Hepatitis B

Hepatitis B is a liver infection caused by the hepatitis B virus (HBV). Most adults who are infected clear the virus within 6 months (acute infection). When the virus persists beyond 6 months, it becomes chronic hepatitis B — which can lead to cirrhosis, liver failure, and liver cancer over time. A safe, effective vaccine prevents hepatitis B.

Hepatitis B spreads through blood, semen, and other body fluids:

• Sexual contact (vaginal, anal, oral sex)
• Sharing needles, syringes, or drug equipment
• Mother to baby during birth
• Needlestick injuries or sharing personal items like razors or toothbrushes

HBV is much more infectious than HIV — it can survive outside the body for up to 7 days. It is not spread through casual contact, hugging, kissing, coughing, or sharing food.

Many people with acute hepatitis B have no symptoms. When symptoms appear (1–4 months after exposure):

• Fatigue and weakness
• Nausea, vomiting, loss of appetite
• Abdominal pain (upper right side)
• Dark urine, pale stools
• Joint pain
• Jaundice (yellowing of skin and eyes)

Chronic hepatitis B usually causes no symptoms for years — until significant liver damage has occurred.

A blood test checks for hepatitis B markers:

• HBsAg (surface antigen) — confirms active infection (window: 1–9 weeks)
• HBsAb (surface antibody) — indicates immunity from vaccine or past infection
• HBcAb (core antibody) — indicates past or current infection

The CDC recommends testing for all adults at least once, all pregnant people, and regular testing for people at higher risk. If positive, additional tests assess liver health and viral load.

Acute hepatitis B: supportive care (rest, fluids, avoid alcohol and liver-stressing medications). Most adults recover fully without specific antiviral treatment.

Chronic hepatitis B: antiviral medications (tenofovir, entecavir) suppress the virus and reduce risk of liver damage — but do not cure it. Regular monitoring of liver function is essential. Some people with chronic hepatitis B are eligible for interferon therapy. There is no cure, but treatment prevents progression to cirrhosis and liver cancer in most people.

Prevention options:

• Vaccine (3-dose series) — highly effective, recommended for all infants, children, and unvaccinated adults
• Post-exposure: hepatitis B immune globulin (HBIG) + vaccination within 24 hours of exposure
• Condoms reduce sexual transmission risk
• Don't share needles, syringes, razors, or toothbrushes
• Pregnant people should be tested — newborns of HBsAg-positive mothers need HBIG + vaccine at birth