title: Outbreaks of paralytic poliomyelitis during 1996-2012: the changing epidemiology of a disease in the final stages of eradication.
abstract: BACKGROUND
  Despite substantial progress toward eradication of poliomyelitis, the risk of poliomyelitis outbreaks resulting from virus importations into polio-free areas persists. We reviewed the changing epidemiology of outbreaks in the final stages of the eradication initiative.
  
  
  METHODS
  Available literature on outbreaks of poliomyelitis caused by wild polioviruses between 1996 and 2012 was reviewed.
  
  
  RESULTS
  During this period, there were 22 outbreaks involving 39 countries. Outbreaks ranged in size from 1 to 1335 cases. These outbreaks caused 4571 cases, representing 21% of all cases reported during this period. Five outbreaks involved multiple countries. In 76% of outbreaks (16/21) with a known age distribution, cases concentrated among children aged <5 years; in 19% (4/21), most cases were among adolescents and adults. The outbreaks among adolescents and adults were associated with higher case-fatality ratios, ranging from 12% in Albania in 1994 to 41% in the Republic of Congo in 2010. The majority of outbreaks were controlled within 6 months with oral poliovirus vaccine.
  
  
  CONCLUSIONS
  Importations resulting in epidemic transmission of wild poliovirus caused thousands of cases of paralysis often in countries where poliomyelitis had not occurred for many years. The changing epidemiology, with cases and higher case-fatality ratios among adults, increased the severity of these outbreaks.
authors.affiliation: World Health Organization, Geneva, Switzerland.
authors.forename: Ondrej
authors.initials: O
authors.lastname: Mach
authors.affiliation: World Health Organization, Geneva, Switzerland.
authors.forename: Rudolf H
authors.initials: RH
authors.lastname: Tangermann
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Steve G
authors.initials: SG
authors.lastname: Wassilak
authors.affiliation: World Health Organization, Geneva, Switzerland.
authors.forename: Simarjit
authors.initials: S
authors.lastname: Singh
authors.affiliation: World Health Organization, Geneva, Switzerland.
authors.forename: Roland W
authors.initials: RW
authors.lastname: Sutter
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002675:Child, Preschool; D060740:Disease Eradication; D004196:Disease Outbreaks; D005260:Female; D014943:Global Health; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011051:Poliomyelitis / Q000453:epidemiology* / Q000517:prevention & control* / Q000635:transmission; D055815:Young Adult
keywords: outbreak; poliomyelitis; poliovirus eradication