Is another bird flu on the rise? Report from Nature on H7N9 type A influenza virus and reported outbreak in China.
Scientists and public health officials worldwide are on alert after China announced on 31 March that two people had died and a third had been seriously sickened from infections with a new avian flu virus, H7N9, that has never been seen before in humans.
There are numerous subtypes of flu, labelled with an H number, referring to the specific type of protein hemagglutinin and an N number, neuraminidase enzyme type. There are 17 H antigens (H1 to H17) and nine different N antigens (N1 to N9) and any combination might be possible. The newest H antigen type, identified as H17 by researchers, was isolated from fruit bats in 2012.