K e y M e s s a g e s 1. A differential induction of autophagy was noted between influenza virus A/Hong Kong/54/98 (H1N1) and A/Quail/Hong Kong/G1/97 (H9N2/ G1) infections. 2. The H9N2/G1 virus, which shows a delay in apoptosis activation, induces autophagy to a greater extent than the H1N1 virus. 3. Autophagy is not involved in H9N2/G1 virus replication in primary human blood macrophages. 4. Using 3-methyladenine to inhibit autophagy and small interfering RNA to silence the autophagy gene (Atg5), autophagic responses play a role in influenza virus-induced CXCL10 and interferon-