Texas dairy worker tests positive for a mild case of bird flu: What physicians should know

By Stephanie Srakocic | Fact-checked by Davi Sherman
Published April 4, 2024

Key Takeaways

  • A dairy worker in Texas has tested positive for bird flu, marking the first case of human transmission in the US since 2022.

  • An outbreak of bird flu is developing among dairy cows in multiple states nationwide.

  • Reports of bird flu in mammals have increased in recent years, leading to concerns about virus mutations.

In March 2024, a baby goat in Minnesota tested positive for avian influenza, more commonly known as bird flu, marking the first case in US livestock. Reports of outbreaks among dairy cows in five states—Texas, Idaho, Kansas, New Mexico, and Michigan—began on March 25, 2024. On April 1, 2024, the Centers for Disease Control and Prevention confirmed that a person in Texas had contracted the virus.[][] 

The individual is a dairy worker who directly handled infected cows on the job. They have a mild case of bird flu, with eye inflammation as their only reported symptom. They are currently isolating and being treated with oseltamivir, an antiviral drug sold under the brand name Tamiflu. Approximately 15 additional dairy workers with flu-like symptoms and possible exposure have been tested for avian influenza, but only one worker tested positive.[] 

Bird flu is widespread among wild birds in the US and worldwide, but it rarely affects commercial flocks. However, outbreaks do occur. Poultry flocks in Utah and Montana experienced outbreaks in the fall of 2023, leading to the loss of over 100,00 commercial turkeys.[] 

Bird flu and mammals

Infections in mammals is also rare but has been documented. Reports of transmission to mammals have been increasing recently, including the current outbreak in the US, leading epidemiologists who study viruses such as bird flu to raise concerns that the virus might have mutated into a strain that is more easily transmittable among mammals.[]

Since this outbreak is new and ongoing, questions remain. There are multiple unknowns, including the method of transmission behind the outbreak. Donald Forthal, MD, Professor of Medicine and Molecular Biology and Biochemistry and Chief of Infectious Diseases at the University of California, Irvine, says that because the affected dairy farms are widespread, some of the transmission could be linked to birds, and not mammal-t0-mammal transmission. 

“There’s a possibility [that] the virus is being introduced at different times by birds flying over those areas. Given the sort of distance between, let’s say, Texas and Idaho, one would think that the birds probably have something to do with the introduction at both places independently,” Dr. Forthal says. “However, that remains to be seen.”

It’s also possible that the strain of bird flu tied to this outbreak passes more easily between mammalian hosts than previous strains. 

“This virus could be spreading directly from one cow to another. This is a virus that evolves quickly,” Dr. Forthal says, “and it’s hard to predict. It could evolve changes that are very large or very small.”

The risk of human transmission 

The CDC classifies bird flu as a low public health risk. The last known human transmission in the US occurred in April 2022, when a poultry worker culling infected bids contracted the infection. The poultry worker’s only reported symptom was fatigue, and they recovered quickly.[] 

Dr. Forthal says it’s a good sign that the dairy worker infected during this current outbreak only has mild symptoms. 

“That person had a pretty mild infection, and that’s very reassuring,” Dr. Forthal tells MDLinx. “If the virus has mutated to be effectively transmitted among cattle, those changes have not really changed the virus’s virulence and ability to spread in humans in a way that seems to be of major concern.” 

The risk of transmission to humans is still considered low. Between the beginning of 2022 and February 2023, there were only 15 reported cases of transmission to humans worldwide. People who work with animals, especially wild birds, are considered to be at slightly higher risk. The CDC advises that poultry workers take steps such as wearing gloves and respiratory protection such as masks to minimize this risk.[][] 

Physician guidance for suspected avian influenza

In light of the current outbreak, the CDC advises physicians to consider avian influenza as a possible diagnosis for patients who exhibit respiratory symptoms and have relevant exposure history. According to the CDC, this includes patients who:[]

  • Have come into contact with potentially or confirmed to be infected birds or livestock, including through consuming related food products.

  • Have had direct contact with water or surfaces contained with fecal matter, unpasteurized dairy products, or the remains of potentially infected animals.

  • Have experienced prolonged exposure to any potentially contaminated bird or other animal in a confined space.

Suspected avian flu should be reported to state health departments so that testing can be arranged. Physicians are also advised to collect a respiratory sample and encourage infected or potentially infected patients to isolate and consider starting an antiviral treatment. Guidelines for diagnosis, acceptable respiratory samples, and treatment courses can be found on the CDC’s website

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