The current strain of bird flu, H5N1, is accountable for the culling of tens of millions of native birds and has More than a dozen farm staff fell in poor health in 2024, most recently in Colorado.
The Conversation US asked Immunologist and microbiologist Jenna Guthmiller from the University of Colorado Anschutz Medical Campus to clarify the historical roots of H5N1, its mode of transmission, and how you can avoid exposure to it.
What is H5N1?
H5N1 is a subtype of Influenza A virusesOther known subtypes of the influenza A virus include H1N1 And H3N2that cause seasonal outbreaks in humans.
In contrast to H1N1 and H3N2, H5N1 mainly infects wild birds, with waterfowl comparable to geese and geese being the natural reservoirs for H5N1 viruses. Most H5N1 viruses are highly pathogenic bird fluwhich suggests that an expansion to other bird populations can result in high mortality rates, including domesticated poultry.
H5N1 viruses were first identified in 1959 during an outbreak in domesticated chickens in ScotlandIn 1996, waterfowl were identified as a natural reservoir for H5N1.
Since their discovery, H5N1 viruses have caused 4 major outbreaks: 1997, 2003-2005, 2015, and 2021 up to now. Outbreaks in 1997 and 2003-2005 led to significant impact for people.
Since 2003, almost 900 H5N1 infections have been registered in humans. Of these infections greater than half ended fatally.
Where did H5N1 originate?
The current outbreak of H5N1 began at the tip of 2021 and comes from the Virus that caused a serious outbreak in 2015.
Since 2021, H5N1 strains have spread to 6 continents via migratory birds. Impact on domestic poultry has led to Culling of tens of millions of native birds
Researchers have detected the present H5N1 strain in quite a few mammals, primarily affecting aquatic mammals. like seals and scavengersSporadic attacks on domesticated mammals have been observed, including mink, goats and alpacas.
In March 2024, the U.S. Department of Agriculture reported an outbreak of H5N1 in dairy cows during lactationAs of August 27, 192 herds in 13 states confirmed H5N1 positive.
Meanwhile, the H5N1 viruses related to dairy cows have again spread to wild birds, and up to date outbreaks in domestic poultry have been much like those in dairy cows. Between May and July 2024 13 confirmed H5N1 infections have occurred in humans, with all cases being directly related for dairy farms and poultry slaughter.
Why has bird flu spread a lot?
It is unclear why H5N1 has develop into such a widespread problem. Like all influenza viruses, H5N1 mutates rapidly and infects recent hosts. However, H5N1 has several characteristics that would broaden its host range.
First, H5N1 viruses use a protein called Hemagglutinin This allows H5N1 to contaminate recent hosts.
Second, my research group discovered a mutation in H5N1 viruses that caused the outbreak in dairy cows. enables hemagglutinin to bind more efficiently to its receptor.
Finally, H5N1 viruses are mutating genes related to replication and immune escape which might be known to increase the infection of mammals.
Together, these aspects could enhance the transmission of H5N1 and increase the spread of H5N1 to mammals.
How is the strain transmitted to dairy cows?
H5N1 viruses cause infections primarily within the mammary glands of cattle and never within the respiratory tract, which is the most important site of infection for other influenza viruses in mammals. Recent studies have shown that the Breast tissue has receptors for H5N1which could make this tissue vulnerable to infection.
Since the infection is essentially limited to the mammary glands, researchers assume that H5N1 is transmitted to cows through contaminated milking equipment, especially through the milking device attached to the cows’ udders. Transmission between farms is resulting from the movement of infected cattle And shared equipment and personnel on all dairy farms.
To reduce transmission, the USDA introduced testing requirements in April 2024 for when cows are transported across national bordersIn addition, Colorado, the state with the biggest variety of positive herds, requires weekly testing on farms To Identification of infected herds.
What risks exist for humans and other animals?
H5N1 doesn’t pose a risk to the overall population since the virus is just not transmissible from individual to individual. Since all known cases have been traced back to individuals who have had direct contact with infected animals, the best risk of infection stays for individuals who have had occupational contact with H5N1-infected cows and poultry.
People with occupational diseases should concentrate on the symptoms of H5N1 – much like those of a chilly – comparable to stuffy nose, sore throat and fatigue, in addition to Conjunctivitishigher often called pink eye. For more information, visit the Centers for Disease Control and Prevention Website on bird flu in humans.
Domestic and wild animals within the vicinity of dairy farms are at high risk of infection. In particular, deaths of barn cats fed raw milk have been reported on dairy farms with infected cows. These animals tested positive for H5N1..
In addition, transmission of H5N1 to other livestock within the vicinity of infected dairy cows is feasible. was recorded.
What is the very best approach to ensure the security of farm staff?
The use of non-public protective equipment comparable to safety glasses and gloves stays the very best approach to prevent transmission of H5N1 to humans and from humans to animals. People who work with poultry or dairy cattle must also concentrate on: Biosecurity measuresfor instance, by not wearing the identical clothes and boots when walking from one farm to a different.
Is drinking cow’s milk dangerous?
As long as you Consumption of pasteurized dairy productsThere isn’t any suspicion of infection in humans. Pasteurization may be very effective in killing any H5N1 viruses that get into the milk.
People should avoid raw or unpasteurized milk since the H5N1 virus has been present in very high levels in raw milk.
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