Influenza A virus. Coloured Transmission Electron Micrograph (TEM) of a cluster of influenza (flu) type A viruses. Influenza A is a contagious ortho- myxovirus, more virulent than influenza type B. At centre the viruses (blue) appear rounded but their shape is variable. Tiny spikes on the protein coat of the viruses are seen. These spikes stick to host cells when the virus invades the body. The virus has an affinity for mucus, and is spread in droplets from coughs or sneezes. Influenza symptoms include fever, chills and headache. The virus spikes may change structure to create new influenza strains that can spread as an epidemic. Magnification: x90,000 at 6x7cm size.