jueves, 10 de noviembre de 2011
Progress Toward Poliomyelitis Eradication --- Afghanistan and Pakistan, January 2010--September 2011
Progress Toward Poliomyelitis Eradication --- Afghanistan and Pakistan, January 2010--September 2011Weekly
November 11, 2011 / 60(44);1523-1527
Indigenous transmission of wild poliovirus (WPV) has never been interrupted in Afghanistan, Pakistan, India, and Nigeria (1--3). Among those countries, Afghanistan and Pakistan represent a common epidemiologic reservoir (1). This report updates previous reports (1,4) and describes polio eradication activities and progress in Afghanistan and Pakistan during January 2010--September 2011, as of October 31, 2011, and planned activities during 2011--2012 to address challenges to polio eradication. In Afghanistan, WPV transmission during 2010--2011 predominantly occurred in the conflict-affected South Region and the adjacent Farah Province of the West Region. During 2010, 25 WPV cases were confirmed in Afghanistan, compared with 38 in 2009; 42 WPV cases were confirmed during January--September 2011, compared with 19 for the same period in 2010. In Pakistan, WPV transmission during 2010--2011occurred both in conflict-affected, inaccessible areas along the common border with Afghanistan and in accessible areas; 144 WPV cases were confirmed in 2010, compared with 89 in 2009, and 120 WPV cases were confirmed during January--September 2011, compared with 93 during the same period in 2010. In Pakistan, the president launched a National Emergency Action Plan for polio eradication in January 2011, emphasizing the key role and responsibility of political and health-care leaders at the district and subdistrict (union council) levels. Enhanced commitment, management, and oversight by provincial and district authorities will be needed to achieve further progress toward interruption of WPV transmission in Pakistan. Continued efforts also will be needed to enhance the safety of vaccination teams within insecure areas of both countries.
Estimated national routine immunization coverage of infants with 3 doses of oral polio vaccine (OPV3) in 2010 was 66% in Afghanistan and 88% in Pakistan (5). However, 2010 surveillance data for acute flaccid paralysis (AFP)* indicated lower national coverage in Pakistan and wide subnational variation in both countries. Based on parental recall and immunization cards, routine OPV3 coverage among children aged 6--23 months with nonpolio AFP (NPAFP) was 64% nationally in Afghanistan (26% combined in the conflict-affected South Region and Farah Province; 71% in the West Region, excluding Farah Province; and 80% in the rest of the country), and 63% nationally in Pakistan (58% combined in the conflict-affected Khyber Pakhtunkhwa [KP] Province and the Federally Administered Tribal Areas [FATA] and 72%, 59%, and 29% in the more secure provinces of Punjab, Sindh, and Balochistan, respectively).
During January 2010--September 2011, house-to-house supplementary immunization activities (SIAs)† targeting children were conducted using different OPV formulations, including trivalent (tOPV), monovalent type 1 (mOPV1) and type 3 (mOPV3), or bivalent with types 1 and 3 (bOPV). During this period, Afghanistan conducted seven national immunization days (NIDs); seven subnational immunization days (SNIDs) in the East, Southeast, and South regions, and in Farah Province of the West Region (which targeted about 50% of the national population of children); and several smaller-scale, mop-up or short-interval additional dose (SIAD)§ SIAs after a preceding larger SIA, targeting children around confirmed cases or in high-risk districts. Pakistan conducted nine NIDs; seven SNIDs in the main WPV transmission areas of KP, FATA, southern Punjab, Balochistan, and Sindh, during which high-risk districts were targeted; and several smaller SIAs, targeting children around confirmed cases or migratory and other high-risk populations.
During 2010--2011, as in past years, SIAs were unable to reach children living in areas inaccessible¶ because of security problems. In Afghanistan, the estimated percentage of targeted children who were living in inaccessible areas in the South Region was 6%--10% during SIAs conducted in 2010 and 5%--21% during SIAs in January--September 2011, affecting 72,000--274,000 children during each campaign. In Pakistan, the percentage of targeted children who were living in SIA-inaccessible areas of KP during SIAs decreased from 1%--2% in January-March 2010 to <1% during April 2010--July 2011, a decline from 30,000--100,000 children to <6,000 children missed per campaign. In FATA, however, the estimated percentage of targeted children living in SIA-inaccessible areas was 20%--31% during 2010 and 20%--24% during January--July 2011, affecting approximately 225,000--350,000 children during each SIA. In addition, although large parts of the South Region in Afghanistan, and KP and FATA in Pakistan, remained accessible to local vaccination teams during SIAs, security problems often prevented external monitors and supervisors from entering and assessing the quality and coverage of SIAs.
AFP surveillance performance is monitored by standard performance indicators.** In 2010, the annual national nonpolio AFP rate (per 100,000 population aged <15 years) was 9.2 in Afghanistan (range among the eight regions: 6.2--12.8), and 6.9 in Pakistan (range among the six provinces/territories: 2.8--10.3). The percentage of AFP cases for which adequate specimens were collected was 93% in Afghanistan (range: 83%--97%) and 89% in Pakistan (range: 81%--91%) (Table).
