Health authorities are monitoring 88 people who came into contact with the H7N9 patients and have not found any additional infections so far, China's health agency said. Experts say that indicates that the chance of human-to-human transmission is low.
"It is very unlikely, because the virus has to break the species barrier and this is usually quite a difficult event. There has to be a lot of significant mutation," said David Hui, an infectious disease expert at the Chinese University of Hong Kong.
One of the male victims of H7N9, who was 87, became ill on Feb. 19 and died on Feb 27. The other man, 27, became ill on Feb. 27 and died on March 4, the Chinese health commission said. A 35-year-old woman in the Anhui city of Chuzhou became ill on March 9.
WHO's O'Leary said it was difficult to predict the lethality of the virus but such emerging viruses tended to be more severe in humans and authorities were always on the lookout for a virus that might cause a severe pandemic.
"This may be a dead-end ... there's a few sporadic cases, it's hard to transmit to humans and doesn't transmit from human to human," he said. "But what we want to watch out for is whether it is a virus that is both serious for humans and easily transmitted."
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