Budding measles viruses. Coloured Scanning Electron Micrograph (SEM) of blue-coloured measles viruses (morbillivirus group) budding off the surface of an infected cell (green). These viruses consist of a lipid-protein envelope that surrounds a protein-capsid containing RNA-genetic material. The envelope is actually part of the infected cell's membrane through which the virus has budded. Measles is very infectious and mainly affects children, producing fever and rash. One attack usually gives life-long immunity. Magnification: x17,000 at 6x7cm size. Magnification: x40,000 at 8x10 inch size.