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Progress Toward Poliomyelitis Eradication --- Afghanistan and Pakistan, January 2003--May 2004
Since the 1988 World Health Assembly resolution to eradicate poliomyelitis, the number of countries where polio is endemic decreased from approximately 125 to six by the end of 2003 (1,2). In 2003, poliovirus importations were reported in 10 countries, including eight in West and Central Africa, one in Southern Africa (Botswana), and one in the Middle East (Lebanon) (2). Two countries where poliovirus remains endemic are Afghanistan and Pakistan, which are analyzed together because of their geographic proximity, frequent cross-border population movements, and genetically similar wild poliovirus (WPV) lineages. This report describes intensified polio eradication activities in Afghanistan and Pakistan during January 2003--May 2004, summarizes progress made toward eradication, and highlights the remaining challenges to interrupting poliovirus transmission.
Routine and Supplementary Immunization Activities
Routine immunization programs in both Afghanistan and Pakistan remain inadequate. In 2002, reported overall coverage among infants with 3 doses of OPV (OPV3) was 48% in Afghanistan and 63% in Pakistan; moreover, wide variation existed at the subnational level (3).
The number and intensity of supplemental immunization activities (SIAs) in both Afghanistan and Pakistan were increased during 2003--2004, compared with previous years. In 2003, Pakistan conducted four rounds of national immunization days* (NIDs). Four rounds of subnational immunization days* (SNIDs), of which three covered >50% of the target population aged <5 years, also were conducted. In Afghanistan, four NID and three SNID rounds in 2003 were synchronized closely with rounds in Pakistan. During 2004, Pakistan has conducted three rounds of NIDs and one SNID round targeted at known virus reservoirs and districts with previously inadequate SIAs and low routine coverage. Afghanistan conducted two parallel NID rounds in the spring, followed by two rounds of "mopping-up" vaccination in June and July, targeting the known virus reservoir in the southern and southeastern areas of the country.
The quality of SIAs is monitored in both countries by measuring process indicators during vaccination rounds and conducting immediate postcampaign coverage assessments. Monitoring identifies areas with inadequate SIAs and enables improvement of subsequent SIA rounds. The quality of SIAs in Pakistan has improved since January 2003 through the intensified efforts of government officials supplemented by development partners§ and additional United Nations agency support staff at the district level. The additional staff include approximately 100 district support officers assigned for 3--6 months and approximately 300 campaign support staff assigned for a 3-week period for the SIAs. In Afghanistan's southern and southeastern regions, 40 additional local staff were hired in early 2004 to support SIA planning, implementation, and monitoring at the district level, and to overcome access problems caused by deteriorating security. Process indicators and postcampaign coverage assessments demonstrate that SIA quality was maintained or improved in both countries during the previous 18 months.
In Pakistan, the proportion of acute flaccid paralysis (AFP) patients aged <24 months with >3 OPV doses (i.e., both routine and SIA doses) increased from 76% in 2003 to 83% during the first 5 months of 2004. This proportion remained at 81% for most of Afghanistan, except in the southern and southeastern regions, where it decreased from 80% (2003) to 76% (January--May 2004)¶.
The quality of AFP surveillance is evaluated by two key indicators: the rate of reported AFP cases not caused by WPV (target: nonpolio AFP rate of >1 case per 100,000 children aged <15 years) and the proportion of persons with AFP with adequate stool specimens (target: >80%). The national nonpolio AFP rate for Pakistan in 2003 was 3.0 per 100,000 children aged <15 years, ranging from 2.5 in Punjab province to 4.2 in Balochistan province; as of May, the annualized rate in 2004 was 2.9. The percentage of persons with adequate stool specimens was 89% and 90% in 2003 and 2004 (provincial ranges: 85%--91% and 79%--92%), respectively.
Nonpolio AFP rates in Afghanistan were 4.0 per 100,000 children aged <15 years in 2003 and 4.2 in 2004, with the percentage of persons with adequate stool specimens at 88% in 2003 and 93% in 2004. Nonpolio AFP rates in 2003 ranged from 2.1 in the southeastern region to 5.5 in the western region.
The World Health Organization-accredited Regional Reference Laboratory at the National Institute of Health in Islamabad, Pakistan, performs virologic testing of stool specimens from both Afghanistan and Pakistan. The proportion of specimens with nonpolio enterovirus (NPEV) isolated, an indicator of the quality of stool-specimen transport and sensitivity of laboratory testing, was 22% and 25% in 2003 for Afghanistan and Pakistan, respectively; NPEV isolation rates during January--May 2004 were 19% for each country (Table).
Incidence of Polio
The number of confirmed cases of polio in Pakistan increased from 90 cases in 33 districts in 2002 to 103 cases in 48 districts in 2003. However, beginning in the second half of 2003, during peak transmission months, the number of cases began to decline; 55 cases were reported in the second half of 2003, compared with 62 during the same period in 2002. During the first 5 months of 2004, a total of 16 confirmed polio cases, 11 caused by WPV type 1 and five caused by WPV type 3, were reported, compared with 34 cases during the same period in 2003.
