Health officials say they still don't understand how a lesser-known bird flu virus was able to kill two men and seriously sicken a woman in China, but that it's unlikely that it can spread easily among humans.
Two men in Shanghai became the first known human fatalities from the H7N9 bird flu virus after contracting it in February. A woman in the eastern city of Chuzhou remains in serious condition, China's National Health and Family Planning Commission said.
It was unclear how the three patients became infected, the health agency said. It sought to calm fears about the virus but provided few details about each case. Authorities have not described the patients' occupations or said whether they had come into contact with birds or other animals.