The nation's poultry farms and relevant ministries are on high alert over bird flu, with farmers busy inspecting and disinfecting chicken coops.
The tension is due to a series of cases in which highly pathogenic avian influenza viruses have been detected in migratory birds.
No such viruses were detected in the three previous seasons, but four cases have already been reported since November this year. A season is defined as October to May of the following year.
In some Asian nations that serve as stopovers for migratory birds, the viruses have been spreading throughout poultry plants and other facilities.
The H5 and H7 strains are among the highly toxic varieties of bird flu. Although it does not usually infect people, some rare cases of human infection have been reported in China and other countries.
Poultry farms nervous
"There's nothing we can do to stop migratory birds from coming," said a 35-year-old female employee of a poultry farm in Saitama Prefecture. "I'm concerned that birds carrying the virus could enter the poultry housing."
The farm's chicken facilities, which are home to about 7,000 birds, are covered with netting to prevent the intrusion of wild birds. These nets are checked often and mended immediately if any tears are discovered. Access to the housing is restricted to staff only, and workers' boots are sanitized regularly to prevent the transmission of viruses.
A farming centre of the Tokyo Development Foundation for Agriculture, Forestry and Fisheries, in Ome, Tokyo, raises an original breed of silky fowl known as Tokyo Ukokkei and sells chicks to poultry farmers.
The centre has been keeping anyone who is not a staff member away from the chicken coop, and employees must put on special work clothes before entering the facility.
"If an outbreak were to occur at the centre, the Tokyo Ukokkei would be extinguished," said one worker.
2011 pandemic revisited
This season's first highly pathogenic flu virus in a migrating bird was found in Yasugi, Shimane Prefecture, on Nov. 13. It was followed by additional cases in the town of Nagara in Chiba Prefecture and Tottori. In the first case, the H5N8 subtype was detected in the droppings of migratory Bewick's swans. On Nov. 29, the virus was found in a debilitated white-naped crane in Izumi, Kagoshima Prefecture, the nation's largest wintering spot for cranes.
The previous time that a highly pathogenic virus was detected in migratory birds in the nation was in May 2011. During that season, the number of confirmed infections reached 60. As the infections spread to poultry farms, about 1.85 million birds had to be slaughtered in nine prefectures, including Miyazaki, Aichi and Chiba.
In April this year, bird flu was confirmed at a poultry house in Kumamoto Prefecture, though the case's relation to migratory birds is not clear. About 110,000 specimens were culled.
"Avian flu viruses have been confirmed one after another since late autumn, and the situation looks similar to the pandemic four years ago," said an Environment Ministry official.
Outbreak in Asia
There is also growing concern about bird flu due to the spread of infections in Asian nations that serve as stopover spots or breeding sites for migratory birds that fly to and from Japan.
South Korea has experienced continuous epidemics over the past year since last season, according to the Agriculture, Forestry and Fisheries Ministry. The number of domestic chickens infected with flu viruses reached a record high of 245 after January, and at least 14 million birds were slaughtered. In China, about 50 cases of highly pathogenic flu viruses have been detected since September.
In response, the Environment Ministry has tightened monitoring by raising the nationwide bird flu alert level from 2 to 3, the highest level, and increasing the frequency of virus tests. The agriculture ministry issued a statement to prefectures across the nation requesting thorough measures to prevent infection, stating that any poultry farm can fall victim to an outbreak of bird flu, and emphasizing the heightened alert.