UN experts yesterday called for the urgent testing of a flock of migratory birds in China after they found an outbreak of deadly avian flu was more lethal than previously thought.
A total of 5,000 birds have died in a bird sanctuary in northwestern Qinghai Province, five times more than previously reported, according to officials from the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) just back from visiting the area.
"This is the first time we've seen large numbers of migratory birds dying from bird flu [in the world]," said Julie Hall, the WHO official in charge of communicable diseases in China.
"So the virus has obviously changed to be more pathogenic to animals. What it means to humans we don't know," she told reporters in Beijing.
Some of the species infected in the outbreak discovered last month had not been affected by previous outbreaks in the region.
The officials expressed concern that China has tested only five of the 189 species of birds on the island and only 12 birds in total, all of them dead -- even though live birds pose a greater threat.
"I'm not so concerned about migratory birds if they just get very sick and die, but what concerns me the most is if we have many birds that are asymptomatic and they fly from here to 1,000km away," WHO China representative Henk Bekedam said.
That could affect other wild birds and domesticated animals, potentially devastating poultry industries.
The migratory birds are still on the island but will begin flying to other parts of China and to neighboring countries in August and September, presenting only "a small window of opportunity" to test them, experts said.
Chinese authorities have cordoned off a 50km radius around the "highly contaminated" nature reserve, restricting access and relocating residents, Hall said.
However, no cull has been carried out, as is often done with domesticated flocks, because some species are endangered, experts said.
"There [also] would obviously be logistical issues in trying to catch and kill them all," Hall said.
The five species known to be infected are bar-headed geese, great black-headed gulls, brown-headed gulls, ruddy shelducks and great cormorants.
Hall called for the immediate testing or electronic tagging of the animals to see which are infected and to trace where they are going.
"This is vital if we are to give an early warning to other countries before they come," she said.
The birds are expected to fly to the south and the west soon, but their migratory patterns are not clear, so other areas could also be under threat, FAO China representative Noureddin Mona said.
No human cases have been reported so far, but the fact the virus has now spread to new bird species could pose a greater risk for humans, Hall said.
"The more virus that's around, the more experience it has to experiment what it's like inside a human ... and the more chances it has to learn how to go from human to human," Hall said.
The H5N1 strain of bird flu has so far been mainly transmitted between animals, but it has also killed 54 people in Thailand, Vietnam and Cambodia since 2003.
WHO officials expressed concern that only two people have been tested in the outbreak, saying anyone who has been in contact should be tested.
They are also urging China to supply virus sequencing information to the international community "as quickly as possible," so experts can determine whether the virus has become more pathogenic to birds as well as humans.
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