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

Recently, in March 2024, an outbreak of highly pathogenic avian influenza (HPAI) subtype H5N1 was reported for the first time in dairy cows. This was the first time that these avian influenza viruses were detected in cattle. These outbreaks have spread across several US states and are in addition to those already observed across the globe in other mammals such as sea lions, cats and mink. In addition, as a consequence of the spread of the virus in livestock, infections have also been described in workers who have been in contact with infected animals, as well as other farm animals, such as cats and, of course, birds. The virus was also detected in cow's milk and it is thought that this could be a route of transmission.

In this good work by Kawaoka's prestigious group, the pathogenicity and transmission of a virus isolated from contaminated milk has been characterised. Two animal models widely used in the field, mice and ferrets, were used. Researchers have shown that animals can become infected by consuming contaminated milk and that vertical transmission occurs in suckling mice. However, the bovine H5N1 virus was transmitted inefficiently by the respiratory route in ferrets. Some of these results are similar to those obtained with other H5N1 viruses in the past. However, the researchers also point out that the virus isolated in the cattle outbreak possesses characteristics that may facilitate infection and transmission in mammals, including humans. This conclusion is mainly due to the ability of the virus to bind to cellular receptors present in the upper respiratory tract of humans.

Given the increase of cases in mammals that have been infected by avian influenza subtype H5N1 and the characteristic evolvability and adaptability of the influenza virus, the situation should continue to be actively monitored. In addition, it is important to assess the evolution of the virus and the functional significance of changes in its genome to identify possible adaptations to mammals, including humans.

Although the risk to the population, in general, is considered low, this situation could change in the future and we must remain vigilant. We must remember that recent influenza pandemics have had avian influenza as a key player.