The H7N9 virus claimed another life yesterday, and health authorities said detecting and controlling its spread would be more difficult than other avian flu outbreaks because it has only a relatively mild effect on birds.
A 64-year-old man who developed a high fever on Wednesday was admitted to Ruijin Hospital in Huangpu district on Sunday and died that evening, Shanghai authorities confirmed yesterday.
Meanwhile in Jiangsu , an 85-year-old man in Nanjing and a 25-year-old woman in Zhenjiang were fighting for their lives, authorities said.
By last night, the virus had claimed seven lives and infected at least 24 people.
National Influenza Centre director Shu Yuelong said the challenge of preventing and controlling H7N9 infections was "very great".
Unlike H5N1 bird flu, which made birds very sick, studies indicated H7N9 only affected birds mildly, and they showed few if any visible symptoms. Humans, though, were far more seriously affected, Shu said yesterday at a joint briefing by the National Health and Family Planning Commission and the World Health Organisation.
Feng Zijian , head of emergency response for the national Centre for Disease Control and Prevention, advised the public not to buy live poultry and have it butchered at wet markets.
Millions of chickens have been culled since H5N1 jumped the species barrier in 1997 in Hong Kong and killed six of 18 people infected. Since then there have been sporadic outbreaks of H5N1, in which 60 per cent of victims have died, but without any human-to-human transmission.
Noting that H7N9 only recently jumped from poultry to people, Shu said: "It is more likely to infect humans than the H5N1 virus, but it is not as contagious as seasonal flu viruses."
H7N9 had mutated from three viruses, but it remained unclear how it may develop because flu viruses constantly change, Shu said. The country's 500 flu-monitoring hospitals and 400 laboratories would watch closely for changes in the virus.
The WHO said yesterday it did not advise special screening at border crossings, nor imposing travel or trade restrictions.
"So far, we really only have sporadic cases of a rare disease, and perhaps it will remain that way. So this is not a time for overreaction or panic," its representative in Beijing, Dr Michael O'Leary, said. "These are a relatively small number of serious cases with personal health [and] medical implications", but no public health implications.
The WHO had confidence in China's efforts to track and control the outbreak, he said, and was "very satisfied and pleased with the level of information shared".
Click on each balloon for more information on individual patients infected with the avian flu virus: blue, patients infected with the H7N9 virus under treatment; red, those infected with the H7N9 who have died; and pink, those with H1N1 avian flu virus.