A new case report sheds light on the first documented transmission of bird flu from cow to human.
RT’s Three Key Takeaways:
- The case involved a dairy farm worker in Texas who contracted the highly pathogenic avian influenza virus (H5N1), or bird flu, from close interaction with infected cattle on the farm. Symptoms initially manifested as pinkeye in the worker’s right eye.
- Medical evaluations of the affected worker revealed a subconjunctival hemorrhage and serous drainage in the right eye, but no respiratory symptoms. Laboratory tests confirmed the presence of the same strain of bird flu circulating in the cattle, indicating transmission from cattle to human.
- Despite the worker’s infection, his condition improved with oral oseltamivir treatment (Tamiflu) and home isolation. Additionally, none of his household members, who received antiviral treatment as a precautionary measure, were infected. Viral sequences from both the worker and the infected cattle showed primarily avian genetic traits, with no mutations increasing human transmission risk, although a mutation associated with viral adaptation to mammalian hosts was identified.
A case report published in the New England Journal of Medicine provides new insights into the rare transmission of the highly pathogenic avian influenza, or H5N1, virus from dairy cattle to a human.
The affected individual, a dairy farm worker in Texas, experienced initial symptoms of redness and discomfort in his right eye in late March 2024, according to the report by Texas health officials and the Centers for Disease Control and Prevention. The worker had been closely interacting with both healthy and ill cattle on the farm. The affected cattle displayed symptoms like reduced appetite and decreased milk production, which are consistent with H5N1 infections observed in other animals. The man had repoted wearing gloves but no eye or respiratory protection.
Medical evaluations revealed a subconjunctival hemorrhage and serous drainage in the worker’s right eye. However, his vital signs remained stable, and he exhibited no respiratory symptoms. Laboratory tests using real-time reverse-transcription–polymerase-chain-reaction from conjunctival and nasopharyngeal swabs revealed he had the same strain of bird flu that was circulating in cattle.
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The worker was placed in home isolation and treated with oral oseltamivir (Tamiflu). The following day, the worker reported no symptoms apart from discomfort in both eyes; upon reevaluation, it was discovered that the worker had subconjunctival hemorrhage in both eyes, with no associated visual impairment.
His condition improved over the following days without any respiratory symptoms, and no household members—who were also given an antiviral as a precautionary measure—were infected.
Viral sequences from the Texas dairy worker and cattle retained primarily avian genetic traits, the authors wrote, and showed no mutations increasing human transmission risk. However, the viral sequences had a mutation (PB2 E627K) associated with viral adaptation to mammalian hosts, seen in past human and animal H5N1 infections and other bird flu subtypes.
No genetic traits were found in the virus that would reduce its susceptibility to US Food and Drug Administration-approved antiviral drugs for influenza, the authors stated.
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