Hepatitis B is usually contagious in either state, but the degree of contagiousness varies. Hepatitis B is caused by the hepatitis B virus and is contagious, mainly through blood transmission, mother-to-child transmission, close contact transmission, and medical transmission. The size of hepatitis B infectiousness is determined by the value of hepatitis B viral load, the higher the value, the more infectious it usually is, while the lower the value, the less infectious it is. For people in close contact with hepatitis B patients, they need to be tested for hepatitis B surface antibodies to determine whether they have protective antibodies and whether they are vaccinated against hepatitis B for self-protection, and they also need to pay close attention to it in their lives.