4 years after the global pandemic of H1N1 influenza, a new type of avian influenza, H7N9, is emerging in mainland China. It was first reported in Shanghai on Feb 19, 2013. As of April 17, 2013, a total of 77 cases of H7N9 human infection have been confirmed, including 16 deaths. 30 cases, including 11 deaths, have been confirmed in Shanghai; 20 cases, including two deaths, in Jiangsu province; 21 cases, including two deaths, in Zhejiang province; three cases, including one death, in Anhui province; one case in Beijing; and two cases in Henan province.1, 2
The H7N9 virus is a new influenza virus subtype, and it has not been included in the statutory infectious disease surveillance reporting system of China. No vaccine has been launched yet. The source of H7N9 human infections is unclear, but based on past experience and epidemiological investigation, H7N9 virus might be carried by poultry, in their secretions or excretions. About 40% of the patients have not been in contact with poultry before. China’s official media, quoting Gregory Hartl (a WHO spokeperson), stated that although transmission of H7N9 virus between human beings has not been reported yet, there is a risk that mutations in the virus could ease the spread. Moreover, men who are smokers are a susceptible group because of their pulmonary dysfunction associated with smoking.3
The incubation period of the H7N9 virus is generally less than 7 days. Patients usually present with flu-like symptoms, such as fever, and cough with little phlegm, which can be accompanied by headache, muscle aches, and general malaise. Patients with severe progression of the disease manifest severe pneumonia, with body temperature over 39°C and difficulty breathing. The disease can progress rapidly, accompanied by acute respiratory distress syndrome, mediastinal emphysema, septic shock, disturbance of consciousness, and acute kidney injury.
H7N9 virus has attracted much attention. Chinese officials have actively responded to the infection, and introduced prevention and control measures. Shanghai, Nanjing, and some other places have suspended live poultry transactions and prohibited the entry of exotic live poultry. However, it is still a great challenge for the Chinese Government to control the infection. Unlike the SARS (severe acute respiratory syndrome) epidemic 10 years ago, H7N9 virus does not show signs of human-to-human transmission, and isolation of patients would not limit the transmission. Immediate culling of infected poultry is an effective measure. But more efforts must be made to prevent further spread of the infection.