The Eradication of Poliomyelitis in Egypt: Critical Factors Affecting Progress to Date

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1 S56 The Eradication of Poliomyelitis in Egypt: Critical Factors Affecting Progress to Date R. Bruce Aylward, Esmat Mansour, EI Said Aly Don, Ahmed Haridi, Abdulla Abu EI Kheir, and AtefHassan World Health Organization, Geneva, Switzerland; Child Survival Project and Department of Communicable Disease Control, Ministry of Health, Cairo, Egypt Poliomyelitis eradication activities in Egypt were reviewed to identify the critical factors for the progress seen by 1995 and to highlight problems that could be avoided in other countries in which poliomyelitis is endemic. National immunization and surveillance data demonstrate that the combination of high routine immunization coverage' (>85%) with oral polio vaccine combined with two properly conducted rounds of national immunization days (NIDs) resulted in a 75% reduction in reported polio cases between 1992 and Available data suggest that earlier control strategies, such as single-round NIDs in 1990 and 1991, the administration of inactivated poliovirus vaccine (IPV) at 2 months of age in , and the use of "mop-up" campaigns while wild poliovirus was still widespread, did not contribute substantially to the recent decline in cases. Proper implementation of the World Health Organization's recommended strategies can eliminate wild poliovirus circulationin the large, densely populatedtropicalcountriesin which poliomyelitis remainsendemic. In 1988, the World Health Assembly voted to eradicate wild polioviruses by the year 2000 [1]. The technical feasibility of the goal was confirmed in September 1994, when an international commission certified that wild poliovirus has been eliminated from the Western Hemisphere [2]. Despite such progress, the disease remains endemic in a number of large, densely populated countries in Asia and Africa [3, 4]. Continued circulation of wild polioviruses in such countries poses a threat to both local populations and regions that have already eliminated the virus [2, 5]. Egypt is one poliovirus-endemic country where the early interruption of wild poliovirus circulation has been an international priority [6]. Ongoing efforts to establish a large block of polio-free countries stretching from the Magreb countries of North Africa to the Arab States of the Gulf depend on progress in Egypt [7]. Additionally, molecular characterization of wild polioviruses has indirectly linked Egyptian strains with distant cases in other parts ofthe world. Despite a long history of polio control activities and a strong childhood immunization program, poliomyelitis remained widely endemic in Egypt until quite recently [8], leading to questions as to the feasibility of polio eradication. Here we review the epidemiology of polio in Egypt through 1995, demonstrating that once the recommended strategies of Financial support: This study was supported by the US Agency for International Development through the technical assistance contract of Clark Atlanta University (AID # ) with the Egyptian Ministry ofhealth Child Survival Project, Cairo, Egypt. The views presented are those of the authors. Reprints or correspondence: Dr. R. Bruce Aylward, Expanded Programme on Immunization, Global Programme for Vaccines and Immunization, World Health Organization, 20 Ave. Appia, 1211-Geneva-27, Switzerland. The Journal oflnfectious Diseases 1997;175(Suppll):S by The University of Chicago. All rights reserved /97/ $01.00 the World Health Organization (WHO) are properly implemented, widespread poliovirus circulation can be interrupted within 2 or 3 years. The experience in Egypt is used to illustrate problems that might be avoided in the remaining polio-endemic countries as they undertake eradication programs. Background Based on the extrapolation of 1986 census data, the 1994 population of Egypt was 59,000,000, with million births annually. Administratively, there are 27 governorates, which are further divided into 223 districts (218 and 214 in 1992 and 1993, respectively). Twenty-five percent ofthe population is concentrated in the 3 governorates that constitute greater Cairo (Cairo, Giza, Qalyoubia). The percentage of the total population living in the Nile Delta (8 governorates), Upper Egypt (8 governorates), and other governorates (8) is 43%, 28%, and 4%, respectively. About 15% of the population is < 5 years old and 42% is < 15 years old. In summary, the WHO-recommended strategies for polio eradication from countries in which poliomyelitis is endemic consist of high routine infant immunization with at least three doses of oral polio vaccine (OPV3), national immunization days (NIDs) and "mopping up," and surveillance for acute flaccid paralysis (AFP) [9-11]. During NIDs, all children <5 years old should receive two OPV doses 1 month apart, regardless of their prior immunization status, in the low season for polio transmission [9]. Mopping up, consisting of two rounds of house-to-house immunization, should be conducted in geographically restricted high-risk areas [12] after NIDs have reduced wild poliovirus transmission to focal areas. To rule out ongoing wild poliovirus circulation, all AFP cases among children < 15 years old should be investigated [13], with the analysis of 2 properly collected stool specimens in an accredited laboratory [14].

