In regions of the world with the highest rates of hepatitis B, perinatal transmission (mother to child at birth) is the most common way that hepatitis B is spread. Horizontal transmission (exposure to infected blood), especially from an infected child to an uninfected child under the age of five years is also common.
Hepatitis B can also spread through needle stick injury, tattooing, piercing, sharing drug needles and syringes, and other exposures to infected blood, saliva, vaginal, and seminal fluids. Sexual transmission of hepatitis B can occur, with more common occurrences in men who have sex with men, heterosexuals with multiple sex partners, and sex workers (and their clients).
Hepatitis C is usually transmitted through exposure to blood from an infected individual. The most common way that HCV is transmitted is through sharing needles. Other potential sources of infection include at birth (~6% of infants of infected mothers), sexual intercourse (rare but more common in men who have sex with men), healthcare exposures, blood transfusions, and organ transplants (now very uncommon), unregulated tattoos or body piercings, and sharing personal items that have been in contact with infected blood (e.g. glucose monitors, razors).