Q&A: What to know about bird flu in cattle, and the human case in Texas
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Key takeaways:
- Milk from dairy cows in several states tested positive for highly pathogenic avian influenza A(H5N1) virus.
- A person in Texas has also tested positive for the virus after having exposure to dairy cattle.
A person in Texas tested positive for highly pathogenic avian influenza after having exposure to dairy cattle that are presumed to also be infected with the virus, health officials reported.
The CDC said it has confirmed the positive human test for influenza A(H5N1) virus, also referred to as “H5N1 bird flu.”
The person, whose only symptom was eye redness, was treated with an influenza antiviral and is recovering, the CDC said. The patient was told to isolate while recovering, according to the agency.
It was only the second time a person in the United States has tested positive for H5N1 avian influenza. The first case occurred in 2022 in a Colorado worker who was involved in the culling of poultry presumed to be infected with H5N1.
The new case followed a recent report by the U.S. Department of Agriculture (USDA) that unpasteurized milk from sick dairy cows at two farms in Texas and Kansas — and a throat swab from another farm in Texas — had tested positive for the virus, and that cattle in New Mexico were showing similar signs of illness.
Although the virus is common among birds in the U.S and globally, human infections are rare, the CDC noted. According to the latest CDC data, 48 states have reported H5N1 outbreaks in poultry.
USDA officials said testing by the National Veterinary Services Laboratories has not found changes to the virus that would make it more transmissible to humans, indicating that the current risk to the general public remains low. The CDC also considers the risk to the general public to be low, but noted there is an increased risk among people with close or prolonged unprotected contact with infected birds or other animals.
For perspective on the new human case of H5N1, we spoke with Richard Webby, PhD, a faculty member in the department of infectious diseases at St. Jude Children’s Research Hospital and director of the WHO Collaborating Centre for Studies on the Ecology of Influenza in Animals and Birds.
Healio: Is this the same avian influenza virus (H5N1) that has been killing birds around the world?
Webby: Yes, it is essentially the same virus that has been circulating in birds with sporadic spillover to mammals in the U.S. for the past 3 years or so, which is also closely related to the virus circulating in many regions of the world.
Healio: Is it concerning that it now appears to have made the jump to dairy cows?
Webby: It’s really difficult to know what this means in terms of human risk. People obviously have more exposure to cows than we do to wild mammals, but so far, there isn’t any evidence that the virus in cows is any more infectious to humans than the viruses in birds. We really don’t know much about influenza in cows at all and what changes are likely.
Healio: The CDC and USDA said the risk to humans still appears to be low. Do you agree with that?
Webby: Yes, the virus is still very much a bird virus that has spilled over to cows — not a particularly human-adapted virus at all.
Healio: What signs do you look for in situations like this that would raise your level of concern?
Webby: Any evidence that this virus is continuing to circulate in cows, which I don’t think we know yet, would raise some concern levels. This would provide the virus with more chances to evolve.
Healio: What is the state of the current stockpile of H5N1 vaccine, in the event that we would need it?
Webby: The U.S. and some other countries do have stockpiles of H5 vaccine. There is not near enough for everyone but at least enough to offer to those at most risk, including health care workers.
References:
- CDC. H5N1 bird flu: Current situation summary. https://www.cdc.gov/flu/avianflu/avian-flu-summary.htm. Last reviewed April 2, 2024. Accessed April 3, 2024.
- Federal and state veterinary, public health agencies share update on HPAI detection in Kansas, Texas dairy herds. https://www.aphis.usda.gov/news/agency-announcements/federal-state-veterinary-public-health-agencies-share-update-hpai. Published March 25, 2024. Accessed April 3, 2024.
- Highly pathogenic avian influenza A (H5N1) virus infection reported in a person in the U.S. https://www.cdc.gov/media/releases/2024/p0401-avian-flu.html. Published April 1, 2024. Accessed April 3, 2024.
- U.S. case of human avian influenza A(H5) virus reported. https://www.cdc.gov/media/releases/2022/s0428-avian-flu.html. Published April 28, 2022. Accessed April 3, 2024.
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