United States: Some scientists are especially concerned about the avian flu’s ability to spread from birds to cows and then to humans.
Such a situation is quite possible, and it has already happened twice in the United States after the spring of 2024 when the first cows in the country started contracting highly pathogenic avian influenza (HPAI).
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Investigators from Iowa State University have recently conducted a study based on two dairy cows in Texas that contracted the H5N1 strain to understand these transmissions.
The team discovered that in infected cow respiratory tissue and the mammary glands, the receptors were adopted by numerous flu strains, including those sourced from birds, pigs, and even humans, as sciencealert.com reported.
Since all those receptors are neighbors, if a virus infects a cell, it can ‘learn its secrets’ and transition to attaching to other receptors on the cell also, commonly found in humans most of the time.
As fatal to birds as bird flu may be, in cows, it appears to produce a sharp, short-term, and potentially non-fatal decline in milk output.
The United States dairy cows are the first to get infected in the world, and after migrating from birds, experts still don’t know how the virus passes on from one infected cow to the next.
What more has the study found?
In the new study, the authors identified the milking process as one way through which the infection spreads. It acknowledges the existence of H5N1-friendly receptors on the cells of cow mammary glands, which must go a long way in explaining the peculiar effect of the virus on the animals’ milk, as sciencealert.com reported.
According to the dairy workers, milk from an infected cow appears to be thick and different in color. If the milk has not been pasteurized and is raw, the scientists believe it is a channel through which one mammal transmits the virus to another, including our species.
According to the officials from the US Centers for Disease Control and Prevention (CDC), a high quantity of the H5N1 virus has been detected in contaminated cow milk, which they noted as “sporadic human infections with no ongoing spread will not change the CDC risk assessment for the US general public, which CDC considers to be low.”
Fortunately, the two dairy workers in the United States who were infected with the H5N1 virus from the dairy cows manifested mild symptoms and recovered from their sickness without transmitting it to anyone else.
However, when studied by experts, the pathogen that contaminated the two dairy workers did display some signs of adaptation to mammal bodies.
It is still uncertain if those adaptations are only observed in dairy cows or dairy workers; however, researchers at Iowa State University are interested in uncovering more about it, as sciencealert.com reported.
It is recognized that the Flu A viruses, such as H5N1, enter the cells with the help of receptors of sialic acids.
Thus, those viral strains adapted to infect birds have affinities for certain sialic acid receptors that are not as profound as those that evolved to infect mammals. Down to the species level, the influenza A viruses are rather picky about where they can anchor themselves in the cell.