Graphical Abstract (image) Cell Press Share Print E-Mail Caption The image shows a graphical abstract: H7N9 highly pathogenic avian influenza viruses emerged in China in 2017, prompting vaccination in poultry. Shi et al. examine H7N9 viruses across China before and after vaccination, revealing rapid evolution into subtypes and genotypes. Although vaccination reduced infections, some H7N9 and H7N2 viruses exhibit heightened virulence and expansion to ducks. Credit Chen et al. / Cell Host & Microbe 2018 Usage Restrictions Credit required Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.