BioEd Online

An update shows how the virus continues to expand its geographical range in mainland China.

H7N9 spreading far and wide

Cases of H7N9 avian influenza reported between 22 and 29 April show how the virus has spread in a week. The map also includes the risk for a similar avian flu virus, H5N1, with lower risk in light yellow and higher risk in dark yellow. Comparing the two epidemics may help researchers to target efforts to track and control H7N9.

Over the past week, the first two cases have been reported in Fujian province, far south of the main outbreak area around Shanghai and neighbouring regions on the eastern seaboard of China. One case was reported in Hunan province, and five in Jiangxi province, both southwest of Shanghai.

Human cases of the virus had already been reported in Beijing to the north, and in Henan province in the centre of the country. The total area in which human cases have been reported now spans some 1,700 kilometres north to south, and 1,000 kilometres east to west in eastern China. As of 29 April, China has reported a total of 126 lab-confirmed cases, including 24 deaths.

One case of H7N9 was reported in Taiwan on 24 April. However, the 53-year-old man is thought to have caught the disease in Suzhou in Jiangsu province in mainland China, so that is where his case is shown on the map.

The latest cases continue to fall mainly in areas designated as at increased risk for H5N1 avian flu. This seems to be consistent with the current thinking that birds — particularly poultry — and live-bird markets may be the main source of human infection. But the full risk factors for H7N9 remain unknown as yet.