The Japanese government confirmed another case of bird flu Monday, in a sign that authorities are having trouble stopping the virus from spreading among chicken farms.
Miyazaki prefecture, in the southern part of the country, said in a statement that one of five chickens found dead at a farm over the weekend tested positive for the H5 strain. Further tests were needed to determine whether it was the H5N1—which has caused the most disease and death in humans—or whether it was a less virulent strain of the avian flu, such as H5N2.
The case was the sixth confirmed report of bird flu in the prefecture since the first one was found earlier this month, which prompted the government to cull nearly 600,000 birds. The the first two cases in the prefecture in January were confirmed as the H5N1 strain, the government said.
No humans have been reported infected in Japan this flu season, which began in November.
Japanese Agriculture Ministry officials said the virus won't affect humans who consume meat and eggs from infected birds if the products are fully cooked. Infections among humans are largely caused by direct contact with infected birds.
"It's spreading quickly," said Koji Saito, spokesman for the department in charge of sanitation of livestock farming in Miyazaki Prefecture.
Experts said flu-infected wild birds were the most likely culprit, as the cases of bird flu are not concentrated in a single place, Mr. Saito said.
There have been seven cases of bird flu detected in Japan among wild birds such as swan and duck since October, six of which were confirmed as the H5N1 strain, according to the Agriculture Ministry's website.
In South Korea last week, two new cases were reported near Seoul, where 5.5 million birds at 40 locations have been culled since Dec. 31.
Two other prefectures—Kagoshima and Aichi—reported bird-flu outbreaks in January, with nearly 160,000 birds being culled in total. In November, Shimane Prefecture in western Japan also culled some 20,000 chickens.
This flu season has been one of Japan's worst since 2004, in terms of of the number of poultry killed.
In 2005, 5.78 million chickens in Ibaraki and Saitama prefectures outside of Tokyo were culled. In 2009, 1. 6 million were destroyed in Aichi located in the central Japan.
Japanese media last week reported that some inspections into bird-flu-stricken farms were conducted by a poultry farm's affiliated company, instead of by government officials.
Mr. Saito of the Agriculture Ministry cited staff shortages, as many officials were focused on last year's foot-and-mouth disease that led to the slaughter of of some 290,000 livestock.