Since Oct. 2016, China has seen an increase in human infections with avian influenza A(H7N9) virus and the World Health Organization (WHO) looked at some of the recent scientific information in several categories.

H7N9 avian influenza/ Cynthia S. Goldsmith and Thomas Rowe-CDC
H7N9 avian influenza/ Cynthia S. Goldsmith and Thomas Rowe-CDC

Concerning the geographical distribution in animals: From December 2016, the Chinese national animal influenza virus surveillance program of the Ministry of Agriculture detected influenza A(H7N9) virus in birds in Anhui, Guangdong and Zhejiang provinces. Based on live poultry market (LPM) surveillance conducted by the Chinese provincial Health and Family Planning Commissions in December 2016, 9.4% of environmental samples were positive for A(H7N9) from LPMs in Guangdong and 15.8% of samples from LPMs in Jiangsu were positive for A(H7), of which most were positive for A(H7N9).

On human infections: Sudden increases in the number of human A(H7N9) cases reported during December and January have been observed in previous years. Compared to earlier waves of infection, further geographic spread of the virus was observed in this fifth wave. Of the cases where information on exposure history was known, as previous waves, most reported prior exposure to live poultry or potentially contaminated environments, including in LPMs.

Among cases reported in the fifth wave, three clusters were reported, comparable to findings in previous waves. Limited human-to-human transmission could not be ruled out in these clusters. So far, there has been no indication of significant changes in the epidemiology of the human infections reported, no evidence of sustained human-to-human transmission and no significant changes in the clinical presentation or disease outcome.

Read the entire analysis at World Health Organization

Based on information reported, UN officials conclude there is no evidence of sustained human-to-human transmission, and there are no significant changes in A(H7N9) virus properties or the epidemiology of human infections. As long as humans are exposed to infected animals and their environments, further human cases can be expected.