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Poliovirus Surveillance and Risks to Polio Eradication in India

Poliovirus Surveillance and Risks to Polio Eradication in India. Dr. Hamid Jafari WHO-NPSP. Risks to Polio Eradication in India. Reintroduction of virus into traditional endemic areas of UP and Bihar

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Poliovirus Surveillance and Risks to Polio Eradication in India

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  1. Poliovirus Surveillance and Risks to Polio Eradication in India Dr. Hamid Jafari WHO-NPSP

  2. Risks to Polio Eradication in India • Reintroduction of virus into traditional endemic areas of UP and Bihar • Persistent circulation in areas with recent transmission (West Bengal, Jharkhand) spreading back to endemic areas • Survival of poliovirus in the migrant and mobile communities leading to further spread • International importation • Persistent undetected transmission in traditional reservoir areas of UP and Bihar

  3. Risks to Polio Eradication in India - II • Introduction and survival of poliovirus in areas with low population immunity and/or other transmission risk factors outside UP and Bihar • Gaps in AFP surveillance or delays in detection of WPV • Delayed and/or inadequate response to importation

  4. Monthly incidence of WPV1 cases, 2005-2011 High transmission season Any residual WPV transmission is likely to be detected in the coming High Season for Polio

  5. Presentation - Key Questions • Is the overall sensitivity and timeliness of AFP surveillance adequate? • How robust is surveillance in the traditional endemic states of UP and Bihar? • What is the quality of surveillance in areas with recent transmission? • What is the quality of surveillance in areas where ‘orphan viruses’ have been isolated? • What is being done to enhance surveillance for poliovirus?

  6. AFP Surveillance Reporting Network 2011* N=33,114 Reporting site No. of Reporting Sites *Data as on 10 July 2011

  7. Non-polio AFP rate 2011* Year to date 2010 12.64 8.34 8.63 Year to date comparison 22973 AFP cases in 2011 vs. 22070 in 2010 Target: > 2 per 100,000 popn.<15 years *Data as on 10 July 2011

  8. % stool collection within 14 days 2010 2011* 84% 83% Target: > 80% *Data as on 10 July 2011

  9. Stool Specimens processed in polio laboratories - India Number of specimen processed >55,000 AFP cases investigated in 2010 65,011 83,528 91,148 100,102 109,098 2006 2007 2008 2009 2010 2011* *Data as on 10 July 2011

  10. Mean number of days from stool received in laboratory to final result of Wild and Vaccine viruses 2006 2007 2008 2009 2010 2011 *Data as on 10 July 2011

  11. Overall sensitivity and timeliness of AFP surveillance The overall sensitivity and timeliness of AFP and laboratory surveillance has continued to improve, however, some areas need further improvements

  12. Surveillance in endemic states Bihar & Uttar Pradesh

  13. Quality indicators, Bihar & UP, 2011 Non-HR blocks Non HR blocks Non-polio AFP rate HR blocks U.P. 16.59 U.P. HR 37.15 Bihar 28.78 Bihar HR 54.4 % adequate stool collection U.P. 82% U.P. HR 83% Bihar 88% Bihar 89 *Data as on 10 July 2011

  14. Surveillance in recent transmission areasWest Bengal, Jharkhand & Maharashtra

  15. WB & Jharkhand Non-polio AFP rate, 2011* Year to date No. of AFP cases West Bengal Jharkhand 7.26 Jharkhand West Bengal 4.35 2011* 2010* *Data as on 10 July 2011

  16. WB & Jharkhand 2010 2011* % adequate stool collection Jharkhand 82% Jharkhand 82% West Bengal 87% West Bengal 86% *Data as on 10 July 2011

  17. Maharashtra Non-polio AFP rate, 2011* Year to date No. of AFP cases 4.41 2011* 2010* *Data as on 10 July 2011

  18. Maharashtra 2010 2011* % adequate stool collection 84% 83% *Data as on 10 July 2011

  19. Surveillance in the traditional endemic states of UP and Bihar: Surveillance in endemic states is of excellent quality with very high case reporting rates in high risk blocks • Quality of surveillance in areas with recent transmission AFP case reporting has increased in 2011 compared with 2010, however, a few key districts need further improvements, especially in adequate sample collection

  20. Surveillance in areas with ‘orphan’ wild polioviruses

  21. Example: Orphan WPV1 detected in UP >1.5% genetic distance Transmission detected after a gap of 13 months

  22. Districts with ‘Orphan’ viruses, 2008-2010 WPV1 cases with >1% Genetic distance 4 districts where same genetic strain detected more than once (interval range: 8-10 months) 28 Orphan WPV1 isolated in 23 districts 1 isolate each in Mumbai & Delhi sewage

