False-colour transmission electron micrograph of two human coronaviruses. In humans, coronavirus causes the common cold & gastroenteritis; similar disease patterns occur in other animals. Coronaviruses are small spheres, 80-120 nanometres in diameter. Like all viruses, the coronavirus must infect a host cell in order to replicate. The nucleic acids contained in the head are injected into the host, where they instruct the host's genetic apparatus to synthesize the component parts of the virus. Once produced & reassembled, the virus bursts (lysis) out of the host cell, destroying it in the process. Magnification: x112,000 at 6x4.5cm size.