The polio laboratory at the National Institute of Health (NIH) in Islamabad provides laboratory support for AFP surveillance in both countries, including genomic sequencing of poliovirus isolates. During January 2010--September 2011, the NIH laboratory processed 2,894 stool specimens from Afghanistan and 9,352 from Pakistan. During 2010--2011, to supplement AFP surveillance in Pakistan, weekly sewage sample collection to test for polioviruses was conducted at 18 sites in six cities: Karachi in Sindh; Lahore, Rawalpindi, and Multan in Punjab; Peshawar in KP; and Quetta in Balochistan.
In Afghanistan, 25 WPV cases (17 WPV type 1 [WPV1], eight WPV type 3 [WPV3]) were reported during 2010, compared with 38 WPV cases (15 WPV1, 23 WPV3) in 2009; 42 WPV cases (all WPV1) were reported during January--September 2011, compared with 19 for the same period in 2010, including 30 cases (71%) reported during August--September 2011 (Table, Figures 1 and 2). During January 2010--September 2011, 48 (72%) of 67 WPV cases were among children aged <36 months. Among the 67 children, 17 (25%) received no OPV doses, 20 (30%) received 1--3 OPV doses, and 30 (45%) received ≥4 OPV doses. During 2010, WPV cases were reported in 15 (5%) of 325 districts, including 11 high-risk districts†† of the South Region and Farah Province, the West Region, and four other districts (three in the East Region and one in the Northeast Region). During January--September 2011, WPV cases were reported from 19 (6%) districts, including 16 high-risk districts of the South Region and Farah Province.
In Pakistan, 144 WPV cases (120 WPV1, 24 WPV3) were reported in 2010, compared with 89 WPV cases (60 WPV1, 28 WPV3, one WPV1/WPV3 coinfection) during 2009; 120 WPV cases (118 WPV1, two WPV3) were reported during January--September 2011, compared with 93 cases for the same period in 2010 (Table, Figures 1 and 2). During January 2010--September 2011, 227 (86%) of 264 WPV cases were among children aged <36 months. Among the 264 children, 75 (28%) received no OPV doses, 63 (24%) received 1--3 OPV doses, and 126 (48%) received ≥4 OPV doses. WPV cases were reported in 40 (30%) of 135 districts in Pakistan during 2010, compared with 34 (25%) districts during 2009, and from 36 (27%) districts during January--September 2011, including 18 districts not affected during 2010. During 2010, 98 (68%) of 144 cases were from KP and FATA and 39 (27%) from Balochistan and Sindh; during January--September 2011, 44 (37%) of 120 cases were from KP and FATA and 73 (61%) from Balochistan and Sindh (Table, Figure 2).
WPVs have been isolated frequently from sewage samples collected in all major cities in Pakistan since mid-July 2010. WPVs have been isolated not only from sewage samples in cities such as Quetta in Balochistan, where confirmed polio cases have been reported, but also from Lahore, Multan, and Rawalpindi in Punjab, where only two confirmed WPV cases have been reported from rural districts since November 2010.
In both countries, WPV3 transmission has declined, from 32 cases in 2010 to two cases in 2011. The most recent WPV3 case in Afghanistan occurred in the South Region in April 2010. The most recent WPV3 cases in Pakistan were reported from FATA in June and September 2011, and the most recently detected WPV3 in sewage was in October 2010 from a sample collected in Karachi.
WPV genomic sequencing data for 2010--2011 indicate that transmission of several genetic clusters of WPV1 continued in and among the South and West regions of Afghanistan and in KP, FATA, Sindh, and Balochistan in Pakistan during 2010--2011. Sequence data indicate missed detection of WPV cases in Pakistan and suggest that performance indicators are not revealing surveillance weaknesses in some subnational areas. The genetic diversity of WPV3 decreased during this period, coincident with the decreased number of cases; >95% of the WPV3 in 2010--2011 were from one genetic cluster.
World Health Organization (WHO) Eastern Mediterranean Regional Office, Cairo, Egypt; WHO Afghanistan, Kabul; WHO Pakistan, Islamabad; Polio Eradication Dept, WHO, Geneva, Switzerland. Global Immunization Div, Center for Global Health; Div of Viral Diseases, National Center for Immunization and Respiratory Diseases, CDC. Corresponding contributor: Jim Alexander, firstname.lastname@example.org, 404-639-8906.
In Afghanistan, WPV transmission was lower in 2010, compared with 2009 (25 cases versus 38 cases, respectively), but it increased during January--September 2011 (42 cases), compared with January--September 2010 (19 cases); nearly 75% (30) of the 2011 cases were reported during August and September. During January 2010--September 2011, as in previous years, the majority of WPV cases were reported from insecure districts in the South Region and the adjacent Farah Province in the lower West Region, where children living in inaccessible areas were not reached during SIAs. Since 2008, multiple strategies have been implemented to immunize unreached children, including systematic engagement of local leaders, increased engagement of nongovernmental organizations delivering basic health services, negotiations with parties in conflict, and use of SIAD SIAs to administer a dose of OPV within 1--2 weeks of a prior dose during negotiated periods of security; these strategies have had varying success.§§ During 2010--2011, approximately 100,000 children in the South Region were unimmunized in each of the SIAs.
