An avian influenza virus that emerged in 2013 is suddenly spreading widely in China, causing a sharp spike in human infections and deaths. Last month alone it sickened 192 people, killing 79, according to an announcement this week by China’s National Health and Family Planning Commission in Beijing. The surge in human cases is cause for alarm, says Guan Yi, an expert in emerging viral diseases at the University of Hong Kong in China. “We are facing the largest

pandemic threat in the last 100 years,” he says. As of 16 January, the cumulative toll from H7N9 was 918 laboratory-confirmed human infections and 359 deaths, according to the World Health Organization (WHO). Despite its high mortality rate, H7N9 had gotten less attention of late than two other new strains—H5N8 and H5N6—that have spread swiftly, killing or forcing authorities to cull millions of poultry. READ MORE