Indonesia has found traces of H5N1 bird flu in apparently healthy-looking poultry, making it tougher to detect the disease in the country hardest hit by the virus, officials said on Monday.
Sick or dead chickens are used as a sign of H5N1 infection, but the appearance of asymptomatic chickens means humans could become more easily infected with bird flu. Indonesia has the world's highest death toll from the disease, killing 79 people.
The poultry death rate is not so high, but there is a trend that chicken or poultry are infected by the virus but they don't die. So, the H5N1 virus is not fatal to poultry," Musny Suatmodjo, director of animal health at the agriculture ministry, told a news conference.
Bird flu is endemic in poultry in many parts of Indonesia, which has been struggling to contain the disease because millions of backyard chickens live in close proximity to people across the archipelago.
Contact with sick fowl is the most common way people become infected. Globally, 189 people have died of H5N1 infection since the virus reappeared in Asia in late 2003.
While bird flu is essentially a poultry disease, scientists are worried about the virus's ability to adapt to new environments and hosts. They fear this increases the chances of the virus mutating into a form that can jump easily between people, triggering a pandemic.
For the first six months of this year, 12,000 birds have died of bird flu or been culled, while last year about 1.75 million poultry either died of the disease or were culled, Suatmodjo said.
Authorities fear healthy-looking poultry could shed the virus in their feces, increasing the risk of spreading bird flu to people.
"The poultry deaths have come down. But there's something that we need to be cautious about. There is concern shedding may occur," Bayu Krisnamurthi, the bird flu commission chief, told reporters.
"There are some cases where humans were infected with the virus although there was no sick or dead poultry in their surroundings. But it can't be a general conclusion yet," he said, adding the commission was being cautious about this indication.
Hong Kong-based researchers have also detected such "asymptomatic" chickens and other poultry in mainland Chinese markets in recent years, which they believe were responsible for most of the H5N1 human infections there.
One published study of fecal samples taken from healthy poultry in markets in China in recent years found that one percent were infected with the virus.
The Indonesian Bird Flu Commission said last week the H5N1 bird flu virus in Indonesia might have undergone a mutation that allows it to jump more easily from poultry to humans.
(Additional reporting by Tan Ee Lyn in Hong Kong)
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