Delayed 2009 Pandemic Influenza A Virus Subtype H1N1 Circulation in West Africa, May 2009–April 2010

Ndahwouh Talla Nzussouo, Jennifer Michalove, Ousmane M. Diop, Richard Njouom, Maria de Lourdes Monteiro, Herve Kadjo Adje, Serge Manoncourt, Joseph Amankwa, Lamine Koivogui, Samba Sow, Mohamed Brahim Elkory, Jean-Marc Collard, Ibrahim Dalhatu, Mbayame Ndiaye Niang, Kathryn Lafond, Filomena Moniz, Daouda Coulibaly, Karl C. Kronman, Buhari A. Oyofo, William Ampofo, Boubou Tamboura, Ahmed Ould Bara, Jean-Francois Jusot, Ekanem Ekanem, Fatoumata Diene Sarr, Inzune Hwang, Claire Cornelius, Babajide Coker, Stephen Lindstrom, Richard Davis, Erica Dueger, Ann Moen, and Marc-Alain Widdowson Influenza Division, U.S. Centers for Disease Control and Prevention, Influenza Division, Atlanta, Georgia; National Influenza Center, Institut Pasteur, Dakar, Senegal; National Influenza Center, Centre Pasteur Cameroon (CPC), Yaounde, Cameroon; Ministry of Health, Praia, Cape Verde; National Influenza Center, Institut Pasteur Cote d’Ivoire (IPCI), Abidjan, Cote d’Ivoire; Global Disease Detection and Response Program/US Naval Medical Research Unit No. 3, (NAMRU-3); Public Health Division, Ghana Health Services, Accra, Ghana; Laboratoire de Virologie PFHG, CHU Donka, Conakry, Guinee; Influenza Reference Laboratory, Centre National d’Appui a la Lutte Contre la Maladie (CNAM), Centre pour le Developpement des Vaccins du Mali (CVD), Bamako, Mali; Virology Laboratory, Institut National Recherche en Sante Publique (INRSP), Nouakchott, Mauritania; Influenza Reference Laboratory, Centre de Recherche Medicale et Sanitaire (CERMES), Niamey, Niger; Centers for Disease Control (CDC) Nigeria, Abuja, Nigeria; National Laboratory Network, Praia, Cape Verde; Institut National d’Hygiene Publique (INHP), Abidjan, Cote d’Ivoire; Naval Medical Research Unit No. 3 (NAMRU-3); National Influenza Center, Noguchi Memorial Institute for Medical Research (NMIMR), Accra, Ghana; and Federal Ministry of Health, Abuja, Nigeria