The invention relates to the use of Silvestrol, Episilvestrol and Silvestrol/Episilvestrol analoga/derivatives for treating infections with viruses whose protein translation requires a cap-structure at the 5-end of viral mRNAs, especially for treating infections with (-)RNA-strand viruses like the family of Filoviridae (Ebola- and Marburgvirus) as well as (+)RNA-strand viruses like the family of Coronaviridae (e.g. MERS and SARS).