The invention provides siRNA compositions that interfere with viral replication in respiratory viral infections, including respiratory syncytial virus and avian influenza A, including the H5N1 strain. The invention further provides uses of the siRNA compositions to inhibit expression of viral genes in respiratory virus-infected cells, and to uses in the treatment of respiratory virus infections in a subject. Generally the invention provides polynucleotide that includes a first nucleotide sequence of 15 to 30 bases that targets the genome of a respiratory syncytial virus or an influenza A virus, a complement thereof, a double stranded polynucleotide or a hairpin polynucleotide. Additionally the invention provides vectors, cells and pharmaceutical compositions containing siRNA sequences.