Avian flu, threat of a future pandemic? Vigilance is more important than ever, experts say, in the face of signs of the virus mutating as it spreads among dairy cows and infects humans in the United States.
At this stage, there is nothing to say that this disease will one day be transmitted between humans, and American health authorities continue to consider the risk to the health of the general population to be low.
Avian influenza A (H5N1) appeared in 1996 in China, but since 2020, the number of outbreaks in birds has jumped, a growing number of mammal species have been affected as well as regions of the world previously spared , like Antarctica.
More than 300 million poultry have been killed in connection with the disease since October 2021, and 315 species of affected wild birds have been detected in 79 countries, the World Organization for Animal Health told AFP.
Mammals that ate infected dead birds, such as seals, also began to die en masse.
New development in March: cases of avian flu in several herds of dairy cows in the United States.
According to the Centers for Disease Control and Prevention, 58 people have tested positive for bird flu in the country this year, including two not previously exposed to infected animals.
In November, researchers reported that 8 out of 115 dairy workers tested in Michigan and Colorado had avian flu antibodies, suggesting an infection rate of 7%.
Several elements suggest that “avian flu is knocking on our door and could trigger a new pandemic,” Meg Schaeffer, epidemiologist at the American SAS institute, told AFP.
Several obstacles still prevent the H5N1 virus from spreading easily between humans, including the need to mutate to more effectively infect the lungs.
But the version of avian flu infecting American cows is just one mutation away from spreading more easily among humans, according to research published Thursday in the journal Science.
“One step” from “becoming more dangerous”
For virologist Ed Hutchinson, of Scotland’s University of Glasgow, this suggests that the H5N1 virus is only “a single step” away from becoming “more dangerous for us”.
Recent genetic sequencing of a Canadian teenager very ill with bird flu showed that the virus had begun to evolve to find ways to bind more effectively to cells in the body, the researcher told the Science Media Centre.
But, he said, “we do not yet know whether the H5N1 influenza virus will evolve into a human disease”, and other obstacles remain.
However, the more the virus is able to infect different animals and species, “the more likely it is that it will adapt to better infect humans,” warned Meg Schaeffer.
And if a bird flu pandemic were to break out, it would be “extremely serious” in humans, due to lack of acquired immunity, according to her.
Cases among U.S. farm workers have been relatively mild so far. But nearly half of the 904 human cases of H5N1 recorded since 2003 have been fatal, according to the World Health Organization.
Calling to “prepare for the possibility of an avian flu pandemic”, Maria Van Kerkhove, who heads the WHO’s Department of Prevention and Preparedness for Epidemics and Pandemics, judged at the end of November that “we are not still there” but that “we must redouble our vigilance”.
For Tom Peacock, virologist at Imperial College London, there are reasons not to be too pessimistic. Antiviral treatments and vaccines are thus available against avian flu, a major difference compared to Covid in 2020, he told AFP.
To avoid the worst scenario, several health experts have called for strengthening, particularly in the United States, controls, protective equipment for workers who may be exposed, but also the sharing of information.
On Friday, the U.S. Department of Agriculture announced a plan to test the milk supply for the avian flu virus.
Raw, or unpasteurized, milk is of particular concern because it has been found to be contaminated several times.
But Robert F. Kennedy Jr, vaccine skeptic chosen by Donald Trump as the next Minister of Health of the United States, is a fan.
Any possible lifting of restrictions on raw milk “would endanger human health”, according to Meg Schaeffer.
© Agence France-Presse
