Hepatitis B spreads through blood and body fluids
Hepatitis B is transmitted when blood or certain body fluids from an infected person enter another person's bloodstream or through breaks in the skin or mucous membranes. The virus does not spread through saliva, so you cannot catch it by sharing food, drinks, or utensils. It also does not spread through coughing, sneezing, hugging, or touching someone's skin.
The virus lives in the blood and some body fluids of infected people. If those fluids reach your blood—through a cut, needle stick, or mucous membrane—transmission can occur. This is why certain activities and situations carry risk while others do not.
Key Takeaways
- Hepatitis B spreads through blood-to-blood contact and sexual contact, not through casual contact like sharing meals or shaking hands.
- Unprotected sex with an infected partner, sharing needles, and needle stick injuries are the most common ways adults acquire hepatitis B.
- Infants born to infected mothers can contract the virus during delivery, but preventive treatment given at birth stops this transmission in most cases.
- A hepatitis B vaccine prevents infection and is part of routine childhood immunizations in most countries.
Sexual contact and hepatitis B transmission
Hepatitis B spreads during unprotected sex because the virus can enter through tiny tears in the genital tissue or through the mucous membranes of the rectum, urethra, or vagina. The risk exists whether the infected partner is male or female. Using condoms or dental dams during sex significantly reduces transmission risk.
People with hepatitis B can have sex safely if their partner is vaccinated or if they use barrier protection consistently. If you are in a sexual relationship with someone who has hepatitis B, talk to your doctor about vaccination and testing to know your own status.
Blood exposure and needle-related transmission
Sharing needles or syringes—whether for injected drugs, steroids, or any other substance—is a direct blood-to-blood route for hepatitis B. A single needle can carry enough virus to transmit infection. Healthcare workers can also contract hepatitis B through needle stick injuries or cuts during patient care, though this risk is lower with modern safety equipment.
Tattoos and body piercings done with non-sterile needles or equipment have transmitted hepatitis B. If you are considering a tattoo or piercing, choose a licensed facility that follows strict sterilization protocols and can show you their equipment is properly cleaned and sterilized between clients.
Mother-to-child transmission during pregnancy and birth
An infected mother can pass hepatitis B to her baby during pregnancy or at delivery. The risk is highest during the birth process, when the baby may be exposed to the mother's blood. Infants born to mothers with hepatitis B receive a vaccine and an injection of hepatitis B immunoglobulin (a protective antibody) within hours of birth. This treatment prevents infection in approximately 95 percent of cases.
Pregnant people with hepatitis B should inform their healthcare provider so that preventive measures can be arranged before delivery. Breastfeeding is safe and does not transmit hepatitis B, even if the mother is infected.
Sharing personal items and household transmission
Hepatitis B does not spread through sharing toothbrushes, razors, or eating utensils under normal circumstances. However, if a toothbrush or razor causes bleeding in the mouth or on the skin, and the infected person also has bleeding gums or cuts, there is a theoretical risk. In practice, this route is uncommon.
People with hepatitis B can live safely with family members who are vaccinated or who do not have the virus. Standard household hygiene—washing hands, not sharing personal care items, and cleaning surfaces with soap and water—is sufficient. Hepatitis B virus dies quickly outside the body and cannot survive on intact skin.
Blood transfusions and organ transplants
In countries with rigorous blood screening programs, hepatitis B transmission through transfusion is extremely rare because all donated blood is tested for the virus. Organ transplants from infected donors can transmit hepatitis B, but transplant centers screen donors and inform recipients of any known infection so they can receive preventive treatment.
If you received a blood transfusion or organ transplant before widespread screening began (in most developed countries, this was the 1980s or earlier), ask your doctor about hepatitis B testing. People who received transfusions before screening was routine may have been exposed.
Who is at higher risk of hepatitis B
Certain groups have higher exposure risk: people who inject drugs, healthcare workers, people with multiple sexual partners or a partner with hepatitis B, and people born in countries where hepatitis B is more common. Infants born to infected mothers are also at higher risk without preventive treatment.
If you fall into any of these groups, talk to your doctor about hepatitis B testing and vaccination. Testing can show whether you have been infected in the past or are currently infected. Vaccination can prevent infection if you have not been exposed yet.
Frequently Asked Questions
Can I catch hepatitis B from a mosquito bite or insect sting?
No. Hepatitis B does not spread through insect bites. The virus requires direct entry into the bloodstream through blood-to-blood contact, sexual contact, or mucous membrane exposure. Insects do not transmit it.
If someone with hepatitis B prepares my food, can I get infected?
No. Hepatitis B virus cannot survive in the stomach and does not spread through food or saliva. You can safely eat food prepared by someone with hepatitis B as long as they follow normal food safety practices like handwashing.
What should I do if I think I was exposed to hepatitis B?
Contact your doctor or an urgent care clinic as soon as possible. If exposure occurred within 24 hours, post-exposure prophylaxis (a combination of vaccine and immunoglobulin) may prevent infection. Your doctor will also order a test to check your current hepatitis B status and discuss next steps based on your vaccination history.
Is hepatitis B transmitted through sweat or tears?
No. Hepatitis B virus is not present in sweat or tears in amounts that can cause infection. You cannot catch hepatitis B from sharing a gym towel, swimming pool, or by touching someone who is sweating.
Can I donate blood if I have hepatitis B?
No. People with hepatitis B cannot donate blood, plasma, organs, or tissue because the virus could be transmitted to the recipient. Blood banks screen all donations for hepatitis B, and infected individuals are permanently deferred from donating.