The motto of this year’s World Hepatitis Day, proclaimed annually on 28 July by the World Health Organisation (WHO), is “It’s time to act“. Hundreds of millions of people worldwide are affected by chronic viral hepatitis, which can lead to severe liver disease and cancer. The five main types of hepatitis viruses infecting humans—A, B, C, D and E—together are responsible for 1.3 million deaths and 2.2 million new infections per year. Of these, the hepatitis B virus causes most cases of persistent infections and deaths.