Hepatitis B Virus
Transmission: Hepatitis B virus (HBV) is spread by direct contact with blood or body fluids of any infected person. This can occur during unprotected sexual contact, blood transfusions, sharing of contaminated needles and syringes, or vertical transmission from mother to child during childbirth. The newborn will most likely not show any symptoms if infected, but has a 90% chance of developing a chronic infection.
This virus is particularly lethal because only a minute amount (0.0001mL) of the virus is required to cause infection. Contact via the lips could also cause the spread of the virus, especially if the infected person has a cut on their lip. However, the virus is not shed in the saliva.