What are the ways to contract Hepatitis B (HBV)?

Ways to Contract Hepatitis B

Hepatitis B is transmitted through percutaneous, mucosal, or nonintact skin exposure to infectious blood or body fluids, with the primary routes in adults being sexual contact and blood exposure through injection drug use. 1

Primary Transmission Routes

Sexual Transmission

• Sexual contact accounts for approximately 63% of new HBV infections among adults in the United States, with 39% from heterosexual transmission and 24% among men who have sex with men (MSM). 2
• HBV is transmitted efficiently through both heterosexual and homosexual contact, with semen and vaginal secretions being highly infectious. 1
• Risk factors for heterosexual transmission include unprotected sex with an infected partner, multiple sex partners, and history of other sexually transmitted infections. 1
• For MSM, risk factors include multiple sex partners, history of other STIs, and anal intercourse. 1

Blood Exposure

• Blood exposure through injection drug use is the most efficient mode of transmission, accounting for 25-50% of all hepatitis B cases in industrialized countries. 1, 3
• Percutaneous transmission occurs through sharing needles, injection-preparation equipment, and other drug paraphernalia. 1
• Healthcare workers face risk through needlestick injuries and exposure to contaminated medical equipment. 1, 3

Perinatal Transmission

• Mother-to-infant transmission carries a 70-90% risk of chronic infection when the mother is both HBsAg and HBeAg positive without prophylaxis. 3
• This is the dominant route of transmission globally, though less common in the United States due to universal screening and prophylaxis programs. 3

Infectious Body Fluids

Highly Infectious Fluids

• Blood contains the highest viral concentration and is the most infectious body fluid. 3
• Semen, vaginal secretions, and saliva are highly infectious and can transmit HBV. 1, 3

Potentially Infectious Fluids

• Cerebrospinal fluid, synovial fluid, pleural fluid, peritoneal fluid, pericardial fluid, amniotic fluid, tears, and bile can also transmit the virus. 1, 3

Non-Infectious or Low-Risk Fluids

• Urine, feces, vomitus, nasopharyngeal washings, sputum, and sweat are not efficient vehicles of transmission unless they contain blood. 1
• Breast milk is unlikely to transmit HBV, and breastfeeding is NOT contraindicated for HBsAg-positive mothers. 1, 3

Household and Interpersonal Contact

• Transmission occurs through sharing personal items that may contact blood, such as toothbrushes or razors. 1, 3, 4
• Contact with exudates from dermatologic lesions or open skin lesions can transmit HBV. 1, 3
• Transmission rates to susceptible household contacts range from 14-60%. 3
• Person-to-person transmission can occur in settings involving nonsexual interpersonal contact over extended periods, such as among household contacts of chronically infected persons. 1

Environmental Persistence

• HBV remains infectious on environmental surfaces for at least 7 days at room temperature. 1, 3
• HBV can be transmitted in the absence of visible blood, with HBV DNA concentrations as low as 10²-10³ IU/mL on surfaces still capable of causing transmission. 1
• Contact with HBsAg-contaminated surfaces in settings like schools, child care centers, and facilities for developmentally disabled persons can transmit infection. 1, 3

Healthcare and Other Settings

• Contaminated medical or dental instruments can transmit HBV when proper sterilization procedures are not followed. 1
• Unsafe injections, including therapeutic injections with contaminated equipment, have caused outbreaks. 1
• Organ transplantation and dialysis can transmit HBV, though screening has reduced this risk. 1, 3
• Blood transfusion is now rare as a transmission route due to donor screening and viral inactivation procedures. 1, 3
• Tattooing and acupuncture with contaminated equipment can transmit HBV. 1

Critical Clinical Considerations

Infectivity Levels

• All HBsAg-positive persons are infectious, but those who are also HBeAg-positive are most infectious, with blood containing HBV DNA levels of 10⁷-10⁹ IU/mL. 1
• Persons with occult HBV infection (HBsAg-negative but HBV DNA-positive) can still transmit infection, though this is less common. 1, 3

Prevention Counseling

• HBV does not stop spreading to others through sex, sharing needles, or blood exposure even with treatment. 5, 4
• Safe sexual practices, never sharing needles, and avoiding sharing personal items that can have blood or body fluids are essential prevention measures. 5, 4
• A vaccine is available to protect people at risk from becoming infected with HBV, and vaccination is recommended for all adults at risk. 2, 5, 4