Hepatitis B virus (HBV), causes hepatitis characterized with a long incubation period, which is transmitted through bodily fluids and affects the liver. Ten percent of people contaminated with HBV are carriers of this disease and their blood is infected during months, years, or even their whole life. Seventy percent of ill people develop a chronic form of the disease, but they do not appear sick. The other thirty percent continuously suffer from a liver disease, which can became cirrhosis of the liver and, after 30 or 40 years, liver cancer. Virus diameter : 42 nm. Transmission electron micrograph (TEM) with HDRI treatments.