Now also in the US: avian flu kills hundreds of seals – experts are concerned

A research team from Tufts University in Medford (USA) reports in the journal “Emerging Infectious Diseases” that hundreds of harbor seals and gray seals have died of H5N1 in New England in the northeastern US.

For some time now, the worst wave of avian flu ever documented among birds has been raging. It stretches across several continents. Tens of millions of animals have already died, especially seabirds. The circulating H5N1 line 2.3.4.4b is known to also infect and kill mammals such as minks, foxes, raccoons, martens and bears. Usually these are individual proofs.

In Peru, however, about 3,500 sea lions have recently died from the virus, according to Tufts University, and Canada reported a seal death off the St. Lawrence estuary. There are also reports from Russia of a similar event in seals in the Caspian Sea.

Here’s an overview of all the important questions about bird flu:

The team led by Wendy Puryear and Kaitlin Sawatzki was now evaluating pathogen analysis data on samples from dead, sick and healthy animals. Avian flu has been controlled in New England since January 2022 with testing in birds and some mammals. According to this report, in June and July 2022 alone, more than 330 harbor seals and gray seals died from avian flu strain 2.3.4.4b along the North Atlantic coast.

When the seals died in New England, the virus also hit the gulls particularly hard, the scientists explain. Sometimes there are pairs of monsters, sometimes literally from a bird and a seal on the same beach, Puryear explained. A seal can become infected if it comes into contact with the faeces of a sick bird or contaminated water, or if it eats an infected bird.

H5N1 is known to be nearly 100 percent lethal in waterfowl. The research now shows that this could also apply to mammals: all seals that tested positive for the virus were already dead by the time the sample was taken or succumbed to the pathogen shortly afterwards.

The question of whether the virus is also transmitted between seals is still under discussion. “It wouldn’t be surprising if transmission could occur between seals, as it has already happened with low pathogenic bird flu,” Puryear said. However, there is still no definitive evidence – for seals and for mammal-to-mammal transmission in general.

Experts are concerned that the virus could adapt better to mammals and therefore to humans. So far, only one death in China has been proven to be attributed to the currently circulating group of bird flu viruses. The Friedrich Loeffler Institute (FLI) recently reported that the woman who died in October had the H5N1 virus of group 2.3.4.4b. She was 38 years old and had contact with infected poultry. She developed severe pneumonia and died in hospital.

Experts were concerned about an outbreak of bird flu at a Spanish mink farm in October 2022. There were also similar reports of mass deaths among seals from Peru and Russia.

There is evidence in the animals that the pathogen has genetically better adapted to mammals, it said. It is not yet clear whether there was animal-to-animal transmission in the farm or via another route of infection, for example through food. Transmission from mammal to mammal would pose a greater risk to humans. (con/sda/dpa)