Hepatitis B belongs to the national statutory class B infectious disease, it is mainly through the blood, but also exists in the semen, menstruation, vaginal secretions, saliva, breast milk, tears, urine, sweat and other bodily fluids of hepatitis B patients, so intimate contact also has some contagious. But its contagiousness is not as terrible as some people imagine, as if a contact immediately be infected, so there is no need to be overly fearful, first of all, we need to find out what kind of people have strong contagious, one is acute hepatitis B or chronic hepatitis in the acute phase of the strong contagious; two is “two to half” in the laboratory test was The third is the “two to half” test is “small three positive”, but the HBVDNA virus titer is high, the infectiousness is certainly strong; fourth is the “two to half” test is “small three positive”, but the HBVDNA virus titer is high, the infectiousness is certainly strong; fourth is the “two to half” test is “small three positive”, but the HBVDNA virus titer is high. “If one of the two has a high titer, it means that it is infectious; fifth, the single anti-HBc positive person decides its infectiousness according to the titer. Sixth, 2, 4, 5 three positive at the same time, may be infectious or non-infectious, need to determine the HBVDNA titer, such as high titer is infectious.