At the provincial level, progress has been variable. During the first half of 2003, transmission continued in four virus reservoirs: northern Sindh, where the most intense transmission occurred; southern Punjab; and two areas in Northwest Frontier Province (NWFP) (Figure). In the second half of 2003, during peak transmission months, one case was reported from the northern Sindh reservoir; however, transmission occurred in the Quetta area of Balochistan and intensified in NWFP. Subsequently, polio was reintroduced into the central Punjab area, which had been free of indigenous transmission of virus for >2 years; the virus originated in southern NWFP. In 2004, WPV circulation has been limited to four reservoirs that also had transmission in 2003. Transmission in central Punjab was limited and has not been detected since February. In addition, other transmission areas have not had cases in 2004, including the Quetta area of Balochistan province, Hyderabad district of Sindh province, and Lahore in central Punjab province. Karachi district has had one case in 2004.
Afghanistan reported eight polio cases in 2003, five caused by WPV type 1 and three by WPV type 3. Two WPV type 1 cases and one WPV type 3 case have been reported in 2004 (Table). The two WPV type 1 cases occurred in January and February in Helmand and Kandahar provinces, respectively, in southern Afghanistan; the WPV type 3 case occurred in May in Nangahar province in east Afghanistan. Sequence relationships among isolates suggest that the WPV type 1 virus strains transmitted in 2003 (including in Herat province in western Afghanistan) and in 2004 are part of the endemic WPV reservoir shared by southern and southeastern Afghanistan and Pakistan. The WPV type 3 viruses found in the south, southeast, and east since 2003 probably represent introductions from Pakistan.
Reported by: Ministry of Public Health; Country Office of the World Health Organization; United Nations Children's Fund (UNICEF), Kabul, Afghanistan. Regional Office for the Eastern Mediterranean Region, World Health Organization, Cairo, Egypt. National Institute of Health; Country Office of the World Health Organization; United Nations Children's Fund, Islamabad, Pakistan. Vaccines and Biologicals Dept, World Health Organization, Geneva, Switzerland. Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; Global Immunization Div, National Immunization Program, CDC.
Pakistan experienced an overall increase in the number of polio cases in 2003 compared with 2002; however, the increased number, intensity, and quality of SIAs in 2003 and 2004 have resulted in a decrease in polio incidence that began in mid-2003. In Pakistan, the majority of WPV circulation in 2004 has been limited to four areas, with intensity of transmission during the first 5 months of 2004 substantially lower than that in 2003. Notably, no cases have been reported in all of Balochistan province since October 2003. Central Punjab, where renewed transmission occurred during 2003, has not reported WPV since February 2004.
Challenges remain for the program in Pakistan. The most active areas of transmission are now in the tribal areas of the country, especially in NWFP. Cultural practices in areas of NWFP and in certain traditional communities in other provinces limit the involvement of women in SIAs, thereby reducing access to young children. The NWFP provincial government has been increasingly active in working with community and religious leaders toward better awareness and acceptance of polio vaccination and recruitment of community mobilizers.
In Afghanistan, progress toward improving the quality of SIAs is suggested by process indicators and coverage data. Data from 2004 suggest that SIA quality was maintained or improved in all areas except the southeastern and southern region, where performance decreased in 2004 compared with 2003. The main constraint for polio eradication activities in Afghanistan is increasingly restricted access to extensive areas bordering Pakistan, potentially compromising the quality of both SIA activities and AFP surveillance.
Although thousands of Afghan refugee families have returned home from Pakistan, intense cross-border migration continues in both directions, favoring continuous virus movement between both countries. The two countries must continue to work together closely to interrupt poliovirus transmission, which can only occur if both countries maintain sensitive surveillance systems and further improve the quality of their SIAs, especially in areas where cultural practices limit access and in areas that are not secure.
* National or subnational mass campaigns during a limited number of days in which 2 doses of OPV are administered to all children (usually aged <5 years), regardless of previous vaccination history, with an interval of 4--6 weeks between doses.
More intensified campaigns that are conducted in areas of poliovirus transmission.
§ Polio eradication efforts in Afghanistan and Pakistan are supported by the governments of those countries, Japan, United Kingdom, Netherlands, Bill and Melinda Gates Foundation, United Nations Children's Fund (UNICEF), International Committee of the Red Cross, the International Committee of the Red Cross and Red Crescent Societies, Rotary International, U.S. Agency for International Development, World Health Organization, and CDC.
¶ National polio eradication programs analyze the OPV vaccination status (routine and supplemental doses) of children aged <5 years or <24 months with nonpolio AFP as a proxy for OPV coverage in these age groups.
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