A bird flu victim in Shanghai left hospital on Thursday (April 18) while China's health authority said they have been investigating the possibility of human-to-human spread of the virus.

The 66-year-old patient, Yang, said he has recovered from new bird flu strain, known as H7N9, and now he feels much better.

"I feel more energetic than I was when I was sent here. I was coughing and felt sick all day when I was in hospital. But later, I could eat more and I felt much better after a couple of day's of treatment. I even feared getting of bed to use the toilet (by myself), but now I can make it. So I feel much better now," said Yang.

He had been in a critical condition when first admitted to hospital.

Beijing health authorities announced on Wednesday (April 17) that Beijing's first two detected H7N9 patients have already left hospital.

China is investigating the possibility of human-to-human transmission of a new strain of bird flu that has killed 17 people and is examining "family clusters" of people infected with the virus, a top health official was quoted as saying.

Authorities have slaughtered thousands of birds and closed some live poultry markets to slow the rate of human infection. But many aspects of this new variety of bird flu remain a mystery, particularly whether the H7N9 strain is being transmitted between people.

China has warned that the number of infections, 82 so far, could rise. Most of the cases and 11 of the deaths have been in the commercial capital Shanghai.

The World Health Organization said on Wednesday that a number of people who have tested positive for a new strain of bird flu in China have had no history of contact with poultry, adding to the mystery about the virus that has killed 17 people to date.

Presented by Adam Justice