London: Since Chinese media reported late last month that avian flu virus H7N9 had killed two men in Shanghai, additional reports of the disease have emerged in eastern Anhui and Jiangsu provinces and the metropolis Hangzhou, triggering fears of an incipient pandemic. Three people have been killed by the virus. The remaining six are in critical condition.

The World Health Organization (WHO), which is monitoring the cases in cooperation with Chinese authorities, said the strain was not transmittable from human to human. China's state newswire Xinhua reported that almost 200 people who came into contact with infected patients had tested negative for the virus.

Among four people to contract the disease in Jiangsu province, only one of them a 45 year-old poultry butcher has had long-term exposure to fowl, state media reported on Tuesday.

One infected man in Hangzhou has died of the disease, China's state broadcaster CCTV announced via its official microblog on Wednesday afternoon. The other, a 67-year-old retiree, is in critical condition.

Two people in Shanghai died of the disease last month, according to Xinhua: an 87-year-old surnamed Li and 27 year-old pork butcher Wu Liangliang. The former's two sons, aged 69 and 55, were admitted to hospital with flu-like symptoms over a 10-day span in mid-February, according to the Shanghai Daily newspaper. Both have tested negative for avian flu.

"He was a perfectly healthy man who walked into hospital unaided and came out a dead body," said Wu's uncle, also surnamed Wu. Though Wu died on 10 March, for 20 days afterwards his family understood the cause was pneumonia until they saw the news on television. "We were not notified about the bird flu virus from the start to the finish, and didn't understand how a small cold could be fatal," said the uncle, who declined to give his full name when he was interviewed by the Guardian at Shanghai's Jingchuan vegetable market.

According to the uncle, Wu caught a cold in late February. After it persisted, he visited the Fifth People's hospital on 1 March, a 15-minute walk from the market and the site where another H7N9 fatality, 87-year-old Li, died on 4 March. Wu was put on a saline drip and returned home the same afternoon. When he didn't feel better the next day he repeated the action. Eventually, on 4 March he returned to the hospital and was diagnosed with a pulmonary infection, and was admitted to the hospital's respiratory department with pneumonia.

"The hospital just treated the disease as normal pneumonia, they didn't take it seriously enough", said Wu's uncle.

Before the recent spat of cases, H7N9 was not deemed transmittable to humans and other animals. Its more virulent, long-circulating cousin H5N1 has killed 360 people worldwide since it decimated poultry farms across Asia in 2003.

Public health authorities throughout eastern China have ordered hospitals, schools, nurseries and poultry farms to step up monitoring for flu-like symptoms. Vietnam has temporarily banned mainland poultry imports. Stock shares of Chinese poultry-meat producers have slumped on mainland markets.

On Wednesday afternoon, "bird flu" and "H7N9" were trending topics on China's wildly popular microblogging platform Sina Weibo, with over 40,000 searches each. Some users suggested that the disease had spread to Beijing, causing one hospital in the capital to issue a denial.

Others insinuated that bird flu may have been responsible for the deaths of thousands of pigs dredged from a Shanghai river last month. Shanghai authorities quickly rebuffed the claim, saying that 34 of the pig carcasses tested negative for H7N9.

A man in Anhui using the handle Fen1234 castigated Shanghai's health authorities for taking significantly longer to announce the first avian flu diagnosis than to deny its connection with the dead pigs incident."You're completely unscrupulous when working to absolve yourselves of any crimes," he wrote. "Yet when working to ensure the health of common people, for the sake of stability maintenance and political necessity ... you cover up whatever you can." The post has been forwarded over 5,000 times.