The World Health Organisation has warned of a new strain of bird flu. There has been nothing like it since the killer virus of a decade ago.
US President Barack Obama has spent the day in Thailand at the start of a three-day tour of Southeast Asia.
Barack Obama is touring Southeast Asia to showcase foreign policy achievement and reinforce the U.S. role as a counterweight to China.
A wholesale chicken meat dealer told me his sales have dropped by 90%, despite official advice that cooked meat does not pose a bird flu risk.
Scientists are watching the H7N9 virus closely to see if it could spark a global pandemic but say there is little evidence so far that it can spread easily from human to human.
In comparison, the earlier bird flu strain, H5N1, is known to kill up to 60 of every 100 people it infects.
Experts said they still are not sure how people are getting infected but said evidence points to infections at live poultry markets, particularly through ducks and chickens.
However they added that it was encouraging that reported infections appeared to slow after the closure of live poultry markets in affected areas.
The World Health Organisation's (WHO) top influenza expert, Dr. Keiji Fukuda, said that people appear to catch the latest 'bird flu' virus, H7N9, from birds more easily than the H5N1 strain that began ravaging poultry across Asia in 2003.
Health experts are concerned about H7N9's ability to jump to humans, as well as the strain's capacity to infect birds without causing noticeable symptoms - making it difficult to monitor its spread.
"This is definitely one of the most lethal influenza viruses we have seen so far," Dr Fukuda said. But he added that experts are still trying to understand the virus, and that there might be a large number of mild infections that are going undetected.
The H7N9 bird flu virus has infected more than 100 people in China, seriously sickening most of them and killing more than 20, mostly near the eastern coast around Shanghai.
President Barack Obama said the relationship between the United States and China is "cooperative and constructive" and that it is important the two nations set "clear rules of the road" for trade and investment.
Obama and China's outgoing premier Wen Jiabao held a meeting at a summit of Asian countries taking place in Cambodia.
Despite tensions between the two economic powerhouses, President Hu Jintao said he and Obama share the view that the US-China relationship is one of the most important in the world.
Hillary Clinton, who is on her last presidential trip before she steps down as Secretary for State, told reporters the Asia tour had been "bittersweet".
She said: “It’s been great. It’s been bittersweet, nostalgic, all the things you would expect.”
President Obama put his arm around Burma's opposition leader Aung San Suu Kyi on the latest stop in his tour of South East Asia.
He also met the country's president Thein Sein - the man who has begun gradually embracing reform.
Speaking at the home where Ms. Suu Kyi spent years under house arrest, Mr Obama said something was happening in the country that could not be reversed.
ITV News' International Editor Bill Neely reports:
President Obama has arrived in Cambodia after visiting Burma. He is the first incumbent US President to visit the south-east Asian nation.
During a speech at the University of Yangon, President Obama told the people of Burma: "You gave us hope, and we bore witness to your courage."