TY - JOUR AU - Morens, D M; Folkers, G K; Fauci, A S TI - What is a pandemic? JO - J Infect Dis. IS - 07 VL - 200 PY - 2009 DO - 10.1086/644537 L3 - PubMed-ID: 19712039 SP - 1018 EP - 1021 ER -