Measles particle. The above image is 500 pixels across, the original measures 5000 pixels across.
MEASLES VIRUS (MeV) is a single stranded RNA (ssRNA) virus (Morbillivirus) causing the childhood disease measles with sometimes very severe sequelae subacute sclerosing panencephalitis. Measles virus particles occur in a range of sizes with the larger particles housing several genome copies (quite small particles can be complete enough to be infectious). The genome is ordered as a spiral that apparently lies in a somewhat disordered state within the virion, like a skein of rope, although some particles apparently display a more ordered arrangement. Surrounding the genome is a layer of matrix protein (shown in blue) which helps in particle assembly and orders the spikes. Around the matrix layer is the viral envelope acquired during budding from the host cell. The virion is covered with spikes (glycoproteins knobs) consisting of haemagglutinin and fusion proteins.