2 JID 1997; 175 (Supp1 1) Polio Eradication in Egypt S57 Monthly reported cases of polio 500r-r , Figure 1. Immunizationcampaigns with oral polio vaccine (OPY) and reported cases of poliomyelitis by month, Egypt, * No. of arrows correspondsto no. ofimmunization rounds conducted. Routine = routine OPV doses delivered by national or subnational campaigns. NIDs = supplementary OPV doses delivered during national immunization days. Mop-up = supplementary OPV doses given house-to-house in high-risk areas Campaigns* 1 Routine.+. NICs 'Mop-up' II Polio cases o Immunization in Egypt before the Eradication Initiative Polio has been a recognized health problem in Egypt since the time of the Pharaohs; an Egyptian tombstone from the year 1500 B.C. contains the first known illustration or record of a case. Before obligatory childhood immunization was instituted nationwide in 1968, the annual incidence of paralytic polio was estimated to be cases/100,000 total population on the basis of records from the National Polio Institute. Although 65% of the infants were being immunized against polio by 1975 and the incidence of the disease had fallen to 6.5 cases/ 100,000 population, >2000 cases continued to be reported annually. While routine immunization services were being developed, eight OPV campaigns were conducted to achieve and maintain high OPV3 coverage (figure 1). In the late 1970s, the campaigns consisted of one to three immunization rounds conducted over days and separated by an interval of6-8 weeks. After the first campaign, the estimated number ofpolio cases per 100,000 total population fell to 1.5 in When the campaigns were stopped in favor of strengthening routine immunization services in 1979, the incidence of polio immediately began to rise such that by the end of 1980, cases had returned to the pre-1976 level. This abrupt increase in cases, combined with a slower-thanexpected rise in routine immunization coverage, led to a resumption of the OPV campaigns on an annual basis from 1983 to In contrast to the 1970s, the incidence of polio did not increase following the cessation of the campaigns in 1987, primarily because high OPV3 coverage was being maintained through routine immunization services by that time (figure 2) (an acceleration of the national Expanded Programme on Immunization [EPI] in 1984 had led to a substantial infusion of resources to ensure that at least 80% of infants were being fully immunized by 1990). Between 1987 and 1992, the number of reported cases of polio remained relatively stable at per year. Wild poliovirus circulation continued to be widespread, however, as cases were still being reported from 70% of districts in The Poliomyelitis Eradication Program in Egypt: In 1989, President Hosni Mubarak declared that polio eradication would be a primary goal of the 1990s Decade of the Protection and Development ofthe Child in Egypt [15]. In July of that year, the Ministry of Health established a national polio eradication committee, and a "polio control room" was created in 1991 to coordinate activities. Four NIDs were undertaken between 1990 and 1994 to interrupt wild poliovirus transmission. In contrast to earlier campaigns, OPV3 coverage was already >90% and polio incidence was at an historic low (figure 2). During the NIDs, supplementary OPV doses were administered to all children <5 years old in 1990 and 1991 and <4 years old in 1993 and Because of the limited impact of a single NID round in 1990 and 1991, two rounds were conducted during the low season for poliovirus transmission in 1993 and 1994 (figure 1, table 1). Although poliovirus circulation was still widespread in Egypt by 1990, a decision was made to introduce geographically targeted mop-up campaigns in an attempt to accelerate the eradication program in the highest-risk districts. A total of three mop-up campaigns were conducted between 1991 and Immediate reporting and standardized investigation of all AFP cases began in August 1990, with an emphasis on the timely collection of 2 stool specimens for virologic studies and

3 SS8 Aylward et al. nn 1997; 175 (Supp1 1) Reported Cases of Polio OPV3 Coverage* 2,500, ,100% 2,000 80% 1,500 1,000 60%... 40% Key [J Polio Cases +OPV3 (%) Figure 2. Reported cases of poliomyelitis and infant immunization coverage with 3 doses of oral poliovirus vaccine (OPV3), Egypt, (nationwide Expanded Programme on Immunization was established in 1980). * Does not include supplementary doses given through national immunization days. 500 ~... H 11.: fi I 20% a 60-day follow-up examination for residual paralysis. In 1990, the National Institute for Vaccines and Sera in Cairo joinedthe Global Polio LaboratoryNetwork as a WHO regional reference laboratory. Beginning in January 1992, all health facilities were required to file a weekly "zero report" if no cases were seen (until 1987, national polio data consisted only ofcases reported from the National Polio Institute). A telex system