Hepatitis B comes from a virus (the hepatitis B virus, or HBV) that infects the liver and is spread mainly through blood and certain body fluids like semen and vaginal fluids. Scientists know HBV has been circulating in humans for thousands of years, but the exact original animal or first human source is still not fully proven, though genetic studies suggest very ancient roots in regions such as North Africa and the Middle East.

What hepatitis B is

  • Hepatitis B is a viral infection that attacks liver cells and can cause both short-term (acute) and long-term (chronic) disease.
  • The virus is a small DNA virus in the Hepadnaviridae family that travels in the bloodstream and primarily replicates in the liver.

Where it originally comes from

  • Ancient DNA from human remains shows hepatitis B has infected people for at least 10,000 years in different parts of the world, including Eurasia and the Americas.
  • Modern evolutionary studies suggest hepatitis B likely arose as a prehistoric virus, with some major genetic lineages (genotypes A and D) tracing back to North Africa and the Middle East before spreading globally.

How people get hepatitis B today

  • The virus is transmitted through contact with infected blood or body fluids, especially blood, semen, and vaginal secretions.
  • Common modern routes include:
    • From mother to baby during childbirth
    • Unprotected sex with an infected partner
    • Sharing needles or syringes for drugs, tattoos, or piercings
    • Contact with infected blood in healthcare or through shared items like razors or toothbrushes that may have blood on them

Why it is still a big issue

  • Hundreds of millions of people worldwide live with chronic hepatitis B infection, and many are infected in infancy or early childhood in high-burden regions.
  • Chronic infection can lead to serious problems like liver cirrhosis and liver cancer, which is why vaccination and early testing are so important.

In simple terms: hepatitis B “comes from” a very old liver virus that became adapted to humans long ago, and today it spreads mainly through blood, sex, and from mother to baby rather than from the environment or casual contact.

Information gathered from public forums or data available on the internet and portrayed here.