Hepatitis is a viral infection that affects the liver. There are three main types. Hepatitis A is caught through poor hygiene and infected food and water. Hepatitis B and C are both easily transmitted through blood (although B is also found in semen and saliva) and have become problems for people who share injecting equipment when using drugs. They are easier to pass from other person to another than the virus that leads to AIDS. People may have no symptoms of hepatitis when they first get infected, but can still infect others if they share injecting equipment. They might become quite ill, possibly years later, and feel very tired and get flu-like symptoms, vomiting, fever and jaundice. There is a vaccine to protect against hepatitis B, and one is being developed in France for hepatitis C. To make sure they do not get hepatitis, injecting drug users (IDUs) are advised never to share injecting equipment with anyone else and to use syringe exchange schemes.