FIGHTING FOR LIFE: A 55-year-old poultry stall worker receives intensive care at a hospital in Bozhou, Anhui Province, on April 8, a day after being diagnosed with H7N9 (LIU JUNXI)

The unprecedented human infection with a former animal flu virus has touched a raw nerve among the public and posed a challenge to China's disease control system, which is quickly responding to a possible outbreak by drawing upon experiences from previous epidemics.

As an influenza A virus, H7N9 normally circulates among birds. However, the Chinese National Health and Family Planning Commission (NHFPC) confirmed the world's first three human cases on March 30, including an 87-year-old male and a 27-year-old male in Shanghai who both died from pneumonia symptoms in early March. A 35-year-old female in Anhui Province died on April 9.

According to the daily update of the NHFPC on April 10, the country has reported a total of 33 cases, including nine fatalities. On the same day, a four-year-old boy in Shanghai became the first H7N9 patient discharged from hospital.

A total of 15 cases, including five deaths, have been reported in Shanghai. Jiangsu Province and Anhui reported 10 cases with one death and two cases with one death, respectively. Six cases have been reported in Zhejiang Province, with two deaths.

The commission said that no epidemiological link between those cases had yet been identified and those who have had close contact with people infected by H7N9 have been placed under medical observation, but hadn't shown signs of infection.

The commission also said that the country's confirmed H7N9 cases remain isolated and there are no signs of human-to-human transmission.

All identified H7N9 patients show initial symptoms of fever and coughing, which develop into severe pneumonia in later stages.

Measures taken

The Chinese Center for Disease Control and Prevention (CDC) said on April 10 that testing reagents for the H7N9 avian influenza virus have been distributed to all flu monitoring sites across the country and it also provided major infectious disease hospitals and research agencies with testing materials and detection methods.

The CDC said earlier that it is maintaining communication with health authorities in the United States and other countries and regions on relevant technological cooperation. It is also assessing the pandemic risks of H7N9 and working out coping strategies with relevant international experts.

The National Center for Food Safety Risk Assessment on April 7 urged preventive measures to ensure food safety, warning the public to avoid contact with potentially contaminated poultry.

The center also cautioned people to thoroughly cook eggs and poultry products, as it believes the virus cannot withstand high temperatures.

A laboratory under the Chinese Academy of Sciences (CAS) announced on April 10 that its researchers have ascribed the human infection to genetic reassortment of influenza strains caused by mingling of different bird populations during migration.

According to the researchers, the genetic reassortment is likely to have occurred in east China's Yangtze River Delta areas covering Shanghai, Zhejiang and Jiangsu, where a virus carried by migrating wild birds from the Republic of Korea and other regions in East Asia mingled with the avian influenza virus carried by local ducks and chickens.

Researchers also found that no H7N9 genes were traceable to pigs, thus excluding pigs as intermediate hosts for the deadly new strain of bird flu.

Both governments of Shanghai and Nanjing, capital city of Jiangsu, have suspended live poultry trade, shut down poultry markets temporarily and banned entry of live poultry from other parts of the country.

On April 4, the Shanghai Government ordered the culling of all birds in a live poultry trading zone of an agricultural products market after detecting the H7N9 bird flu virus in pigeon samples.

China's chief veterinarian Yu Kangzhen said on April 7 that infected poultry may show no symptoms at all of H7N9.

Yu told Xinhua News Agency on April 8 that H7N9 bird flu has not triggered an epidemic among poultry in China. Of the 738 samples collected from three live poultry markets in Shanghai on April 4 and 5, where the first known human deaths of the disease were reported, only 20 samples contained the H7N9 virus.

It was the first time the Ministry of Agriculture had detected the virus in animals in China.

Yu said that the possibility of infection among animals in other regions has not been ruled out and the Ministry of Agriculture has called for epidemic monitoring for animals across the nation and special attention to live poultry markets and poultry farms in affected areas. He pledged that the infected animals will be culled and their living environments will be disinfected in order to cut off the spread of the virus.

No need to panic

"Although we do not know the source of infection, at this time there is no evidence of sustained human-to-human transmission," the World Health Organization (WHO) representative in China Dr. Michael O'Leary said at a news conference held by the NHFPC on April 8.