Avian influenza strain H7N9 was first diagnosed during March 2013 in China with patients having contracted the infection in live-bird markets. In response, public health officials in metropolitan areas introduced a surveillance program for live poultry offered for sale and wet markets were closed temporarily in areas where cases occurred. In January 2017, China launched an H7N9 vaccination program in Guangxi and Guangdong Provinces with extension of the program to other areas. A bivalent H5/H7 vaccine was deployed nationwide replacing an existing H5N1 product. A benefit-cost analysis of the vaccination program confirmed a positive value of 18.6 with a net present value of $250 million*. Total costs of the vaccination program over the three-years of review amounted to $14 million confirming the value of mass vaccination in the context of a nation consuming a high proportion of chicken purchased at live bird markets.
In 2014 avian influenza H5N6 emerged among consumers of poultry with 63 cases reported over seven years. Four cases have been diagnosed since 2021 with two fatalities. It is considered significant that close contact between the patients and their direct cohabitants did not result in secondary infection, suggesting that H5N6 is not transmissible among humans. Infection probably occurs following close contact with the viscera of viremic chickens or with aerosols in wet markets affecting humans with susceptibility due to a genetic predisposing factor.
*Tang, H. et al. Benefit-cost analysis of an H7N9 vaccination program in poultry in Guangxi, China. Preventive Veterinary Medicine. doi.org/10.1016/j.prevetmed.2022.105580