title: Polio outbreak investigation and response in Somalia, 2013.
abstract: BACKGROUND
  For >2 decades, conflicts and recurrent natural disasters have maintained Somalia in a chronic humanitarian crisis. For nearly 5 years, 1 million children <10 years have not had access to lifesaving health services, including vaccination, resulting in the accumulation by 2012 of the largest geographically concentrated cohort of unvaccinated children in the world. This article reviews the epidemiology, risk, and program response to what is now known as the 2013 wild poliovirus (WPV) outbreak in Somalia and highlights the challenges that the program will face in making Somalia free of polio once again.
  
  
  METHODS
  A case of acute flaccid paralysis (AFP) was defined as a child <15 years of age with sudden onset of fever and paralysis. Polio cases were defined as AFP cases with stool specimens positive for WPV.
  
  
  RESULTS
  From 9 May to 31 December 2013, 189 cases of WPV type 1 (WPV1) were reported from 46 districts of Somalia; 42% were from Banadir region (Mogadishu), 60% were males, and 93% were <5 years of age. All Somalian polio cases belonged to cluster N5A, which is known to have been circulating in northern Nigeria since 2011. In response to the outbreak, 8 supplementary immunization activities were conducted with oral polio vaccine (OPV; trivalent OPV was used initially, followed subsequently by bivalent OPV) targeting various age groups, including children aged <5 years, children aged <10 years, and individuals of any age.
  
  
  CONCLUSIONS
  The current polio outbreak erupted after a polio-free period of >6 years (the last case was reported in March 2007). Somalia interrupted indigenous WPV transmission in 2002, was removed from the list of polio-endemic countries a year later, and has since demonstrated its ability to control polio outbreaks resulting from importation. This outbreak reiterates that the threat of large polio outbreaks resulting from WPV importation will remain constant unless polio transmission is interrupted in the remaining polio-endemic countries.
authors.affiliation: Somalia Liaison, World Health Organization.
authors.forename: Raoul
authors.initials: R
authors.lastname: Kamadjeu
authors.affiliation: Global Immunization Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Abdirahman
authors.initials: A
authors.lastname: Mahamud
authors.affiliation: Global Immunization Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Jenna
authors.initials: J
authors.lastname: Webeck
authors.affiliation: United Nations Children's Fund Somalia, Nairobi, Kenya.
authors.forename: Marie Therese
authors.initials: MT
authors.lastname: Baranyikwa
authors.affiliation: United Nations Children's Fund Somalia, Nairobi, Kenya.
authors.forename: Anirban
authors.initials: A
authors.lastname: Chatterjee
authors.affiliation: Health Directorate, Somalia Ministry of Human Development and Public Services, Mogadishu.
authors.forename: Yassin Nur
authors.initials: YN
authors.lastname: Bile
authors.affiliation: Global Immunization Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Julianne
authors.initials: J
authors.lastname: Birungi
authors.affiliation: Global Immunization Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Chukwuma
authors.initials: C
authors.lastname: Mbaeyi
authors.affiliation: Somalia Liaison, World Health Organization.
authors.forename: Abraham
authors.initials: A
authors.lastname: Mulugeta
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003140:Communicable Disease Control / Q000379:methods*; D004196:Disease Outbreaks; D005243:Feces / Q000821:virology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D011051:Poliomyelitis / Q000453:epidemiology* / Q000517:prevention & control*; D017955:Poliovirus / Q000302:isolation & purification*; D018570:Risk Assessment; D012307:Risk Factors; D012998:Somalia / Q000453:epidemiology
keywords: Somalia; horn of Africa; outbreak; poliomyelitis eradication; wild poliovirus