The present invention relates to a method for preventing transmission of influenza, wherein said method comprises administering an effective amount of a compound to a patient having an influenza virus infection, herein referred to as "index patient", wherein the compound has one of the formulae (I) and (II), or its pharmaceutically acceptable salt. The compound to be used in the present invention reduces infectivity of the influenza virus of the index patient, and therefore, reduces the risk of the index patient to trigger an influenza epidemic or an influenza pandemic as compared to a control patient. Therefore, one aspect of the present invention relates to a method for preventing an influenza epidemic or an influenza pandemic, wherein the method comprises administering an effective amount of a compound to patients having an influenza virus infection (index patients), wherein the compound is administered to at least 10% of all influenza infected persons of a city's or country's population, and wherein the compound has one of the formulae (I) and (II), or is a pharmaceutically acceptable salt thereof.
