Two men in Shanghai were reported to have died after contracting the H7N9 avian flu, marking the first known deaths from a rare and little-known type of bird flu.

Three cases have been reported - two in Shanghai and one in nearby Anhui province — with the third patient, in Anhui, in “critical condition”, said National Health and Family Planning Commission on Sunday.

An 87-year-old man and a 27-year-old man had died on March 4 and 10 respectively after developing a fever and “severe pneumonia”. Their cases were confirmed as H7N9 avian influenza on Saturday “based on clinical observation, laboratory tests and epidemiological surveys”, said the State-run Xinhua news agency.

The Commission said it was “unclear” how the infections were contracted, and that “no abnormalities” had been detected among 88 contacts of the three people.

The three cases are thought to mark the first known instances of the H7N9 flu being reported in humans. The Commission said tests of the patients’ contacts had shown there were no signs that the flu could be contagious. It, however, added that little research had been carried out on the rare flu so far and there was, as yet, no vaccine.