Bird flu infection spreads, affecting dairy cattle and one farm worker

Another avian flu outbreak has struck a number of farms across the U.S., even affecting one farm worker, the CDC announced last week.

Dairy cattle are affected in seven states — Idaho, Kansas, New Mexico, Texas, Michigan, and Ohio — according to the CDC report .

The human infection was caused by a highly dangerous strain of avian influenza called A(H5N1) likely transmitted by coming into contact with affected dairy cows, according to the CDC.

The CDC has provided temporary recommendations on how to prevent, monitor, and investigate potential cases of humans getting infected with the virus.

Background

A worker on a commercial dairy farm in Texas developed conjunctivitis around March 27, 2024, and subsequently tested positive for the virus infection, reported the CDC. The viruses have been found in dairy cattle and wild birds in the area. However, there have been no previous reports of HPAI virus transmission from cows to humans.

The infected patient experienced conjunctivitis as the sole symptom and did not require hospitalization. The patient received antiviral treatment and is currently recovering in isolation.

No other cases of the virus infection associated with the current infections in dairy cattle and birds have been reported in humans, and there has been no human-to-human transmission of the virus, reported the CDC.

The CDC has conducted genetic sequencing of the virus and compared it to sequences from cattle, wild birds, and poultry. While minor genetic changes were found in the patient's virus sequence compared to those from cattle, neither the cattle nor human sequences possess the changes necessary for better adaptation to infect mammals.

There were no markers indicating influenza antiviral drug resistance in the patient's virus sequences. The virus is closely related to two existing HPAI A(H5N1) vaccine candidate viruses that manufacturers can already use to produce vaccines if needed.

This is the second confirmed case of the virus infection in the United States. The first case was reported in April 2022 in Colorado, and the individual had contact with infected poultry.

Current Risk and Recommendations

The risk to the general public from these viruses remains low. However, individuals with job-related or recreational exposures to infected birds, cattle, or other animals face a higher risk of infection and should follow appropriate precautions outlined in CDC recommendations.

The CDC continues to collaborate with the USDA, FDA, and state health departments to monitor individuals exposed to animals infected with HPAI A(H5N1) viruses.

The FDA has no concerns about the safety or availability of pasteurized milk products nationwide, as pasteurization effectively inactivates bacteria and viruses like influenza viruses.

Recommendations

The CDC provides updated recommendations for clinicians, state health departments, and the public. Clinicians should consider the possibility of HPAI A(H5N1) virus infection in patients displaying signs or symptoms of acute respiratory illness or conjunctivitis, along with relevant exposure history.

Isolation of the patient, infection control measures including personal protective equipment, and prompt initiation of antiviral treatment with oseltamivir are recommended.

Individuals with potential exposure to HPAI A(H5N1) virus-infected birds or animals should be monitored for respiratory illness symptoms.

Close contacts of infected individuals should receive antiviral chemoprophylaxis with oseltamivir twice daily, per CDC recommendations.