  23. Quality of surveillance in districts with orphan viruses>1% genetic distance, Jan 2010 – June 2011 Non-polio AFP rate % adequate stool collection *Data as on 10 July 2011

  24. Districts with ‘Orphan’ viruses, 2008-2010 WPV1 cases with >1% Genetic distance WPV1 cases with >1.5% Genetic distance 10 WPV1 from 8 districts 1 isolate each in Mumbai & Delhi sewage

  25. Quality of surveillance in districts with orphan viruses>1.5% genetic distance Non-polio AFP rate *Data as on 10 July 2011

  26. 2008 Bihar WPV1 in Saharsa Virus detection intervals: 10 months Virus detection intervals: 10 months and 9 months

  27. The single 2008 Saharsa isolate ancestor of all subsequent WPV1 strains

  28. Enhanced Surveillance in Kosi River Area No. of AFP cases 2008 WPV1 case in Kosi River area 2010 2007 2008 2009 2011* * data as on 10 July 2011

  29. Surveillance in Districts with ‘Orphan’ WPV Isolates • Most Districts with orphan strains have strong surveillance and are unlikely hosts of prolonged undetected transmission • Kosi River area of Bihar was the most likely region with undetected transmission until 2009, however, surveillance has been enhanced substantially in this area • Many orphan strains likely related to transmission among migrants or in immune populations • Isolation of orphan strains in Murshidabad and Nasik districts in 2010 highlight the need for further surveillance improvements in these districts

  30. Special Strategies to Enhance Surveillance

  31. Role of Migrants in Survival and Spread of Poliovirus Example of most recent WPV1 case

  32. Migration status of WPV1 cases 2007-11 Uttar Pradesh Non epidemic UP* (N= 118) (N= 56) Bihar Rest of India (N= 48) (N= 90) *Non epidemic UP excludes Moradabad, JP Nagar, Badaun, Kanshiram Nagar, Bareilly and Rampur districts *Data as on 10 July 2011

  33. Pattern of importations of WPV : 2005-11 High risk: > 8 importations and > 5 years with importations Medium risk: : > 5 importations and 3 - 4 years with importations

  34. Risk of WPV importation - outside UP & Bihar, 2005-11 Importations in >=4 years Importations in 2-3 years Importation in a year with multiple cases No importation or importation in a year with single case *: data as on 12 March 2011

  35. Enhanced Surveillance Among MigrantsYear to date comparisons of reported AFP cases India 6 States at high risk of importations UP & Bihar *Data as on 10 July 2011

  36. Non-polio AFP cases in migrants 2010 2011* N=691 N=1588 Estimated non-polio AFP rate** amongst migrants ** Estimate based on the number of migrant children vaccinated in SIAs *Data as on 10 July 2011

  37. Expansion of Environmental Surveillance in High Importation Risk Areas Further expansion of sites in Delhi & Maharashtra Sewage sampling sites 2010 Sewage sampling initiated 2011 State planned for 2011 States planned for 2012

  38. Surveillance quality assurance Ongoing surveillance reviews 2010 2011

  39. Example: Delhi surveillance review 2010,Key concerns 2010 2009 2011* • Inadequate informer network in areas with migrants • Need for further sensitization of reporting network Outcome: Increased number of AFP cases reported No. of AFP surveillance workshops, 2011 Number of reporting sites Number of sensitization visits No. of AFP Cases Reported 2010 2011 *Data as on 10 July 2011

  40. Special Surveillance Strategies • Special efforts ongoing to measure and increase surveillance among migrants • Expansion of environmental surveillance guided by risk of importation • Ongoing independent surveillance reviews targeted to high risk areas and populations • Assessment of local surveillance quality will be a key component of the ongoing risk analyses by states as they develop their polio emergency and response plans

  41. Summary • Overall, a sensitive surveillance system that meets or exceeds international standards • A reliable and efficient laboratory network despite an increasingly heavy workload • High AFP reporting rates in endemic states, particularly in high risk blocks • Improvements in case reporting in areas with transmission in 2010, however, a few districts need further strengthening • Any residual transmission is likely to be detected in the ensuing high season for polio

  42. Summary • Orphan strains have been detected after an interval of up to 13 months very recently. • Migrants have contributed significantly to undetected transmission • Focused efforts ongoing to promptly detect transmission in migrant populations • Expansion of environmental surveillance will help early detection of virus in high risk areas • Most districts with orphan isolates have strong surveillance. Surveillance in Kosi River area has improved substantially.

  43. Thank You

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