies and backup power. The most efficient evacuations use a mix of stairs and elevators, with ratios adjusted to the building height, density and demographics. The lesson is clear: high-rise evacuation cannot rely on one tool. Stairs, refuge floors and protected elevators should all be made part of ensuring vertical living is safer.Milad Haghani, Associate Professor and Principal Fellow in Urban Risk and Resilience, The University of Melbourne; Erica Kuligowski, Principal Research Fellow, School of Engineering, RMIT University, and Ruggiero Lovreglio, Professor in Digital Construction and Fire Engineering, Te Kunenga ki Pūrehuroa – Massey University This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Wishing you all a Happy Thanksgiving! As we gather with loved ones to express gratitude and share a meal, let’s take a moment to appreciate the blessings in our lives. It’s a time to reflect on the goodness that surrounds us and cherish the moments of joy and togetherness. Whether you’re celebrating with family, friends, or even virtually, may this Thanksgiving be filled with warmth, love, and laughter. Let’s remember to extend kindness and lend a helping hand to those in need, spreading the spirit of gratitude and generosity. Enjoy the holiday and create beautiful memories. Happy Thanksgiving!
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Gemma Ware, Host, The Conversation Weekly Podcast, The Conversation This article is republished from The Conversation under a Creative Commons license. Read the original article.
