Confirmed infections in both wild and domesticated birds in Japan have jumped suddenly in late January, with five new cases identified on just the 25th and 26th of the month, Mainichi Japan is reporting.
Areas infected have spread from Hokkaido in the far north, to Kyushu in the south, forcing the culling of thousands of birds.
Experts are split as to why there are so many bird flu cases this year, with some saying the jump is because the virus has become more widely established in East Asia, while others believe particularly cold winds on the Asian mainland have forced more birds and more bird varieties to cross over to Japan than normal.
“Wild ducks that were probably infected by domestic poultry birds on mainland East Asia have, after their breeding season, come to winter in Japan and the Korean Peninsula,” says University of Tokyo ornithology professor Hiroyoshi Higuchi. Higuchi adds, that the genotype of the virus infecting birds in Japan is very similar to that found on the mainland, and it is now widely believed that migratory birds brought the disease to this country.
The Ministry of the Environment has pointed out that the number of wild bird species vulnerable to influenza now in Japan has risen to 33. However, the virus may also be spreading via smaller wild birds such as sparrows and even mice with infected bird droppings stuck on their bodies introducing the virus into domesticated birds’ supplies of drinking water.