Hong Kong’s health minister said on Monday that the city was on high alert for anyone infected with H7N9 avian flu virus after the mainland announced on Sunday three people had contracted the virus. The three people infected – two of whom died in Shanghai last month and one who is currently in critical condition in Anhui – are the first known cases of humans contracting the virus, previously found only in birds. Secretary for Food and Health Dr Ko Wing-man said in a radio interview on Monday that control measures and tests currently available would be effective in screening for the virus, especially the city’s border body temperature checks as all three mainland victims had fevers. “When medical staff come across suspected cases they will isolate them as soon as possible, and we have rapid tests that can diagnose H7 viral infections,” said Ko. Speaking of the mainland cases, Ko said that as tests showed the three had not infected each other, there was the possibility of more than one infection source and it iwas now important to look out for any epidemics among animals. Another important task, he said, would be to find out if there had been any human-to-human transmission. One of those who died in Shanghai was an 87-year-old man, whose two sons both contracted pneumonia, with one eventually dying of it. H7N9 had not been found in the either of them, but even if they were infected with the virus, it might not necessary mean human-to-human transmission, said Ko. When questioned about the Chinese government’s delay in reporting the cases, Ko said diagnosis involving the first cases of human infection usually took a long time.