Biohazard virus. Computer artwork showing a virus (green) in a safe marked with a biohazard symbol (red). Viruses contain a core of genetic material, either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) surrounded by a protein coat, or capsid, and sometimes an outer glycoprotein envelope. The spikes on the surface recognise and bind to a host cell. Once inside, viruses hijack the cell's internal machinery to replicate themselves, before releasing themselves to infect further cells. Because of their infectious nature, viruses in the laboratory can pose a threat to human health and have to be kept secure to prevent them escaping.