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Since 2020, a new outbreak of avian influenza A (H5N1) has wreaked havoc, decimating hundreds of millions of birds worldwide. Farms bear the brunt, with infected poultry having to be systematically euthanized. Many farmers even agree that this wave is the most destructive since the virus first appeared in 1996. The disease is not limited to birds: to date, it has already affected almost fifty species of mammals, including humans. The first human case of bovine infection was recently confirmed in the United States.
According to the World Health Organization (WHO), between January 2003 and March 2024, 888 people contracted avian influenza A (H5N1), and more than 50% died. The first human case in the United States was discovered in 2022 in a person who was in contact with infected poultry. Recently, last March, a another case was identified in a young 18-year-old farmer from Texas. The latter is the first American to contract the virus through infected dairy cattle.
Scientists at the Texas Biothreat Research Laboratory helped discover the virus through patient samples. The results of the analyzes were published in the journal New England Journal of Medicine. ”
This will lay the foundation for many future studies of virus evolution “, enthuses one of the researchers at the University of communicatedreferring to the published document.
Towards a human pandemic?
To date, all cases of avian influenza A (H5N1) in humans are the result of zoonotic transmission (ie from animals). The fact that the virus cannot infect us through the upper respiratory tract reduces the likelihood of human-to-human transmission. As for the case of the recently diagnosed Texas patient, he presented with ocular symptoms.
However, in the research paper, scientists point out the existence of a recent change in the gene of the PB2 E627K virus. This is a mutation known to increase the adaptability and virulence of the microorganism in the host, thereby facilitating its replication. This change, already detected in other infected people, was also observed in the case of a young Texas farmer. ” The virus identified in the worker sample showed a change (PB2 E627K) associated with adaptation of the virus to mammalian hosts “, the team writes in the document. If this mutation isn’t already alarming, it represents “the first step on the path to a pandemic,” according to Thomas Peacock, a virologist interviewed by the magazine. Nature.
Human infections: underestimated numbers
Although the young Texan’s infection is currently the only confirmed human case resulting from transmission via livestock, some experts believe the actual number of infected could be much higher. Peacock is one of those who share this opinion. Referring to the extent of the outbreak in cattle, the researcher said Nature that “there were almost certainly many more human cases than we think”. You should know that in the United States, 50 herds spread over 9 states have already presented confirmed cases of infection.
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The researchers’ estimates underscore the urgency of accelerating testing to better define how many people and livestock have actually been exposed to H5N1. This would help scientists and health authorities to assess the true scale of the epidemic and take concrete steps to control it. There is also an urgent need to know how the virus spreads between cattle, because if it happens through respiratory secretions, it would be more difficult to control the epidemic. It would also put farmers at greater risk of contamination.