Hepatitis B virus. Coloured transmission electron micrograph (TEM) of hepatitis B viruses (circles), a cause of liver inflammation. The inflammation is the immune response to the virus that invades liver cells to replicate itself. The virus has a coat (capsid, pink/orange) bearing surface proteins (spikes, yellow), which the body detects as a foreign body (antigen). The complete virus is called a Dane particle and is approximately 42 nanometres in diameter. Hepatitis B is primarily transmitted by infected human blood, either in transfusions or on the shared needles of intravenous drug users. Magnification unknown.