title: Timing of influenza epidemics and vaccines in the American tropics, 2002-2008, 2011-2014.
abstract: BACKGROUND
  Influenza-associated illness results in increased morbidity and mortality in the Americas. These effects can be mitigated with an appropriately chosen and timed influenza vaccination campaign. To provide guidance in choosing the most suitable vaccine formulation and timing of administration, it is necessary to understand the timing of influenza seasonal epidemics.
  
  
  OBJECTIVE
  Our main objective was to determine whether influenza occurs in seasonal patterns in the American tropics and when these patterns occurred.
  
  
  METHODS
  Publicly available, monthly seasonal influenza data from the Pan American Health Organization and WHO, from countries in the American tropics, were obtained during 2002-2008 and 2011-2014 (excluding unseasonal pandemic activity during 2009-2010). For each country, we calculated the monthly proportion of samples that tested positive for influenza. We applied the monthly proportion data to a logistic regression model for each country.
  
  
  RESULTS
  We analyzed 2002-2008 and 2011-2014 influenza surveillance data from the American tropics and identified 13 (81%) of 16 countries with influenza epidemics that, on average, started during May and lasted 4 months.
  
  
  CONCLUSIONS
  The majority of countries in the American tropics have seasonal epidemics that start in May. Officials in these countries should consider the impact of vaccinating persons during April with the Southern Hemisphere formulation.
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Lizette Olga
authors.identifier: http://orcid.org/0000-0002-3520-0702
authors.initials: LO
authors.lastname: Durand
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Po-Yung
authors.initials: PY
authors.lastname: Cheng
authors.affiliation: Pan American Health Organization, Washington, DC, USA.
authors.forename: Rakhee
authors.initials: R
authors.lastname: Palekar
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Wilfrido
authors.initials: W
authors.lastname: Clara
authors.affiliation: Universidad del Valle de Guatemala, Guatemala City, Guatemala.
authors.forename: Jorge
authors.initials: J
authors.lastname: Jara
authors.affiliation: Pan American Health Organization, Washington, DC, USA.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Cerpa
authors.affiliation: Pan American Health Organization, Washington, DC, USA.
authors.forename: Nathalie
authors.initials: N
authors.lastname: El Omeiri
authors.affiliation: Pan American Health Organization, Washington, DC, USA.
authors.forename: Alba Maria
authors.initials: AM
authors.lastname: Ropero-Alvarez
authors.affiliation: Centro Nacional de Influenza, Laboratorio de Virología, Instituto Nacional De Salud, Bogotá, Colombia.
authors.forename: Juliana Barbosa
authors.initials: JB
authors.lastname: Ramirez
authors.affiliation: Centro Nacional de Influenza, Centro Nacional de Referencia de Virología, Instituto Costarricense de Investigación y Enseñanza en Nutrición y Salud, San Jose, Costa Rica.
authors.forename: Jenny Lara
authors.initials: JL
authors.lastname: Araya
authors.affiliation: Centro Nacional de Influenza, Departamento de Virología, Instituto de Medicina Tropical ‟Pedro Kouríˮ, Havana, Cuba.
authors.forename: Belsy
authors.initials: B
authors.lastname: Acosta
authors.affiliation: El Centro de Referencia Nacional de Influenza y Otros Virus Respiratorios Insituto Nacional de Investigacion en Salud Publica (INSPI), Quito, Ecuador.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Bruno
authors.affiliation: Unidad de Vigilancia Laboratorial Dr. Max Bloch, Centro Nacional de Influenza, San Salvador, El Salvador.
authors.forename: Celina
authors.initials: C
authors.lastname: Calderon de Lozano
authors.affiliation: Centro Nacional de Influenza, Laboratorio Nacional de Salud, Ciudad de Guatemala, Guatemala City, Guatemala.
authors.forename: Leticia Del Carmen
authors.initials: Ldel C
authors.lastname: Castillo Signor
authors.affiliation: Departamento de Laboratorio Nacional de Vigilancia de la Salud, Tegucigalpa, Honduras.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Matute
authors.affiliation: National Influenza Centre-Jamaica, Department of Microbiology, University of West Indies, Kingston, Jamaica.
authors.forename: Sandra
authors.initials: S
authors.lastname: Jackson-Betty
authors.affiliation: PAHO/WHO Jamaica, National Influenza Centre-Jamaica, Department of Microbiology, University of West Indies, Kingston, Jamaica.
authors.forename: Kam Suan
authors.initials: KS
authors.lastname: Mung
authors.affiliation: National Influenza Centre, Instituto de Diagnóstico y Referencia Epidemiológicos (InDRE), Ministry of Health, Mexico City, Mexico.
authors.forename: José Alberto
authors.initials: JA
authors.lastname: Díaz-Quiñonez
authors.affiliation: National Influenza Centre, Instituto de Diagnóstico y Referencia Epidemiológicos (InDRE), Ministry of Health, Mexico City, Mexico.
authors.forename: Irma
authors.initials: I
authors.lastname: López-Martinez
authors.affiliation: Laboratorio Nacional de Virología, Centro Nacional de Diagnóstico y Referencia, Ministry of Health, Managua, Nicaragua.
authors.forename: Angel
authors.initials: A
authors.lastname: Balmaseda
authors.affiliation: Depto. de Investigación en Virología Instituto Conmemorativo Gorgas, Panamá City, Panamá
authors.forename: Brechla Morneo
authors.initials: BM
authors.lastname: Arévalo
authors.affiliation: Laboratorio Central de Salud Pública, Asunción, Paraguay.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Vazquez
authors.affiliation: Instituto Nacional de Salud, Lima, Peru.
authors.forename: Victoria
authors.initials: V
authors.lastname: Gutierrez
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Garten
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Marc-Alain
authors.initials: MA
authors.lastname: Widdowson
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Azziz-Baumgartner
mesh_terms: D001938:Brazil / Q000453:epidemiology; D062665:Epidemiological Monitoring; D006801:Humans; D007252:Influenza Vaccines / Q000737:chemistry; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control* / Q000821:virology; D009527:Nicaragua / Q000453:epidemiology; D058873:Pandemics / Q000517:prevention & control / Q000706:statistics & numerical data*; D010568:Peru / Q000453:epidemiology; D011159:Population Surveillance; D012621:Seasons; D013997:Time Factors; D014329:Tropical Climate; D014481:United States / Q000453:epidemiology; D014611:Vaccination
chemical_list: D007252:Influenza Vaccines
keywords: Influenza; surveillence; vaccine