# 1980
Flu viruses mutate. That's what they do.
By far, the vast majority of these mutations are either evolutionary `neutral' or `dead ends' for the virus. They do nothing to enhance its ability to infect or spread.
But over the past year we've seen changes in the way the H5N1 bird flu virus behaves in certain species of birds, indicating the virus has changed somehow.
Luckily, the mutation we all fear will give H5N1 the ability to easily infect, and pass efficiently among humans, has not yet occurred. Whether that mutation will ever occur is up for debate, but most scientists still believe the danger has not diminished.
Two and three years ago, ducks were assumed to be resistant to the bird flu virus. Over the past year in Indonesia and Vietnam, ducks have been found to be carriers of H5N1, capable of spreading the disease, but largely resistant to it's effects.
Asymptomatic birds are a seriously threat to detection and containment efforts. Sick or dying birds are sentinels, alerting farmers that something is wrong. When birds go on their way, spreading the virus, but not showing signs of illness our ability to control outbreaks diminishes.
Now, it seems, ducks are dying en mass in South Korea from the bird flu virus, but according to officials, they don't develop symptoms until late in the disease process, giving them ample opportunity to spread the virus.
With reports of wild birds, along with poultry flocks, being infected in South Korea, Japan, and China, Korean officials fear the virus is becoming endemic in Northeast Asia.
This from Chosun.com
Is Bird Flu Becoming Endemic in Northeast Asia?
Another suspected case of bird flu has broken out at a duck farm in Songpa-gu in southeastern Seoul, possibly also is of the highly pathogenic strain that can spread to humans, it emerged Sunday.
The Seoul city government in an emergency meeting decided to cull all poultry being raised outdoors within the city perimeter to prevent the spread of avian influenza. The city government mobilized about 600 officials to cull the poultry. Currently, the number of poultry being raised in Seoul is about 15,200 -- 11,700 chickens and 3,500 ducks.
With even Seoul being affected, now three Northeast Asian nations -- South Korea, China and Japan -- are being attacked by the highly pathogenic strain of avian influenza. Some worry that like Southeast Asia, Northeast Asia could be placed under constant threat of highly pathogenic bird flu.
Ducks, which had been relatively immune to bird flu, have turned out to be the source of the mutating disease. This has given rise to a vicious cycle of ducks spreading the disease to wild birds, which in turn infecting poultry again.
Ducks are walking time bombs since they show no symptoms for a considerable time. Unless Korea succeeds in preventing the spread of the disease via ducks and traditional poultry markets, the country could come under a permanent bird flu threat, experts worry.
This year's virulent strain is different from that of 2003 and 2004, and of 2006 and 2007 in that ducks have succumbed en masse this year, said Kim Chang-seob, chief veterinary officer of the Ministry for Food, Agriculture, Forestry and Fisheries. Mo In-pil, a professor of veterinary medicine at Chungbuk National University, said, "The original avian influenza virus didn't kill ducks. But it seems the mutant virus is."
Showing no symptoms, infected ducks can still be sold and bought at traditional poultry markets and spread bird flu across the country, Mo said. From them, the virus can spread to wild birds, in which the virus can mutate into a new strain; and this new strain then infects poultry and is capable of mutating yet again.
Experts believe China is already living constantly with a highly pathogenic bird flu virus by way of this vicious cycle of mutation. In China, large numbers of ducks have been infected by bird flu of a virulent strain, from Guangdong in May 2007, Tibet in January 2008 to Guizhou in February, and Guangdong and Tibet again in March..
Kim Jae-hong, a professor of veterinary medicine at Seoul National University, said, "China is already under constant bird flu attack because it has failed to prevent infected ducks from being sold at traditional markets. If Korea fails to take proper care of ducks and traditional markets, we too could find ourselves under constant attack."
It seems that the virus that caused domestic ducks to die en masse this year was imported from overseas. But if the virus mutates as the disease spreads, it is possible that a new highly pathogenic strain can break out without coming from overseas, Kim said.
In Akita and Hokkaido, Japan in April, wild swans died of bird flu of a virulent strain. But Kim Chang-seob said, "The Japanese don't raise many ducks, so there is little chance of bird flu spreading through ducks there."
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