A person exposed to dairy cattle in Texas tested positive for H5N1 bird flu. The virus was first reported in dairy cows in Texas and Kansas by the USDA last month.

RT’s Three Key Takeaways:

  1. A person in Texas has tested positive for the H5N1 bird flu after exposure to presumed infected dairy cattle, marking the second such case in the US, with the first occurring in Colorado in 2022.
  2. The CDC considers the risk to the general US public from H5N1 bird flu to be low but recommends precautions for those with close or prolonged exposure to infected animals or environments.
  3. Avian influenza in dairy cows was first reported in Texas and Kansas by the US Department of Agriculture on March 25.

A person in the United States has tested positive for highly pathogenic avian influenza A(H5N1) virus—or bird flu—as reported by Texas and confirmed by the Centers for Disease Control and Prevention (CDC). 

This person had exposure to dairy cattle in Texas presumed to be infected with highly pathogenic avian influenza A A(H5N1) viruses. The patient reported eye redness, consistent with conjunctivitis, as their only symptom and is recovering. The patient was told to isolate and is being treated with an antiviral drug for flu. 

Risk Assessment and Recommendations

This infection does not change the H5N1 bird flu human health risk assessment for the US general public, which the CDC considers to be low. However, people with close or prolonged, unprotected exposures to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other animals, are at greater risk of infection. 

CDC has interim recommendations for prevention, monitoring, and public health investigations of HPAI A(H5N1) viruses.

CDC is working with state health departments to continue to monitor workers who may have been in contact with infected or potentially infected birds/animals and test those people who develop symptoms. CDC also has recommendations for clinicians on monitoring, testing, and antiviral treatment for patients with suspected or confirmed avian influenza A virus infections.

Historical Context

This is the second person reported to have tested positive for influenza A(H5N1) viruses in the United States. A previous human case occurred in 2022 in Colorado. Human infections with avian influenza A viruses, including A(H5N1) viruses, are uncommon but have occurred sporadically worldwide. 

CDC has been monitoring for illness among people exposed to H5 virus-infected birds since outbreaks were first detected in US wild birds and poultry in late 2021. Human illnesses with H5N1 bird flu have ranged from mild (eg, eye infection, upper respiratory symptoms) to severe illness (eg, pneumonia) that have resulted in death in other countries.

Widespread Presence and Agricultural Impact

H5 bird flu is widespread among wild birds in the US and globally. These viruses also have caused outbreaks in commercial and backyard poultry flocks and sporadic infections in mammals. 

Avian influenza in dairy cows was first reported in Texas and Kansas by the US Department of Agriculture (USDA) on March 25. Unpasteurized milk from sick cattle collected from two dairy farms in Kansas and one in Texas, as well as a throat swab from a cow in another dairy in Texas, tested positive for highly pathogenic avian influenza A(H5) viruses of the genetic clade 2.3.4.4b, which is the same clade that is widespread among birds globally. 

On March 29, USDA’s National Veterinary Services Laboratories confirmed the virus in a Michigan dairy herd that had recently received cows from Texas. 

Response and Research

The USDA Animal and Plant Health Inspection Service is providing regular updates on detections in dairy herds, as well as information on epidemiological findings and biosecurity guidance for farmers and veterinarians. Preliminary analysis of A(H5N1) viruses has not found changes that would make these viruses resistant to current FDA-approved flu antiviral medications, so these are believed to be effective against these viruses. 

Candidate vaccine viruses developed against related clade 2.3.4.4b viruses are available for vaccine manufacturing if necessary and preliminary analysis indicates that they may provide reasonable protection against H5N1 influenza viruses. Seasonal flu vaccines do not provide protection against these viruses. Analysis of virus samples is ongoing.

CDC is working with state and federal agencies, including USDA, the FDA, and local health authorities to further investigate and closely monitor this situation.

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