Hepatitis B Virus Transmission

Introduction

Hepatitis B virus (HBV) transmission can occur through various modes, including percutaneous exposure, sexual contact, and mother-to-child transmission, with vaccination being the most effective prevention strategy, as recommended by the Centers for Disease Control and Prevention (CDC) 1

HBV transmission can occur through injection drug use, needlestick injuries in healthcare settings, contaminated medical or dental instruments, unsafe injections, organ transplantation, and dialysis 1
The virus can be efficiently transmitted through sexual contact among both heterosexuals and men who have sex with men (MSM), with risk factors including unprotected sex, multiple sexual partners, and history of other sexually transmitted infections (STIs) 1, 2
HBV remains viable on environmental surfaces for at least 7 days and can be transmitted even when no visible blood is present, with a low infectious dose of 10^2-10^3 virions/mL 1, 3
The following table summarizes the modes of HBV transmission:

Mode of Transmission	Description
Percutaneous exposure	Injection drug use, needlestick injuries, contaminated medical instruments
Sexual contact	Unprotected sex, multiple sexual partners, history of other STIs
Mother-to-child transmission	During childbirth, particularly when mothers are HBsAg and HBeAg positive
Household contact transmission	Long-term close personal contact, sharing personal items, contact with HBsAg-contaminated surfaces
Bodily fluids	Blood, semen, vaginal secretions, saliva, cerebrospinal fluid, synovial fluid, amniotic fluid

HBV can be found in various body fluids, including blood, semen, vaginal secretions, saliva, and sweat, although the concentration of the virus varies 1
Breast milk can contain HBsAg, but transmission through breastfeeding is unlikely 1
Other potentially infectious fluids include cerebrospinal fluid, synovial fluid, and amniotic fluid, while urine, feces, and sweat are not efficient vehicles of transmission unless they contain blood 1

All HBsAg-positive persons are infectious, and those who are also HBeAg-positive are more infectious due to higher viral loads 1, 2, 3
HBV is approximately 100 times more infectious than HIV and 10 times more infectious than HCV, with high viral titers 4

The CDC recommends universal vaccination as the cornerstone of prevention, including all infants beginning at birth, previously unvaccinated children under 19 years, and adults at risk for HBV infection 1
Screening of pregnant women for HBsAg and HBV DNA testing for HBsAg-positive pregnant women is recommended, with maternal antiviral therapy and prophylaxis for infants born to HBsAg-positive women, including hepatitis B vaccine at birth and hepatitis B immune globulin (HBIG) 1
Effective prevention strategies include safe injection practices, blood screening, safe sex practices, and avoiding sharing of personal items with infected individuals 1

Breastfeeding is not contraindicated for HBV-positive mothers 1
Men who have sex with men, injection drug users, sexual partners of infected individuals, infants born to infected mothers, household contacts of infected persons, and healthcare workers are considered high-risk groups for HBV transmission 1
Not recognizing that all HBsAg-positive individuals are infectious, even without symptoms, can lead to missed opportunities for prevention 1
Delaying the birth dose of hepatitis B vaccine beyond 24 hours can reduce effectiveness, and assuming breastfeeding is contraindicated for HBV-positive mothers is a misconception, as HBsAg in breast milk is unlikely to lead to transmission 1, 3
The CDC states that HBV is not transmitted through casual contact in workplace settings, food or water, sharing eating utensils or drinking glasses, or hugging, kissing, holding hands, coughing, or sneezing 1, 5