China said it was mobilizing resources nationwide to combat a new strain of bird flu that has killed six people, as Japan and Hong Kong stepped up vigilance and the United States said it was closely monitoring the situation.
All of the 14 reported infections from the H7N9 bird flu strain have been in eastern China and at least four of the six dead are in the financial hub of Shanghai, a city of 20 million people.
The strain does not appear to be transmitted from human to human but authorities in Hong Kong raised a preliminary alert and said they were taking precautions at the airport. Vietnam banned imports of Chinese poultry.
In Japan, airports have put up posters at entry points warning all passengers from China to seek medical attention if they have flu-like symptoms.
A total of 14 people in China have been confirmed to have contracted H7N9, all in the east of the country. One of the cases was a four-year-old child, who was recovering, the official Xinhua news agency said.
Hong Kong authorities said six people had died.
Authorities in Shanghai also discovered the H7N9 virus in a pigeon sample taken from a traditional wholesale market, Xinhua added, believed to be the first time the virus has been discovered in an animal in China since the outbreak began.
In the United States, the White House said it was monitoring the situation and the Centers for Disease Control and Prevention (CDC) said it had started work on a vaccine if it was needed. It would take five to six months to begin commercial production.
But the groundwork is being laid.
The virus has been shared with World Health Organization (WHO) collaborating centers in Atlanta, Beijing, London, Melbourne and Tokyo, and these groups are analyzing samples to identify the best candidate to be used for the manufacture of vaccine - if it becomes necessary.
Any decision to mass-produce vaccines against H7N9 flu will not be taken lightly, since it will mean sacrificing production of seasonal shots.
That could mean shortages of vaccine against the normal seasonal flu which, while not serious for most people, still costs thousands of lives.
Sanofi Pasteur, the world's largest flu vaccine manufacturer, said it was in continuous contact with the WHO through the International Federation of Pharmaceutical Manufacturers and Associations (IFPMA), but it was too soon to know the significance of the Chinese cases.
Preliminary test results suggest the new flu strain responds to treatment with Roche's drug Tamiflu and GSK's Relenza, according to the WHO.
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Shadow of SARS
With the fear that a SARS-like epidemic could re-emerge, China said it was pulling out the stops to combat the virus.
"(China) will strengthen its leadership in combating the virus ... and coordinate and deploy the entire nation's health system to combat the virus," the Health Ministry said in a statement on its website (www.moh.gov.cn).
In 2003, authorities initially tried to cover up an epidemic of Severe Acute Respiratory Syndrome (SARS), which emerged in China and killed about 10 percent of the 8,000 people it infected worldwide.
China "will continue to openly and transparently maintain communication and information channels with the World Health Organization and relevant countries and regions, and strengthen monitoring and preventative measures", the ministry said.
Other strains of bird flu, such as H5N1, have been circulating for many years and can be transmitted from bird to bird, and bird to human, but not generally from human to human.
So far, this lack of human-to-human transmission also appears to be a feature of the H7N9 strain.
"The gene sequences confirm that this is an avian virus, and that it is a low pathogenic form (meaning it is likely to cause mild disease in birds)," said Wendy Barclay, a flu virologist at Britain's Imperial College London.
"But what the sequences also reveal is that there are some mammalian adapting mutations in some of the genes."
Regions near the affected zone have begun taking precautions.
In Hong Kong, authorities activated the preliminary "Alert Response Level" under a preparedness plan for an influenza pandemic, which calls for close monitoring of chicken farms, vaccination, culling drills, and a suspension of imports of live birds from the mainland.
All passengers on flights in and out of Hong Kong were being asked to notify flight attendants or airport staff if they were feeling unwell.
Vietnam said it had banned poultry imports from China, citing the risk from H7N9.