1. Assessment of areas at increased risk for undetected poliovirus circulation in Ecuador Gustavo Dayan, MD Epidemiology Surveillance Division National Immunization Program Centers for Disease Control and Prevention

2. Background  1985 PAHO polio eradication goal in the Americas High vaccination coverage <5 years of age Adequate AFP surveillance system Outbreak control  1991 Last Polio Case in Peru  1994 Certification of poliomyelitis eradication  2000-01 Outbreak of vaccine-derived poliomyelitis in DOR and Haiti

3. Assessment of Countries at Risk for Poliovirus Circulation in the Americas  Protection of the population: National coverage with OPV3  Surveillance sensitivity: AFP rate per 100,000 population <15 years old with adequate stool specimen  Laboratory performance: Enterovirus isolation rate EPI bulletin PAHO 2001;6:1

4. OPV3 National Coverage Ecuador 1996-2000 80%

5. Ecuador rate AFP with adequate sample per 100,000 population < 15 years 1996-2000 0.8

6. Enterovirus isolation rate Ecuador 1996-2000 10%

7. Objectives  Rank provinces and areas at-risk to prioritize active search  Conduct active search of AFP cases in areas at increased risk  Evaluate unidentified AFP cases  Test environmental samples

8. Ecuador Ecuador  Area 280,000 km2  Population 12.41 million in 2001  Birth cohort 309,000  Political division Provinces Cantons Colombia Peru

9. Methods I Criteria to rank provinces  Vaccination coverage  OPV 3 > 80%  AFP surveillance quality  Reported > expected number of AFP cases per 100,000 population 1 stool specimen < 14days of AFP onset

10. Methodology II National level  List of all AFP cases reported during 1996-2001  Check viral isolation of cases  Inclusion of 2 national referral hospitals

11. Methodology III Provincial level  Provincial hospitals  Cantonal hospitals  Population density  Low OPV3 coverage rates  AFP rates per 100,000 population < 15 y: < 1  No reported AFP cases during the last 5 years

12. Methodology IV Health-care unit level  Review of hospital discharge data (3-5 y)  Identification of cases  Comparison with reported cases (PESS)  Review of individual records for unreported cases  Household visit for unreported cases

13. Methodology V Environmental Sampling  Area  Highest population density  Lowest OPV3 coverage  No. of samples  Size of area  Population accessibility to sewage  Analyzed at UNC Chapel Hill

14. Methodology VI Environmental Sampling Lab  L20 cell cultures  Microneutralization on cultures with CPE  Polivalent polioserum  Pool Sabin specific monoclonal antibodies  Intratypic differentiation  RT-PCR (CDC)  VP1 sequences of all poliovirus isolates

15. Classification of provinces at-risk for poliovirus circulation ECUADOR 1996-2000 I II III IV Category

16. Ecuador-Population in studied provinces Studied provinces 2 692 151 (21.2%) Esmeraldas 418 416 (3.3%) Manabí 1 267 844 (10%) Napo 89 717 (0.7%) Cotopaxi 303 499 (2.4%) Loja 429 010 (3.4%) Bolívar 183 665 (1.4%)

17. Hospitals selected for active search 1996- May 2001

18. AFP cases found through active search in health-care units 1996-May 2001 # Cases from the selected provinces No. of diagnoses reviewed= 326,725 *1998-2000

19. Annual distribution of AFP cases found through active search (not reported in PESS) n=6

20. Number of expected AFP cases vs. reported cases (PESS) and detected by active search in selected health care units 1996 – May 2001 Number of expected AFP cases vs. reported cases (PESS) and detected by active search in selected health care units 1996 – May 2001 *1998-2000

21. Viral isolates from AFP Cases Study provinces 1996-2000 YearProvinceVirusDiagnosis 2000LojaVAPolio 1VAP 1998ManabiEnterovirusEncephalitis 1997ManabiEnterovirusMeningitis 1997EsmeraldasEnterovirusMeningitis

22. Environmental sampling

23. Limitations  Sensitivity of the methodology  Cases may have presented to hospitals not chosen  Diagnosis may not have been reflective of AFP

24. Conclusions  No evidence for poliovirus circulation  Deficiencies in OPV 3 vaccination coverage  Deficiencies in AFP surveillance  Methodology easy to implement  SIAs and training on surveillance in areas at risk

25. Acknowledgements Rodrigo Rodríguez, Pan American Health Organizaton (PAHO) Jan Vinjé, University of North Carolina, Chapel Hill, NC Nancy Vásconez, Expanded Program of Immunizations (EPI), Ministry of Health, Ecuador Víctor Cáceres, Centers for Disease Control and Prevention (CDC), Atlanta Nicole Gregoricus, University of North Carolina, Chapel Hill, NC Mark Sobsey, University of North Carolina, Chapel Hill, NC Mauricio Landaverde, Pan American Health Organizaton (PAHO)

26. Classification of countries at-risk for undetected poliovirus circulation America region 1995-2000

27. Diagnoses of AFP cases Ecuador 1996-May 2001

28. Annual distribution of AFP cases found through active search (not reported in PESS)

29. Number of expected AFP cases vs. reported cases (PESS) and detected by active search in selected health care units 1996 – 2001* * May 2001