The World Health Organization (WHO) and Chinese health authorities have promised to closely follow the development of the H7N9 bird flu situation, suggesting the public should not panic.

At a press conference on Monday, WHO representative in China Dr. Michael O'Leary called on the public to remain calm. "Although we do not know the source of the infection, at this time there is no evidence of sustained human-to-human transmission," he said.

The small number of infections means that there is no wide-ranging public health concern at the moment, O'Leary said.

As of Sunday, China confirmed 21 H7N9 human infections, and six of the infected people have died. The current cases were reported in three provinces in east China, as well as the municipality of Shanghai.

O'Leary said there is not yet substantial data to fully understand the nature of the virus and how it evolves.

It will take more time to find out whether other countries have had H7N9 infections, O'Leary said, adding that the WHO expects authorities to test flu cases stemming from unidentified sources in order to find out if they are H7N9 infections.

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

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

"We have confidence in keeping the disease under control," he said.

Liang told the press conference that China has started development research of vaccines for the H7N9 bird flu virus.

However, complications in the development and manufacturing process mean it may take about six to eight months before a vaccine can be brought to market, he said.

Liang said the decision to put a vaccine into production will depend on whether the virus can mutate and become human-to-human transmissible.

"Vaccination is not the only effective way to prevent the disease," the director said.

Deng Haihua, a senior NHFPC official, said traditional Chinese medicine and treatment were also being considered in the commission's efforts to deal with the infection.

Feng Zijian, director of the emergency response center of the Chinese Center for Disease Control and Prevention, said authorities and medical staff are working on measures to identify and treat patients at an early stage to reduce the virus' mortality. He recommended the public reduce contact with birds and poultry.

At the press conference, Liang promised that China will report H7N9 cases to the WHO in a timely manner and increase cooperation with the organization.

The WHO and countries nearby to China, as well as Hong Kong, Macao and Taiwan, will be kept updated on the H7N9 bird flu situation, Liang said.

China reported the first case of H7N9 to the WHO soon after the case was confirmed, said Liang, adding that the country will accept site inspections, communicate with foreign experts, and provide strains of H7N9 avian influenza to the organization in accordance with International Health Regulations.

"We have maintained close cooperation with the WHO in clinical research and epidemiology, and will boost cooperation regarding the study of the virus, including its pathological condition, infection rate and recovery rate," he added.

O'Leary said the WHO had been in cooperation and communication with Chinese officials over the last two weeks.

"We are very satisfied and pleased with the level of information shared and we believe we have been kept fully updated on the situation," O'Leary said.

Compared to a decade ago when China fought the Severe Acute Respiratory Syndrome (SARS), it is now more prepared in handling public health emergencies, according to Liang.

The country's disease control network and related legislations have greatly improved in the past decade, with detailed response plans being implemented by both central and local governments, he said.

All-level governments have been urged to be more transparent in releasing information on H7N9 bird flu cases, Liang added.