Antiviral drugs usually target an individual, precisely-defined structure. The influenza drug Tamiflu, for example, has a very particular binding site on the virus. It only works, however, at an early stage. Therapy strategies that also work at a later stage are desperately being sought. Especially drugs that could prevent viruses from attaching themselves to, invading and multiplying in host cells would be most welcome when it comes to influenza and many other virus infections.