The possibility that the H5N1 bird flu virus can be transmitted between humans has raised alarm bells in the United States.
Currently, the country’s authorities are investigating seven cases of people who were in contact with the first patient infected with bird flu without having been in contact with animals. At the moment it has not been possible to confirm that any of these people are infected by the virus, but they did present symptoms compatible with the disease.
However, a total of 94 health workers were in contact with Missouri’s “patient zero” and have not shown symptoms, so it is considered that there is a low probability that the H5N1 avian flu will be transmitted between humans.
Control strategies “are not working”
A recent investigation published in the journal ‘Nature’ warns that the control strategies for the avian flu virus (H5N1) “are not working”, so it is possible that there are variants that are “spreading silently” without be detected.
The study, led by researchers at the Pirbright Institute of Veterinary Sciences in the United Kingdom, analyzed recent outbreaks of the H5N1 virus in mink on fur farms in Galicia, in seals and sea lions in South America, and in dairy cow farms in the United States. where there are already more than 200 affected herds in 14 states.
Precisely in Missouri (United States), the first human case of avian flu was detected without contact with infected animals last August, which constitutes the fourteenth infection in humans reported so far this year in this country, although the 13 previous cases did correspond. to people exposed to infected animals.
Researchers have seen that virus surveillance strategies fail to report infection data, especially on cow farms in the United States, which leaves “huge gaps in control mechanisms.”
“The problem stems from the fact that in the United States it is only mandatory to declare avian flu in poultry, not in mammals. The Department of Agriculture only requires testing for the H5N1 virus when lactating livestock is moved from one state to another,” he emphasizes. one of the authors of the study, Thomas Peacock, a zoonoses specialist at the PirBright Institute.
Peacock warns of the contrast between the current lack of data on the spread of the virus on farms in the United States, and the exhaustive control that previous generations of ranchers in this country carried out with foot and mouth disease in cattle, thanks to which it was stopped completely. effective way.
How the virus is transmitted
Los US Centers for Disease Control and Prevention (CDC) explain that infected birds transmit the virus through saliva, mucous membranes and feces, and that other infected animals may have viruses present in their respiratory secretions, different organs, in the blood or other body fluids, including animal milk.
Infections in humans can occur when the virus reaches a person’s eyes, nose, or mouth or when the person inhales virus particles. This can happen when the virus is airborne (in droplets, small aerosol particles, and possibly dust) and settles on the mucous membranes of the eyes. It can also occur when a person touches an object contaminated with the virus and then touches their mouth, eyes or nose.
To date, 887 human infections and 463 deaths have been detected in the world, with a fatality rate of 52%.
In most cases, infection occurred through close contact with an infected animal.
The new H5N1 variant was detected in 2022 and since then the cases registered in the United States have been mild and without chains of contagion.
Invisible sprouts and vaccination
Scientists also warn of the risk that the analysis of the avian flu virus in wildlife focuses only on corpses, and no tests are carried out on live animals, “which implies that there may be H5N1 variants spreading silently without being detected”.
“The lack of data, and of decision and resources on the part of public administrations may be leading to invisible outbreaks spreading silently not only on farms, but among people who work with animals,” Peacok highlights in a statement.
In addition to more and better reporting of data, researchers consider that vaccination must also be resorted to, claiming that there are flu vaccines for poultry that, although they do not prevent contagion, do reduce the viral load of avian flu.
While remembering that “there are stocks of H5 vaccines related to circulating avian flu viruses that could be produced on a large scale using messenger RNA platforms if the H5N1 virus begins to spread in humans.”
“The severity of a future H5N1 pandemic remains unclear,” the researchers emphasize, because the low lethality of the latest human infections, compared to the last highly fatal outbreak that occurred in Asia, may be due to the fact that the infection occurred through the eye and not the lung.
Older people may be immune
Along those lines, they state that older people appear to have partial immunity to H5N1 due to exposure in childhood, but those born after the H3N2 pandemic of 1968 may be more susceptible to severe illness in an H5N1 pandemic.
So far, avian flu viruses have caused more documented global pandemics in human history than any other pathogen, researchers recall.
