A model of the H1N1 virus, which causes ‘swine flu’. The name H1N1 refers to the types of haemagglutinin and neuraminidase proteins on the surface of the virus. There are roughly ten times as many haemagglutinin proteins (red) as neuraminidase (yellow). In the centre is the single-stranded viral RNA (purple).
Anna Tanczos/Wellcome Images
