China's death toll from the new H7N9 bird flu virus strain jumped to five yesterday, and the state-run news agency Xinhua has confirmed 14 human cases of the illness thus far, all in eastern China.

Before these cases, the H7N9 bird flu has not been previously detected in humans. According to the World Health Organization, there is no evidence of human-to-human transmission of the H7N9 bird flu virus, and it seems unlikely to reach pandemic status. However, flu viruses mutate quickly, and epidemiologists are closely tracking the H7N9 for any changes in its infectious capacity.

All but one of the five deaths from the H7N9 bird flu have been in Shanghai, reports Reuters, and it seems that so far, the virus has only infected people who were in close contact with birds. Chinese disease surveillance authorities are working to identify the chain of transmission.

Xinhua reported that the Chinese Ministry of Agriculture identified the H7N9 bird flu virus in pigeon samples at a Shanghai poultry market, leading authorities to begin a mass slaughter at the market to prevent further exposure.

"It seems that whenever there's this spillover of bird flu to humans, it's associated with high numbers of poultry and intensive poultry production," said Trevon Fuller of UCLA's Center for Tropical Research to the Los Angeles Times.

A 48-year-old poultry transporter from Jiangsu province, near Shanghai, was one of the two who died of the H7N9 bird flu this week, and Xinhua reported that the three previous deaths were two male Shanghai residents, aged 27 and 87, and a 38-year-old man who worked as a cook in Jiangsu province.

A government can never be too careful about a potential pandemic, as Chinese authorities learned when they tried to cover up the early spread of Severe Acute Respiratory Syndrome (SARS) in 2003.

"If there is anything that SARS has taught China and its government, it's that one cannot be too careful or too honest when it comes to deadly pandemics," said Xinhua in a commentary. "The last 10 years have taught the government a lot, but it is far from enough."