was established to allow each governorate to send a daily AFP telex to the polio control.room in Cairo. By 1993, every reported AFP case had a laboratory investigation and every patient had a follow-up examination (table 2), and all polio cases were confirmed by virus isolation, residual paralysis, death, or loss to follow-up, rather than on the basis of one clinical examination. In 1991, authorities in Egypt recommended that children should receive a single dose of inactivated poliovirus vaccine (IPV) at 2 months of age because ofspeculation that suboptimal seroconversion was contributing to the continued widespread circulation of wild poliovirus [16]. As a result,,..., 1.5 million children received a dose of IPV in 1992 and in The single-dose IPV strategy was discontinued in 1994, however, because of financial constraints and concerns as to its efficacy. TheImpact of Polio Eradication Activities in Egypt Although the reported number of polio cases fell significantly following the OPV campaigns ofthe 1970s and the EPI acceler- Table 1. Selected characteristics of nationwide oral polio vaccine (OPV) immunization campaigns, ranked by associated reduction in cases, Egypt, % reduction Total Low' Weeks Target age Total doses in polio immunization season between group ofopv cases* rounds rounds rounds (months) (millions) , * % reduction in polio cases between 12-month periods immediately before and after end of each campaign (negative result indicates increase in reported cases). t High season for enterovirus circulation in Egypt is May-November.

4 JIO 1997;175 (Suppl1) Polio Eradication in Egypt S59 Reported Polio Cases 100r , Figure 3. Reported cases of poliomyelitis by month of onset, Egypt, lill *1993 OL l Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month ation of the 1980s, it was not until 1993 that there was a significant restriction in the geographic distribution ofthe virus [8]. In 1993, 150 polio cases were reported from 33% of the districts, compared with 584 cases from 69% of districts in The lack of a seasonal variation in polio incidence in 1993 also suggests that widespread circulation ofthe virus was interrupted in that year (figure 3). Despite further improvements in AFP surveillance, polio cases continued to decline, to 120 cases in 24% of districts in 1994 and 71 cases in 21% of districts in The recent progress toward polio eradication in Egypt seems primarily due to the NIDs that were conducted in 1993 and A number of factors distinguish these NIDs from previous campaigns (table 1). Compared with the campaigns of the 1970s and 1980s, the NIDs included newborns, were conducted when routine immunization was already > 85%, and were completed in a shorter period of time. In contrast to the NIDs of , the NIDs consisted of multiple rounds and, as op- Table 2. Improvement in performance of acute flaccid paralysis (AFP) case investigation as monitored with standard indicators, Egypt, Total AFP cases % reported within 48 h % investigated within 48 h of report % with ;:;,1 specimen collected % with 60-day follow-up examination posed to virtually all previous campaigns, both rounds were conducted in the low season for poliovirus circulation. In addition, the number of OPV doses administered per round in 1993 was much higher than in previous years, suggesting that the immunization coverage achieved was also substantially higher. The mop-up campaigns did not contribute significantly to the observed decline in polio. The reduction in cases among high-risk districts that did or did not conduct mop-ups was similar (78% and 78%, respectively, in 1991, and 29% and 27%, respectively, in 1992). In retrospect, it was very unlikely that these mop-ups could have interrupted polio transmission, as they were conducted in relatively small geographic areas while wild poliovirus circulation was still widespread [17]. Because only the highest-incidence districts were included in the mop-ups, the virus could have been readily reintroduced from contiguous low-incidence districts or other high-risk districts that were not identified because of poor surveillance. The addition of a single dose of IPV to the immunization schedule at 2 months of age probably did not playa substantial role in the interruption of poliovirus circulation. Based on the finding that only 50% of polio cases had received OPV3 in 1990 and 1992, the efficacy ofopv was estimated to be >90% [18]; cases were primarily due to a failure to vaccinate children rather than vaccine failure. The introduction of IPV in did not address this problem, and IPV probably reached the same infants as were already receiving OPV3. A comparison of confirmed and discarded polio cases for the period showed no difference in the proportion of children who had received IPV, after controlling for age, OPV history, and sex, suggesting that IPV at 2 months ofage conferred no additional protection (personal communication: Linkins R, CDC, Atlanta).

