Reacción a "The H5N1 avian influenza virus is transmitted between mammals from contaminated cow's milk and reaches the mammary glands"

In March this year, the first outbreak of H5N1 highly pathogenic avian influenza in cattle was announced. It occurred in the state of New Mexico (USA) and, as of May, 69 affected herds have been reported in nine other states. In parallel, several cats on affected farms have died and there have been three cases of farmers infected with conjunctivitis and respiratory symptoms.

This is a quantum leap in the ability of these highly pathogenic H5N1 viruses to transmit to other non-poultry animal species. Until now, transmission of this type of virus to various mammalian species, especially cats, mustelids, seals, elephants and sea lions, as well as a few hundred isolated human cases, had been reported. Fortunately, subsequent sustained transmission between individuals of these species is not very efficient, with the exception of those that have occurred in recent months in marine mammals off the coasts of South America and in the Antarctic region.

The novelty of this new episode, apart from affecting the bovine species for the first time, is the presence of the virus in the milk of infected cows, which facilitates a new route of transmission of the virus both to their offspring and, potentially, to the human species - only if the milk is not properly sanitised.

According to the authors of this experimental study, conducted in mice and ferrets, the ability to transmit through milk derives from the virus's ability to proliferate in the mammary gland. This new ability of the virus may have been produced by its ability to use appropriate cellular receptors as a result of its adaptation to mammals.

This first experimental approach will open up new studies carried out in the bovine species itself to reveal the pathogenesis of the infection, as well as the possibilities of transmission to other animal species and, especially, to humans as it is a key livestock species.