Influenza is a severe, febrile disease of the airways that occurs epidemically in the winter months. It is caused by influenza viruses. In cycles of about 30 years, these seasonal epidemics progress to pandemics with high numbers of infections and deaths worldwide. In order to prevent just this situation, so-called pandemic plans have been developed worldwide. Besides vaccination, general hygienic precautions and antiviral therapies are the most important measures in the management of influenza. We can only wait and see whether or not the newly appeared H1N1 variant of the influenza virus A (Mexican flu, swine flu) will actually turn out to be a new worldwide pandemic.