European governments are bolstering their guard against bird flu, faced with a growing number of dead swans and the risk that migratory birds — which begin returning north next month — could bring the disease from Africa.
Concerns about the disease, and its possible threat to humans, have mounted.
“Avian influenza is a big threat,” Dr. David Nabarro, the U.N.’s top bird flu specialist, said Wednesday. “It is spreading throughout the world.”
Song birds are expected to start arriving in southern Europe from Africa in two weeks. They are judged to be less likely carriers of bird flu than ducks and other water fowl because song birds fly longer distances and tend to stay away from wetlands, where the disease is more prevalent. The migration period is heaviest in March and April, but runs into May for some species.
France, Germany, the Czech Republic, Switzerland and Sweden all took steps Wednesday to try to prevent the spread of the deadly H5N1 strain, ordering that domestic fowl be kept in screened, ventilated buildings, where they are less likely to come in contact with wild birds. Britain and the Netherlands have yet to record bird flu outbreaks, but ordered similar precautions.
Bird conservationists cautioned against a rush to judgment. They maintain that bird flu most likely reached Nigeria in poultry trade from Turkey and China. Veterinary specialists said they have yet to determine how the disease arrived in Africa, but that measures being ordered by European officials Wednesday were prudent.
The fear of birds migrating from Africa has been augmented by the deaths of swans from the Baltic Sea to the southern tip of Italy. Because of their susceptibility to bird flu, swans are among the first birds to die from the disease, giving an indication of where it is present, experts told The Associated Press.
The first swan deaths in Europe were recorded in Croatia in October, leading to controls on contacts with wild birds. In Austria, authorities said two swans found dead were infected with H5N1. At least nine dead swans have been found on Danish islands in the Baltic, and two swans died in Germany.
In Slovenia, a swan infected with bird flu was found dead last week. Laboratory tests are still under way to determine whether it is the H5N1 strain. Bulgaria has confirmed one swan death from H5N1 and is testing three others. The country has implemented disinfection of cars and shoes at the entrance to poultry farms.
Greece has four confirmed cases — in three swans and a goose — and Cyprus has a confirmed case in a chicken. Italy confirmed six swans died of the disease, which has also been detected in birds in Russia, Ukraine, Kazakhstan and Azerbaijan.
91 human deaths
Bird flu has killed at least 91 people since 2003, according to the World Health Organization. Almost all the human deaths have been linked to contact with infected poultry, but experts fear the H5N1 virus could mutate into a form that spreads easily among people, possibly sparking a pandemic.
Dr. William Karesh, director of the field veterinary program for the New York-based Wildlife Conservation Society, said it was likely the virus spread from Asia in a leapfrog fashion, with one bird picking it up from another, rather than one bird flying a long distance with the disease.
Experts are now concentrating on Nigeria, where three states have confirmed H5N1 among domestic poultry and five others have suspected cases. Scientists assume migratory birds brought the disease to Africa, but have yet to find proof.
“We don’t know how the disease got into Nigeria,” said Juan Lubroth, head of the infectious disease group at the U.N.’s Food and Agriculture Organization.
An FAO team is taking samples from wild birds in Africa to get a better idea of which birds may be carrying the virus.
But Lubroth said it will take four to six weeks to get results, and European officials are correct to take precautions in case migratory birds bring the disease from Africa.
“If there were an outbreak in poultry, it would be rapidly detected,” and the outbreak could be contained,” he said. “The situation could be a little more delicate on the eastern side of the Mediterranean, only because surveillance is not as strong as on the western side.”
Experts said, however, that it might be necessary to order the slaughter of birds or a vaccination program.
Christianne Bruschke of the Paris-based World Organization for Animal Health said the most likely birds to carry H5N1 from Africa would be ducks, because they can transmit the virus without getting sick.
“We think the virus has been brought into Africa by migratory birds, but we think that the virus will be transmitted on the ground more by trade, markets, transport,” she said.
Maria Cheng of the World Health Organization said the disease could continue to be primarily a bird affliction, but experts still fear it could mutate into a virus that could transmit easily among humans and cause a pandemic.
“After we saw H5N1 in Turkey, that drove home the point that we would not be able to predict with any accuracy where ... H5N1 would go next. It looks like it’s the same virus that was in western China last year that we saw in Turkey and also in Nigeria,” Cheng said.
“It’s clear that H5N1 is capable of going thousands of miles,” she said.