The present invention relates to a composition having antiviral activity for prophylaxis or treatment of flavivirus infection or a disease resulting therefrom in humans or animals, characterised in that the composition comprises quercetin, or analogues, or derivatives thereof. The composition may further comprise a pharmaceutically acceptable carrier. The antiviral activity may include inhibition of virus attachment to host cells and inhibition of intracellular virus replication. The flavivirus may comprise dengue virus type-1, dengue virus type-2, dengue virus type-3, and dengue virus type-4.
