Bird flu: H7N9 strain infects four more in China Patients arriving in Seoul from China are checked with thermal imaging equipment for high temperatures that might indicate infection with the H7N9 strain of bird flu. Photograph: EPA/Yonhap Chinese authorities have reported four new cases of a strain of bird flu previously unrecorded in humans that has already killed two people. The total number of known cases stands at seven. The World Health Organisation said on Monday there was no evidence that the H7N9 strain could be transmitted between people but that it was investigating the outbreak. The four new patients in China's eastern Jiangsu province were all in critical condition and receiving emergency treatment, the Xinhua news agency said, citing the Jiangsu provincial health bureau. A woman in Anhui province who caught the virus in early March is also in critical condition. The Chinese news website Chinanews.com said the four patients in Jiangsu - a province next to Shanghai - were aged between 32 and 83 and only one, a 45-year-old woman, had worked in the market slaughtering poultry. All four reported varying symptoms of dizziness, fever, coughing and breathlessness. China's National Health and Family Planning Commission on Sunday confirmed a Xinhua report that three people had been infected with the new strain. The two deaths were men in Shanghai aged 87 and 27 who fell sick in late February. It is not known how the seven victims were infected, though the government has said it believes the virus is not highly contagious. Xinhua said 43 people who had been identified as having been in close contact with the four patients in Jiangsu were under medical observation but had not developed flu symptoms. The WHO said on Monday that the first three cases had shown no evidence of human-to-human transmission but that there were questions to answer about the source of the infection and the mode of transmission. Ian Jones, a professor of virology at Britain's University of Reading, said at this stage there was no cause for alarm. At the moment I don't think it's anything more than an unusual set of isolated cases. He said three types of avian influenza - H5, H7 and H9 - were considered by experts to be a potential threat to humans. Since there was no evidence to date of human-to-human transmission, or of clusters of cases around those few confirmed so far, authorities should be watchful but need not enact emergency measures, Jones said. "Of course we need to take account of these cases and follow up the contacts and so on, but I think that's where it rests at the moment," he said. It's far too soon to assume this is the start of something.