What is the latest on Bird Flu?
Dairy cattle and poultry continue to get infected and there have been more human cases, but the risk to the public is still low.
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What is the latest on Bird Flu?
This information is correct as of January 13th, 2025, 12:00PM EST
Although dairy cattle and poultry continue to get infected and there are several more human cases, the risk to the general public is still low. Scientists and authorities are monitoring this closely and more testing of animals, humans and milk is underway.
Avian influenza, more commonly called bird flu, continues to infect poultry and dairy cattle in the United States. Human cases have also been found, however most of them are in farm workers who had direct contact with sick poultry or cows.
Let’s look at some US numbers (these are CDC laboratory-confirmed cases):
🐮 Cattle farms affected: 925 herds in 16 states
🐓 50 states and 1 territory (Puerto Rico) have outbreaks in poultry
🤕Human cases: 66 in total (40 in people exposed to cattle, 23 to poultry, 1 to other animal exposure and 2 unknown). Three of these cases were detected through the national flu surveillance system.
To date, most of the human cases have come from farm workers who are exposed to infected animals, but there are three known human cases in North America where the source of infection (i.e. the exposure) remains unclear:
One person in Missouri who was hospitalized back in the fall.
One teen in Canada who was severely ill and treated in the ICU. A recent report was released about their infection and details how many things the hospital staff did to help them survive. The teen is still in the hospital, but is no longer in the ICU. They had a version of bird flu that was similar to the version circulating in wild birds and in poultry farms in Canada. It is not the same version found in USA dairy cows.
One child in California who displayed only mild symptoms and has since recovered. The strain found is similar to that circulating in dairy cows.
Recently, one Louisiana case has made the news. This person was the first severely ill case in the USA and was exposed to sick or dead birds through their backyard flock. Unfortunately, they passed away from their infection. This is the first bird flu death in the USA.
None of these cases’ contacts have tested positive, which means human-to-human transmission remains unlikely at this point.
How are cases in humans being detected?
First, it is important to know that H5N1 would pop up initially as influenza A in tests because it is a type of influenza A. However, many other types of influenza A are circulating right now, so being positive for influenza A does not mean it is bird flu.
Human cases of bird flu are being identified through a few different methods.
The national flu surveillance system includes testing through public health laboratories. These samples are tested in a way that can detect H5N1.
Patients hospitalized with influenza A also have their samples tested to more specifically identify the type of influenza A causing their infection. This would detect H5N1. This is how the person in Missouri who had no known contacts was detected.
CDC and local health departments monitor people exposed to sick birds and dairy cattle and test them if symptoms develop. Not all exposed people may be getting this monitoring though, so increasing testing in exposed workers moving forward is critical.
Please note: wastewater monitoring is also important. But it cannot detect the source of H5N1 in the wastewater. It could be coming from humans, animals such as birds, or from milk products. Detection of H5N1 in the water is not enough to assume human-to-human transmission is happening.
Why are some cases mild and some cases severe?
A recent report was published in NEJM looking at bird flu cases in humans in the USA. It included 46 patients. 20 were infected by poultry, 25 presumed dairy cows and one with no known exposure source. All of these cases were mild and did not require hospitalization. However, we know from other reports that at least two people have been severely ill.
Why are we seeing different severity?
There are two genotypes (variants) of H5N1 circulating right now. One is causing an outbreak in dairy cattle in the USA and is called B3.13. So far, cases with this type have been mild. The second type is D1.1, which is causing an outbreak in wild birds and some poultry. So far, two cases with the D1.1 type (the British Columbia and Louisiana case) have both been severe. However, this difference alone may not be the cause. Other things can also greatly impact severity such as an individual's health history, how they were exposed, how much virus they were exposed to and genetic differences in the patients.
What about mutations?
The media has been going wild talking about some mutations found in the severely ill BC teen and Louisiana adult. It is true that analysis found evidence that the virus was mutating inside these two patients. They also noted that some of the mutations could help the virus better infect humans. However, this is not surprising. Viruses mutate the more they spread, which is why slowing cases is so important. It is also important to remember that there is no evidence these patients infected anyone else. They would need to spread the virus to others for this mutated version to survive past their infection.
California Public Health Emergency
On Dec 18th, 2024 Governor Newsome declared a State of Emergency in California regarding bird flu. This was not because the situation is more dangerous to humans, but because it gives resources for the state to better monitor, address, and contain the ongoing outbreak in dairy cattle.
Raw Milk Recall
The California Health Department has issued recalls for raw milk from Raw Farm, LLC, Valley Milk, and Desi Milk. Two cats died after exposure to the raw milk from Raw Farm.
Other Sick Animals & Raw Pet Food Recalls
Bird flu has also impacted animals in a zoo near Phoenix, Arizona, and has resulted in the death of some of their animals.
There have also recently been reports of bird flu impacting raw pet food from Northwest Naturals and Monarch Raw Pet Food, and at least one cat is thought to have died as a result.
What is the USDA doing about the issue with raw milk?
On Dec 6th, the USDA launched a National Milk Testing Strategy (NMTS). There are now 18 states included. Three states are noted to have positive samples from this testing system - California, Nevada, and Texas.
Reminder - although the risk remains low, here are a few things you can do to:
🚫Avoid raw milk and raw milk products. Pasteurized milk is safe as the pasteurization process kills the virus.
🚫Don’t feed raw milk or food products to your pets.
🚫Don’t let your pets play with sick or dead birds and if you find any dead wild birds report them.
🧤If you have bird feeders in the backyard, make sure to wear gloves when cleaning or refilling them and thoroughly wash your hands afterward.
🐮If you work or have contact with farm animals (including backyard chickens) please wear proper PPE because your risk of exposure is higher than the general public. CDC outlines resources for you here.
💉Make sure you are vaccinated for the flu to reduce the chance you are infected with multiple flu strains at once.
🇺🇸There are also many things the federal government can and should be doing to help. You can learn more from this article published by the nonprofit policy organization Rand.
Bottom line:
H5N1 is not going away anytime soon, but for now, the risk to most of the public remains low. We don’t want you to worry about this too much. Rest assured that we are keeping an eye on this and will update you with any important news or changes.
Stay safe. Stay well.
Love,
Those Nerdy Girls
Useful reading:
CDC - H5 Bird Flu: Current Situation
USDA - HPAI confirmed cases in livestock
CDC - Avian influenza technical update Dec 10
CIDRAP - Avian flu infects another California dairy worker as more raw milk positives prompt wider recall
CDC - Raw milk
Christina Pagel: Diving into Data And Decisionmaking - How close is a new bird flu (H5N1) pandemic?
Previous TNG posts about Bird Flu:
What is the latest on Bird Flu? - Dec’24
What’s the latest on Bird Flu? - Oct’24
What’s new with bird flu? — Sep’24
What’s new with bird flu? — July’24
Are there any updates on what’s happening with the current avian flu situation?
Is it safe to eat beef, given the avian flu outbreaks in cows?
Avian Influenza (H5N1) Update – May 15, 2024
Avian Influenza (H5N1) Update – May 8, 2024 — Those Nerdy Girls
Avian flu update – April 2024 — Those Nerdy Girls
ICYMI - Digest of Recent Posts:
Reproductive Health: How would the loss of mifepristone affect reproductive health care?
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