Influenza viruses are divided into three types, A, B, and C. Human influenza A and B viruses can cause seasonal epidemics, but influenza C causes only a mild respiratory illness. Influenza A virus can infect various host species. In 2013, human-infectious avian influenza A (H7N9) was first reported in China. By the second week of 2014, there were 210 laboratory-confirmed human cases in the country, and the mortality rate eventually reached 22
作者：Yingjie, Zhang；Qiqi, Liu；Dou, Wang；Suhong, Chen；Xiaobo, Wang；Shengqi, Wang
来源：SpringerPlus 2016 年 5卷 1期