5 S60 Aylward et al. JID 1997; 175 (Suppl 1) Table 3. Expected and reported number of nonpolio acute flaccid paralysis (AFP) cases, by region, Egypt, Expected Reported 1994 Region (no. of population nonpolio nonpolio nonpolio governorates) (millions) AFP cases* AFP cases AFP rate Cairo area (3) Nile Delta (8) Upper Egypt (8) Other (8) Egypt (27) * Expected rate of nonpolio AFP is> 1 case/100,000 population < 15 years old. Current Priorities of the Polio Eradication Initiative At this point in the polio eradication program in Egypt, improved AFP surveillance and accurate diagnosis of cases are needed to confirm achievements and ensure that future supplementary immunization activities are properly targeted. The highest priority is to ensure that all cases ofafp, including nonpolio conditions such as Guillain-Barre syndrome, are reported and investigated. In 1994, the national nonpolio AFP rate was 0.34 cases/l00,000 population < 15 years old, substantially lower than the minimum expected rate of 1 caseiloo,ooo [9]. The lack ofnonpolio AFP cases in certain geographic areas indicates that surveillance must be improved to confirm the absence of polio (table 3). The low AFP rate is primarily due to a failure to report nonpolio paralytic conditions in children 5-15 years old. Improved reporting requires a closer working relationship between public health officials and clinicians and active surveillance to regularly search for AFP cases in the main hospitals of each governorate. The accuracy of polio diagnosis must also be improved. Intratypic differentiation should be performed on all poliovirus isolates to distinguish between wild and vaccine strains. Additional resources could then be allocated for supplementary immunization activities in areas where wild poliovirus is known to persist. NIDs must be conducted for at least another 2 years, after which the need for further nationwide OPV campaigns can be reassessed. Mopping up should only be conducted when the performance of AFP surveillance is sufficient to confirm that wild poliovirus transmission has been limited to focal geographic areas, if not interrupted completely. Lessons for Poliovirus-Endemic Countries The experience with implementing a polio eradication initiative in Egypt illustrates a number of important points for other poliovirus-endemic countries. First, achieving and sustaining high routine immunization coverage is an important determinant ofthe success ofnids; in the absence of a strong routine program, NIDs may need to be continued indefinitely. Second, high-quality NIDs must be the priority while wild poliovirus circulation remains widespread. Third, mop-up immunization should be reserved until there is high-quality AFP surveillance demonstrating that wild poliovirus circulation has become geographically restricted. Conclusions The recent progress toward polio eradication in Egypt demonstrates that wild poliovirus circulation can be interrupted in densely populated tropical countries with suboptimal sanitation if the globally recommended strategies are properly implemented. It is particularly important, however, that NIDs be of a consistently high quality in all geographic areas to stop widespread low-level poliovirus circulation. Establishing AFP surveillance provides a quantifiable means of monitoring progress and confirming achievements through the use of internationally standardized indicators. The ultimate success of the global polio eradication initiative does not require substantial modification of these strategies. Proper implementation of the existing strategies, however, in the few areas of the world in which poliomyelitis remains highly endemic is the key to the successful eradication of this disease. Acknowledgments We thank Nick Ward and Harry Hull (WHO), Steve Cochi (CDC), and Frank Cummings (Clark Atlanta University, Atlanta) for manuscript review. References 1. World Health Assembly. Global eradication of poliomyelitis by the year Geneva: World Health Organization, 1988; WHA resolution no. WHA Expanded Programme on Immunization. Certification of poliomyelitis eradication-the Americas, Wkly Epidemiol Rec 1994;69: Patriarca PA. Polio outbreaks: a tale of torment. Lancet 1994;344: Expanded Programme on Immunization. Poliomyelitis in Wkly Epidemiol Rec 1994;69: Robbins Fe. Eradication ofpolio in the Americas. lama 1993;270: Ward NA, Milstien JB, Hull HF, Hull BP. A global overview and hope for the eradication of poliomyelitis by the year Trop Geogr Med 1993;45: Expanded Programme on Immunization. Progress towards poliomyelitis eradication-egypt. Wkly Epidemiol Rec 1994;69: Centers for Disease Control and Prevention. Progress toward poliomyelitis eradication-egypt, MMWR Morb Mortal Wkly Rep 1993;43: Hull HF, Ward NA, Hull BP, Milstien JB, de Quadros e. Paralytic poliomyelitis; seasoned strategies, disappearing disease. Lancet 1994; 343: Wright PF, Kim-Farley RJ, de Quadros CA, et al. Strategies for the global eradication ofpoliomyelitis by the year N Engl 1 Med 1991;325:

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