BEIJING — Chinese authorities say two Shanghai men have died from a little-known type of bird flu in the first known human deaths from the H7N9 strain.

Medical officials say it's not clear how they were infected, but that there's no evidence of human-to-human transmission.

China's National Health and Family Planning Commission said on its website that a third person, a woman in Anhui province, also was infected and is in critical condition.

The medical commission says there's no sign that any of the three contracted the disease from each other, and no sign of infection in the 88 people who had closest contact with them.

H7N9 is considered a low pathogen strain that is not easily contracted by people.

China says the World Health Organization has been notified of the case.