WPV transmission in Pakistan increased during 2010, compared with 2009 (144 versus 89 cases, respectively), and during January--September 2011, compared with a similar period in 2010 (120 cases versus 93 cases, respectively), affecting high-risk districts in KP and FATA, as well as districts in Balochistan and Sindh. Sewage sampling provided evidence of WPV transmission in areas with few WPV cases, such as Punjab. In the northwest, WPV transmission continued because of limited access to children during SIAs in insecure areas of KP and FATA. In Balochistan and Sindh, WPV circulation continued because of weak routine immunization programs and managerial and operational gaps during SIAs, compounded by large-scale population movements from insecure areas along the common border and from flood-affected districts in Sindh and other areas.
In Pakistan, devolution of health authority from federal to provincial governments occurred during 2011, and might adversely affect polio eradication activities. The National Emergency Action Plan for polio eradication, launched in early 2011, has the essential elements for making progress, but has not been implemented effectively in key districts and union councils. A key gap to fill will be the designation of a medical officer in each high-risk union council to oversee the preparation and implementation of polio campaign activities within the jurisdiction. Political involvement has been enhanced at the federal and provincial levels, but effective monitoring of the activities of provincial, district, and union council authorities is urgently needed, and specific mechanisms need to be established to hold officials accountable for program performance. In September 2011, the Global Polio Eradication Initiative (GPEI) Independent Monitoring Board assessed the situation in Pakistan, noted that the country has made little tangible advance over the last 18 months, and recommended that a fundamental review of strategy and implementation be undertaken.
The GPEI Strategic Plan for 2010--2012 has aimed for complete interruption of WPV transmission in two of the four remaining endemic countries by the end of 2011 and in all countries by the end of 2012 (1,6). In Afghanistan and Pakistan, with predominant use of tOPV and bOPV in SIAs, a marked decline of WPV3 cases occurred during 2010--2011. However, ongoing uncontrolled WPV1 transmission in Pakistan and, to a lesser extent, transmission in parts of Afghanistan, remain as substantial challenges to the 2012 GPEI target and as threats to the achieving the GPEI goal.
1.CDC. Progress toward interruption of wild poliovirus transmission---worldwide, January 2010--March 2011. MMWR 2011;60:582--6.
2.CDC. Progress toward poliomyelitis eradication---Nigeria, January 2010--June 2011. MMWR 2011;60:1053--7.
3.CDC. Progress toward poliomyelitis eradication---India, January 2010--September 2011. MMWR 2011;60:1482--6.
4.CDC. Progress toward poliomyelitis eradication---Afghanistan and Pakistan, 2009. MMWR 2010;59:268--72.
5.World Health Organization. WHO vaccine-preventable diseases monitoring system: 2010 global summary. Geneva, Switzerland: World Health Organization; 2010. Available at http://www.who.int/vaccines/globalsummary/immunization/countryprofileselect.cfm. Accessed August 30, 2011.
6.World Health Organization. Global Polio Eradication Initiative Strategic Plan 2010--2012. Geneva, Switzerland: World Health Organization; 2010. Available at http://www.polioeradication.org/resourcelibrary/strategyandwork/strategicplan.aspx. Accessed August 30, 2011.
* Vaccination histories of children aged 6--23 months with AFP who do not test as WPV positive are used to estimate OPV coverage of the overall target population and to verify national reported routine vaccination coverage estimates.
† Mass campaigns conducted for a brief period (days to weeks) in which 1 dose of oral poliovirus vaccine is administered to all children aged <5 years, regardless of vaccination history. Campaigns can be conducted nationally or in sections of the country.
§ SIADs are used during negotiated periods of security to vaccinate children in otherwise inaccessible areas in which a mOPV or bOPV dose is administered within 1--2 weeks of the previous dose.
¶ Areas considered too dangerous by the World Health Organization (WHO) and the local government to conduct an SIA.
** The quality of AFP surveillance is monitored by performance indicators that include 1) the detection rate of NPAFP cases and 2) the proportion of AFP cases with adequate stool specimens. World Health Organization (WHO) operational targets for countries with endemic polio transmission are a NPAFP detection rate of at least two cases per 100,000 population aged <15 years and adequate stool-specimen collection from >80% of AFP cases, in which two specimens are collected at least 24 hours apart, both within 14 days of paralysis onset, and shipped on ice or frozen packs to a WHO-accredited laboratory, arriving in good condition.
†† High-risk districts include those persistently affected by WPV transmission and those near persistently affected districts.
§§ The success of these strategies has been measured programmatically (e.g., whether a district is "open" during an SIA and the target population of children aged <5 years is accessible, whether the numbers and percentages of unreached children were reduced, whether the vaccination coverage of children with nonpolio AFP improved, or whether WPV circulation decreased).
Progress Toward Poliomyelitis Eradication --- Afghanistan and Pakistan, January 2010--September 2011