How is hepatitis B (HB) transmitted?

Hepatitis B Virus Transmission Routes

Hepatitis B virus (HBV) is primarily transmitted through percutaneous (puncture through skin) or mucosal exposure to infectious blood or body fluids containing blood, even in the absence of visible blood. 1

Primary Modes of Transmission

Blood-borne Transmission

• Percutaneous exposure is the most efficient mode of transmission 1
  • Injection drug use and sharing injection equipment 1
  • Needlestick injuries in healthcare settings 1
  • Contaminated medical or dental instruments 1
  • Unsafe injections in healthcare settings 1
  • Organ transplantation and dialysis procedures 1

Sexual Transmission

• HBV is efficiently transmitted through sexual contact 1
• Among adults in the United States, sexual contact is the most common source of HBV infection 1
• Risk factors for heterosexual transmission include:
  • Unprotected sex with an infected partner 1
  • Multiple sexual partners 1
  • History of other sexually transmitted infections 1
• Risk factors for transmission among men who have sex with men (MSM):
  • Multiple sex partners 1
  • History of other STIs 1
  • Anal intercourse 1

Perinatal (Mother-to-Child) Transmission

• Transmission from infected mothers to newborns during childbirth 1
• Risk varies based on maternal infection status:
  • 70-90% risk when mothers are both HBsAg and HBeAg positive 1
  • <10% risk when mothers are HBsAg positive but HBeAg negative 1
• Breastfeeding is not contraindicated for HBV-infected mothers 1

Household/Close Contact Transmission

• Sharing personal items with infected individuals 1
  • Toothbrushes 1
  • Razors 1
• Contact with exudates from dermatologic lesions 1
• Contact with HBsAg-contaminated surfaces 1
• HBV remains viable on environmental surfaces for at least 7 days 1

Infectious Body Fluids

• Blood contains the highest concentration of virus 1

• Semen and vaginal secretions are infectious 1

• Saliva has been demonstrated to be infectious 1

• Other potentially infectious fluids:

  • Cerebrospinal fluid 1
  • Synovial fluid 1
  • Pleural fluid 1
  • Peritoneal fluid 1
  • Pericardial fluid 1
  • Amniotic fluid 1

• Not efficient vehicles of transmission unless they contain blood:

  • Urine 1
  • Feces 1
  • Vomitus 1
  • Nasopharyngeal washings 1
  • Sputum 1
  • Sweat 1

Important Characteristics of HBV Transmission

• HBV is highly infectious and can be transmitted in the absence of visible blood 1
• The virus remains viable on environmental surfaces for at least 7 days 1
• HBV can be present on environmental surfaces at concentrations of 10²-10³ virions/mL even without visible blood 1
• Persons with chronic HBV infection are the major source of new infections 1
• All HBsAg-positive persons are infectious, but those with elevated HBV DNA or those with HBeAg are most infectious 1

Transmission in Special Settings

• Rare transmission in childcare settings 1
• No evidence of transmission by casual contact in the workplace 1
• Transmission from blood transfusion is now rare due to donor screening and viral inactivation procedures 1
• High rates of infection reported among unvaccinated residents of institutions for the mentally disabled 1

Prevention Strategies

• Universal vaccination of infants beginning at birth 1
• Routine vaccination of previously unvaccinated children and high-risk adults 1
• Screening of pregnant women and prophylaxis for infants born to infected mothers 1
• Safe injection practices and blood screening 2
• Safe sex practices and condom use 2
• Avoiding sharing personal items with infected individuals 2

Understanding these transmission routes is critical for implementing effective prevention strategies and reducing the burden of HBV infection worldwide.