Experts are worried about an outbreak of bird flu on a Spanish mink farm. They see signs that the H5N1 virus is adapting to mammals - and this could also make it more dangerous for humans.
The pathogens had previously been found in other mammal species - such as raccoons, foxes, martens or seals - said Thomas Mettenleiter, President of the Friedrich Loeffler Institute for Animal Health, the German Press Agency. So far, however, there have been individual events in which the virus has passed from a bird to a mammal.
With the outbreak in Spain in October 2022, however, it could be that "the pathogen really did spread from mammal to mammal - i.e. from mink to mink". Other researchers also believe that this is possible or even probable. The events in Spanish mink breeding could have been an indication of a further adaptation step of the virus, says Mettenleiter.
Housing conditions promote spread
The background to the concern is the currently rampant, largest ever documented wave of bird flu in birds, which extends over several continents. This gives the pathogen more opportunities to spread to mammals. In addition, the cramped conditions in which the mink were kept were conducive to such a possible spread among these animals, says Mettenleiter. Therefore, the event in Spain was "definitely a warning signal".
Tom Peacock, a virologist at Imperial College London, was even more drastic. "This is incredibly worrying," he told Science magazine. For him, this is "a clear mechanism for how an H5 pandemic could start".
Animals on a farm in the northwestern region of Galicia began dying in October last year, Science magazine reported. At first, veterinarians expected the coronavirus to be the trigger. But tests showed that the H5N1 virus had led to the deaths. As a result, the farm's more than 50,000 mink were killed and their carcasses destroyed. Farm workers themselves were not infected. An analysis of the case has just been published in the magazine "Eurosurveillance".
risk to public health
Since the receptors to which the virus docks in the respiratory tract of birds are rarer in mammals, they are usually spared from bird flu, according to "Science". However, animals could contract bird flu by ingesting wild bird droppings or preying on infected animals, Hualan Chen, a virologist at the Harbin Veterinary Medicine Research Institute in China, told Nature magazine. Spread among mammals, on the other hand, indicates that there is a greater risk to public health.
According to the "Science" report, it is not known how easily the virus found in mink can infect humans or spread between them. However, several mutations were found in virus samples from four animals. One of them contributes to the fact that the H5N1 virus can multiply better in mammalian tissue. However, no other known, worrying mutation was found.
Mink industry as breeding ground for virus mutations
The bird flu outbreak also highlights the risks of mink farming. Even the corona virus, which was brought into mink farms by humans, has spread rapidly among the animals. Researchers fear the mink industry could become a constant source of infection and a breeding ground for viral mutations.
Bird flu has been plaguing Europe on a regular basis for years. While the pathogen in connection with bird migration in the past appeared mainly in the cold season in this country, there have recently been infections throughout the year. The currently dominant virus is considered harmless to humans.