Deadly bird flu kills swans in Japan

Japanese authorities have confirmed that four swans found last week were infected with the H5N1 strain of bird flu.

This latest outbreak is the first case of bird flu in Japan in over a year when the lethal H5N1 strain was discovered in a wild eagle on Kyushu island in southern Japan.

Three of the swans, which were all found on the shores of Lake Towada in northern Japan, have now died.

Japanese health authorities have been more vigilant following a number of bird flu outbreaks in South Korea over the past month and the swans were detected during routine bird checks.

The H5 subtype of bird flu was initially suspected but further tests on the dead swans found the deadly virus was the culprit.

Authorities say there are no poultry farms within a 10 kilometer (6 mile) radius of the area where the swans were found, and no reports of unusual incidents have been registered at other farms.

However authorities will carry out inspections on fifteen farms within a radius of 30 km (19 miles) of the site where the swans were found.

In South Korea authorities continue to battle with its worst outbreak of avian influenza and this week have reported another suspected bird flu outbreak at a chicken farm in Ulsan City.

If this outbreak is confirmed, it will be South Korea's first bird flu outbreak in the southeast region.

Since South Korea reported its first case in 2003, the virus has spread rapidly, with 20 cases of the H5N1 strain confirmed in poultry in under a month and this is despite more than 5 million chickens and ducks being culled.

Authorities have been concerned for some time that the virus could jump from South Korea into Japan, as migrating swans commonly fly to Japan from Siberia, in Russia in the autumn and then return north in the spring; however, at this stage it is unclear how the swans in Akita were infected.

To date no human deaths from the disease have been reported in either South Korea or Japan.

According to the World Health Organization at least 240 people have died from bird flu since 2003, and almost all were linked to contact with infected poultry.

While the virus remains a disease of birds, which is hard for people to catch, experts worry it will eventually mutate into a form that spreads more easily between humans, with the potential to kill millions worldwide.

The highly pathogenic, H5N1 bird flu strain has now killed tens of millions of birds since the first cases were reported in Hong Kong in 1997.