Hundreds of dead seals have been washing up on Germany's North Sea coast since the beginning of October. Researchers have now found the cause of death: the avian flu virus.
Since early October, 609 dead or dying seals have been found on the coasts of the German North Sea islands of Sylt, Heligoland, Amrum and Föhr.
"That is more than we normally find," Hendrik Brunckhorst tells DW. Brunckhorst is a biologist and spokesman for the Schleswig-Holstein Wadden Sea National Park, a favorite habitat for the seals.
Typically, according to Brunckhorst, one to two thousand seals wash ashore in this part of Germany every year. Six hundred in less than a month, therefore, is indeed an "increased death rate."
The number of unreported cases is far higher, since only a percentage of the dead animals are actually found: Most of them are lost in the oceans.
Avian flu for seals
National park authorities have declared that the increased death rate is due to an avian flu virus of the strain H10N7. Researchers of the University of Veterinary Medicine Hanover discovered the virus in the dead seals' bodies.
H10N7 can infect all kinds of birds. So far, it has occurred among turkeys and emus in the United States, among farmed Peking ducks in South Africa, and chickens in Canada und Australia.
"This is the first time we have verified this virus in our seals," Brunckhorst says.
Most of the infected animals died of pneumonia caused by bacteria, Brunckhorst says. This often occurs as a secondary ailment when the animals catch the flu virus.
Even though this virus has never been found in seals before, it is not unusual for seals to be infected with different kind of viruses.
Brunckhorst still remembers the last outbreak of phocine distemper in 2002: The virus infected thousands of animals, and about half of national park's seal population died as a result. Seals from the polar sea had originally introduced the phocine distemper virus to those in the North Sea.
Now, it is an influenza virus - and one that has probably spread from Denmark. Seals around Anholt and the Danish Wadden Sea are also dying at a much higher rate than usual.
Researchers at the Technical University in Frederiksberg in Denmark confirmed that these animals were infected with the same flu strain as the seals in Germany.
'Not an epidemic yet'
For the moment, authorities remain relatively calm.
"We have a seal population of about 12,000 animals here in Schleswig-Holstein," Brunckhorst says. "That some of them die is very normal. At the moment, we're not even calling it an epidemic yet."
The World Wide Fund for Nature (WWF) shares this opinion. The seal population is not threatened, the organization writes on its website. "At this state of knowledge, we have to assume that this is a natural process and that there is no danger of a mass mortality," said Hans-Ulrich Rösner, a Wadden Sea expert with WWF who's based on the North Sea.
And in any case, there's nothing authorities can do, Brunckhorst says. "Even if there was a vaccine, we wouldn't be able to vaccinate thousands of wild marine animals."
Beachgoers, however, should be careful not to touch any dead or dying seals, say the national park authorities.
The animals can carry diseases that may also infect humans.