Epidemiological update: Seven new confirmed cases of novel influenza A virus, A(H7N9) in China, 5 April 2013

Since the last epidemiological update of 3 April, seven additional cases including two fatalities were reported by Chinese authorities. For the first time a child, aged four years, was reported. The other six cases are aged between 48 and 79 years. The date of symptom onset was 20 and 29 March 2013 for the two newly reported cases for whom it is available (Table 1 and Figure 2). No new provinces were affected.

There are now sixteen confirmed cases including six deaths. The median age is 50 years with a range between 4 and 87 years; six of them are females. The date of symptom onset of cases was between 19 February and 29 March 2013 (Table 1 and Figure 2). To date, four adjacent provinces are affected: Shanghai, Jiangsu (6 cases each), Zhejiang (3) and Anhui (1) (Figure 1).

Figure 1: Cumulative number of reported confirmed cases of novel influenza A(H7N9) by province, as of 5 April 2013, 15:00 CEST 

Disclaimer: ECDC is collecting data from official websites including WHO

Table 1: Number of influenza A(H7N9) cases by date of onset, age, gender, and province (n=16)

Figure 2: Number of cases by week of onset of symptoms from four Chinese provinces (n=13)

Note: the onset of symptoms is unknown for three cases

Five of the cases were reported to have had animal contact (four with poultry and one with pork). The source of infection is still unknown. Nevertheless, China's Ministry of Agriculture found an influenza A(H7N9) virus in a pigeon sample collected at the Huhuai wholesale agricultural products market in the Songjiang district of Shanghai. As of today, there is no evidence that human influenza A(H7N9) cases are related to this pigeon case. Further investigations are on-going. China's Ministry of Agriculture has closed the live poultry trading zone of the market and started slaughtering all the birds.

There is no epidemiological link between the cases. More than 500 close contacts of all cases are being followed up by the Chinese health authorities. One was reported as having fever and a runny nose, but no laboratory confirmation is available yet.

There is currently no evidence of sustained human-to-human transmission of the influenza A(H7N9) virus. ECDC continues to monitor the situation closely. More cases are expected to be reported.

This epidemiological update does not change the conclusions and recommendations of the ECDC’s Rapid Risk Assessment of 2 April 2013.