By Ian Ransom
BEIJING (Reuters) - A 16-year-old boy died of bird flu in central China Tuesday, the third death this year, as experts warned that lax monitoring could mask the true extent of the disease in Chinese poultry.
A health official Tuesday also confirmed the mother of a toddler infected with the avian virus from the same province had died of pneumonia weeks earlier.
After going almost a year without recording a case, four human infections have been reported in China in the last two weeks, as millions of people flock to poultry markets to buy food ahead of the Lunar New Year holiday.
Three have died and one remains in hospital.
The latest victim, a student, died in hospital in Huaihua, in central Hunan province, after falling ill in neighbouring Guizhou, another health ministry official said.
Chinese health authorities now say the patients in three of the four cases had had close contact with poultry prior to being infected. It was unclear whether the fourth case, a 27-year-old woman who died in eastern Shandong province on Saturday, had also come in contact with poultry.
With all the victims having fallen ill in different provinces without any prior reports of outbreaks among local bird populations, experts are concerned that surveillance gaps may be masking the true extent of the disease.
"Quite a few provinces now have human cases, so where is the source of the infection?" said Leo Poon, a virologist at the University of Hong Kong.
"The recent cases indicate that (the victims were directly infected by poultry) and that the outbreak of the disease in poultry may be very widespread. That increases the likelihood of people getting infected," Poon said.
The H5N1 flu remains largely a virus among birds, but experts fear it could change into a form that is easily transmitted among humans and spark a pandemic that could kill millions worldwide.
Since the H5N1 virus resurfaced in Asia in 2003, it has infected 397 people, killing 249 of them, according to WHO figures.
With the world's biggest poultry population and hundreds of millions of backyard birds, China is seen as critical in the fight to contain bird flu, and shares long, permeable borders with countries that regularly report outbreaks.
There were only three recorded cases in China in 2008, all of which were fatal. At least 34 people have been infected in China and 23 have died.
MORE CASES FEARED
A batch of smuggled Chinese chickens infected with bird flu made its way to neighbouring Vietnam, officials there said last week. An eight-year-old girl was taken to hospital after being confirmed infected with bird flu earlier this month.
H5N1 has also been found in dead poultry and wild birds in India's northeastern state of Sikkim, which borders China and Nepal, prompting authorities to launch an initial cull of some 15,000 chickens and ducks, an Indian veterinarian official said.
China's Foreign Ministry said health authorities had reported the cases to the World Health Organisation, but played down the bird flu problem at home.
"Relevant departments of the Chinese government are paying high attention to this issue. At this stage, the cases are individual and isolated," Foreign Ministry spokeswoman Jiang Yu told reporters at a regular briefing Tuesday.
The World Health Organisation said in a statement it was seeking more clarification from China. "There are still unknowns as to how these infections are occurring," Gregory Hartl, a spokesman from WHO's Geneva headquarters, told Reuters.
China's Agriculture Ministry Monday warned of more bird flu cases as poultry is shipped from region to region ahead of the Chinese New Year holiday next week.
China's State Administration of Industry and Commerce instructed officials to "severely punish" illegal sellers of live poultry and bird flu vaccines, the Farmers' Daily, a state-run newspaper, said in a report posted on its website (www.farmer.com.cn).
(Additional reporting by Ben Blanchard, Yu Le and Chris Buckley in Beijing, Tan Ee Lyn in Hong Kong, Biswajyoti Das in Guwahati and Stephanie Nebehay in Geneva; Editing by Nick Macfie and Sugita Katyal)
