Beijing, Apr 23 (IANS/EFE): Chinese authorities reported another fatality from the H7N9 bird flu, bringing the toll from the virus in China to 21. The number of people infected stands at 104.

In addition, 13 patients have been released from the hospital after recovering from the disease.

The eastern metropolis of Shanghai continues to be the zone with the most deaths - 12 - while the neighbouring province of Zhejiang is the one with the most active cases, 40.

A team of experts from the World Health Organization over the weekend began investigating the origin and characteristics of the new strain of bird flu, which had not been detected in humans until last month.

All of the people infected with the virus have been quarantined and are being treated at specially designated hospitals, while authorities are insisting that, so far, there has been no indication of person-to-person infection, a circumstance which could be a very dangerous development in the progress of the disease and lead to a much wider epidemic.

China already has taken various measures to control the spread of the disease, including closing several markets where live poultry is sold in major cities around the country.

Also, the Chinese government last week ordered a halt in sales of wild birds to prevent the spread of the virus, and it prohibited direct contact between humans and animals at zoos.