Now foxes have also died of bird flu. The Friedrich-Loeffler-Institut has confirmed that the virus was found in four dead animals at the National Reference Laboratory there. Four dead foxes in Germany – does this change the situation for people in this country? Probably not.

Pia Heinemann

Editor Nature and Science

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Infections in foxes with the currently almost worldwide rampant avian influenza virus H5N1 had already been reported in Sweden and Finland in recent years. The fact that mammals can become infected with the virus and also die from it is becoming increasingly apparent. H5N1 had been found in dolphins, otters, raccoons, bears and martens. Recently, mass deaths among seals and grey seals had caused a great stir: In a publication by a team led by Wendy Puryear and Kaitlin Sawatzki from Tufts University in Medford about a week ago in the journal "Emerging Infectious Dieseases", it was shown that in June and July 2022 alone, more than 330 seals and grey seals died of bird flu along the North Atlantic coast. This finding joins a mass death of 3500 sea lions in Peru, a seal death at the mouth of the St. Lawrence River in Canada and a similar event in the Caspian Sea.

It can no longer be overlooked that the bird flu virus is increasingly killing mammals. To what extent it has already adapted to a new class of animals is unclear. In the case of wild animals, the route of infection is usually not directly traceable – in all cases, including the four foxes from Lower Saxony, the animals could each have eaten an infected bird. Aquatic animals may also have contracted the virus via water contaminated by bird droppings; this route of infection has also been described by other avian influenza viruses.

Infections via prey or contaminated water would be less serious than if there had been an infection from seal to seal, from seal to seal – or even from fox to fox. All wild mammals infected so far eat birds or bird carcasses. For humans, however, these finds also mean: If possible, you should stay away from wild animals, be they healthy, sick or dead. If a dead wild animal is found, a responsible veterinarian should be informed.

The minks were the most disturbing

However, the scientists were particularly concerned about the case from Spanish mink farms: If the animals were not infected with food contaminated with bird droppings, for example, there is a possibility that the virus could spread from mink to mink in the farm. Neither has been proven. But if the mink-to-mink spread had taken place, H5N1 would have made the leap from bird to mammal world for the first time in Spain. In addition, researchers are particularly concerned about this, because the respiratory and immune systems of minks are very similar to those of humans. Ferrets, close relatives of minks, are therefore also used in research as model organisms in the investigation of respiratory infections. So far, no outbreaks have been reported from other mink farms.

Nevertheless, the authorities are concerned about the increasing number of mammals that have died of bird flu. Because with every infection there is the possibility that it comes to an adaptation that makes the virus dangerous for humans. The Lower Saxony Ministry of Agriculture therefore also used the four dead foxes to send districts with an increased incidence of infected wild birds to send dead or killed mammals to the responsible authorities and have them checked.

In the current bird flu outbreak, millions of wild birds have already died in recent years, the exact numbers no one knows. In contrast to previous outbreaks, there has been no decrease in the number of infections in the summer months, which means that large breeding bird colonies were also affected by the often fatal disease.

Even a few people have already been infected, most of them had close contact with birds. In most cases, the infection was very harmless, but according to the Friedrich-Loeffler-Institut there has already been one death: A woman in China has died of the H5N1 virus. She was 38 years old and had contact with infected domestic poultry. She contracted severe pneumonia and died in hospital.