Abstract: A method for detecting a drug-resistant virus, whose resistance is due to mutations in a viral protease which normally cleaves a substrate into at least two segments. The method comprises providing an electronic transducer having bound thereto a first binding molecule capable of specifically binding a first segment of the substrate and providing a second binding molecule capable of specifically binding a second segment of the substrate, the second binding molecule being capable of bringing about the precipitation of a precipitate on the electronic transducer. Detection of the presence or absence of the precipitate on the electronic transducer indicates the presence or absence of inhibitory activity of the drug. A screening method for potential viral drugs is also disclosed.