Over the last weeks we have witnessed an epidemic of the so-called novel flu. This outbreak is no singular event; the recent years saw the emergence of new diseases such as SARS, AIDS, ESME and the return of old killers in new guises, such as Malaria, Tuberculosis, and, of course, Influenza. To combat these diseases we need to understand the dynamics of epidemic spreading. After a brief introduction to epidemic modeling, I will review some key insights that have been gained on epidemics spreading on networks, highlighting certain network properties that have a strong impact on epidemics and vaccination strategies. The focus on my talk will be on the effect of disease-induced changes of these network properties on the dynamics of the epidemics. Including the feedback loop between network topology and epidemic spreading in models gives rise to an adptive network exhibiting complex dynamical behaviour.