BEIJING - The World Health Organization (WHO) on Monday called on the public to remain calm, as human infections of new bird flu strain H7N9 are isolated and may remain so.

The small number of infections means that there is no wide-ranging public health concern at the moment, according to Dr. Michael O'Leary, WHO representative in China.

There is not yet substantial data to fully understand the nature of the virus and how it evolves, he said.0   It will take more time to find out whether other countries have had H7N9 infections, he said, adding that WHO expects authorities to test flu cases stemming from unidentified sources in order to find out if they are H7N9 infections.

China confirmed 21 H7N9 human infections as of Sunday. Six of the infected people have died.

Both WHO and Chinese health authorities have promised to closely follow the development of the situation.

The current cases were reported in three provinces in east China, as well as the municipality of Shanghai.

Authorities have not ruled out the possibility of animal and human infections in other regions, according to Liang Wannian, director of the H7N9 influenza prevention and control office under the National Health and Family Planning Commission (NHFPC).

Liang said the government has taken effective measures to monitor the infections and hospitals have stepped up preparatory treatment efforts.

"We are confident in controlling the spread of the virus," he added.

Medical experts said people should take precautions such as reducing contact with live birds, frequently washing their hands and going to the doctor as soon as flu symptoms are exhibited.