Corona viruses. Coloured transmission electron micrograph of a section through a cluster of corona viruses. The corona viruses cause the common cold, gastroenteritis, pneumonia and acute renal failure in humans. The corona virus received its name because of its characteristic "setting sun" appearance. This is provided by the projections (peplomers) studding the outer membrane of the virus. Beneath the outer membrane of each virus is the protein shell called the capsid. This encloses the nucleoprotein (genetic material)