Flu

The disease commonly known as the flu (medical influenza) refers to an infection by an influenza virus. Influenza viruses are divided into influenza A, B, and C. A and B are responsible for the seasonal waves of influenza (influenza epidemic) each year. While some animals also contract influenza A and C, influenza B has been found primarily in humans. New strains of the virus are constantly emerging. People are vulnerable to these strains even if they have already had a flu infection or vaccination in the past. New strains are caused by mutation of the virus and transmission of influenza viruses between animals and humans (e.g. swine flu or bird flu). Vaccines must therefore be developed every year to combat newly emerging influenza viruses. The Standing Commission on Vaccination (STIKO) recommends that certain risk groups be re-vaccinated every year.