Yes — hepatitis B is a sexually transmitted infection, and it's the most sexually transmissible of the three common blood-borne viruses (hepatitis B, hepatitis C, and HIV). The virus lives in blood, semen, and vaginal fluids, so unprotected vaginal, anal, and oral sex can all pass it. Unlike the other two, it's vaccine-preventable.
2020–2023, steady
many undiagnosed
protective for 20+ years
vs <5% in adults
| Item | Value |
|---|---|
| Acute cases | ~2,200/yr — 2020–2023, steady |
| Chronic infection | ~640,000+ — many undiagnosed |
| Vaccine | ~100% — protective for 20+ years |
| Infant chronicity | ~90% — vs <5% in adults |
The essentials: what hepatitis B is and why sex spreads it so well
Hepatitis B is a liver infection caused by the hepatitis B virus (HBV) CDC. It's mainly blood-borne and sexually transmitted, and it comes in two forms. Acute hepatitis B is the short-term illness in the first six months after exposure. Chronic hepatitis B lasts beyond six months and can be lifelong.
HBV stands out among sexually transmitted viruses because of how concentrated it is in body fluids and how durable it is. The virus is present in high amounts in semen and vaginal fluid, not just blood, so the same kinds of sexual contact that carry a low risk for hepatitis C carry a much higher risk for hepatitis B. It also survives on surfaces far longer than HIV. High viral load in genital fluids plus that toughness makes unprotected sex one of the leading routes of adult infection.
Age at infection decides almost everything about the outcome WHO. Caught in adulthood, hepatitis B becomes chronic in under 5% of people, and most adults clear the virus and develop lifelong immunity. Caught in infancy, it becomes lifelong in about 90%. A sexually acquired infection in an adult usually resolves, while the public-health stakes are highest for newborns.
Reported acute hepatitis B has held roughly steady at about 2,200 cases a year between 2020 and 2023 CDC surveillance. That number badly understates the burden. Hundreds of thousands more Americans live with chronic infection they don't know they have, because the virus is so often silent.
How hepatitis B spreads sexually vs. HCV and HIV
All three viruses are blood-borne, but they don't spread sexually at the same rate. The table below compares them on the points that matter for someone weighing sexual risk.
| Feature | Hepatitis B (HBV) | Hepatitis C (HCV) | HIV |
|---|---|---|---|
| Sexual transmissibility | High — most sexually transmissible of the three | Low (rises with blood contact, e.g. anal sex) | Moderate |
| Present in semen/vaginal fluid | Yes, high amounts | Low | Yes |
| Vaccine available | Yes | No | No |
| Outcome if caught as an adult | Usually cleared (chronic in under 5%) | Often becomes chronic | Lifelong without treatment |
| Curable | No (controllable) | Yes, with direct-acting antivirals | No (controllable) |
Symptoms of hepatitis B
Many people have no symptoms at all, which is why screening matters. When acute symptoms do appear, they reflect a liver under strain: fatigue, fever, poor appetite, nausea, abdominal pain (especially under the right ribs where the liver sits), joint pain, dark urine, clay-colored stools, and jaundice — a yellowing of the skin and the whites of the eyes caused by bilirubin building up when the liver can't process it.
Most people with chronic hepatitis B feel completely fine for years. Quiet damage accumulates without warning signs: scarring (cirrhosis) and a raised risk of liver cancer. For a fuller walk-through of what to watch for and how the timeline unfolds, see our guide to hepatitis b symptoms.
Testing: the panel that tells you where you stand
Hepatitis B is diagnosed with a triple serologic blood panel CDC. Each marker answers a different question: HBsAg (hepatitis B surface antigen) shows active infection, anti-HBs (surface antibody) shows immunity from recovery or vaccination, and total anti-HBc (core antibody) shows past or current infection. Read together, they tell a clinician whether you're susceptible, immune, or infected, and if infected, whether it's acute or chronic.
CDC now recommends that all adults aged 18 and older be screened for hepatitis B at least once in their lifetime, and that pregnant people be screened each pregnancy CDC, 2023. Universal screening replaced the older risk-based approach because so many infections are silent.
In practice, testing is straightforward: a simple blood draw, with results usually back in a few days, free or low-cost at health departments, Planned Parenthood, and Title X clinics. If you've had a possible exposure, timing matters. Antibodies and antigen take time to appear, so check our guide on when to test after exposure before you assume a negative result is final. When you're ready, you can get tested alongside a broader STI panel.
Treatment: controlled, not cured
Acute hepatitis B usually needs only supportive care — rest, fluids, and monitoring — because most adults clear it on their own. There's no antibiotic to take; the immune system does the work CDC STI guidelines.
Chronic hepatitis B is a different story. There's no cure, but FDA-approved antiviral medicines — tenofovir or entecavir — suppress the virus and protect the liver, cutting the long-term risk of liver cancer AASLD, 2018. Most people take these for life, since clearance happens in only about 2–5% even after a decade of treatment. Care is managed by a specialist who tracks viral load, liver enzymes, and liver health over time.
If you're prescribed antivirals, take them exactly as directed and don't stop when you feel well, because stopping abruptly can trigger a flare. Our overview of hepatitis b treatment covers what monitoring and long-term management look like.
Prevention: the vaccine changes everything
Vaccination is the single best protection, and it's what makes hepatitis B unique among sexually transmitted infections. ACIP recommends the hepatitis B vaccine for all adults aged 19–59, and for adults 60 and older who have risk factors CDC, 2022. The series produces protective antibodies in most people and provides durable, often lifelong immunity.
If you've already been exposed to someone who is HBsAg-positive, post-exposure prophylaxis is hepatitis B immune globulin (HBIG) plus the vaccine, given as soon as possible, ideally within 24 hours. HBIG supplies ready-made antibodies for immediate, short-term protection while the vaccine builds your own.
For everyday prevention, condoms used every time lower the risk of sexual transmission, and routine testing catches infections that have no symptoms. A diagnosis here is common and treatable. Clinics manage it daily, and it says nothing about you as a person.
Hepatitis B in pregnancy
Hepatitis B can pass from a pregnant person to the baby around the time of birth, the most common way young children become infected, so every pregnancy is screened for HBsAg CDC. An infant infected at birth has about a 90% chance of developing lifelong hepatitis B, far higher than the roughly 5% of adults who don't clear it.
This is one of the most preventable outcomes in medicine. Every newborn gets the hepatitis B vaccine at birth, and a baby born to an HBsAg-positive parent also gets HBIG, both within 12 hours of birth. That combination drops transmission to about 3.6%, versus 11.6% with vaccine alone, and adding an antiviral for high-viral-load mothers lowers it further to under 2% perinatal HBV meta-analysis. Our guide to hepatitis and pregnancy explains the full protocol.
When to see a clinician
See a clinician if you've had a possible exposure (unprotected sex with a new or untested partner, a needlestick, or shared injection equipment), if you develop jaundice or dark urine, or if you're pregnant and haven't been screened. Don't wait for symptoms, since the most consequential infections are the silent ones. If exposure was recent, ask specifically about post-exposure prophylaxis, which only works within a narrow window.