.

Special Report

Strategies for the Certification of the Eradication of Wild Poliovirus Transmission in the Americas18

Because it appears that the last case of poliomyelitis caused by transmission of indigenous wild poliovirus occurred 2 years ago on 23 August 2992 in Peru, the chalienge for PAHO is to develop a methodology of certification that will convince the rest of the world that the eradication of poliomyelitis in the Americas has been achieved. To that end, the guidelines set forth here allow for a rigorous and stand- ardized evaluation of the certification process by objective experts. As it was during the campaign to eradicate smallpox, epidemiologic surveillance (of acute flaccid paralysis [Al?] in the case of polio) will be the most important component of the certification process. It must be demonstrated that when cases of AFP occur, they will be identified, reported, and investigated in a timely manner to insure that if wild poliovirus is present, it will be identified.

INTRODUCTION greater for poliomyelitis than it was for smallpox. On 6 July 1990, delegates to the first Nonetheless, the basic conditions that meeting of the International Certification were essential to certifying the eradica- Commission on Polio Eradication (ICCPE) tion of smallpox appear to be equally ap- established preliminary criteria for certi- plicable to polio eradication: fying that countries in the Americas are free of poliomyelitis (1-2). The Commis- sion recognized that it is extraordinarily no detection of wild poliovirus over difficult to demonstrate with certainty that an extended period of time, in the con- no wild polioviruses are circulating in a text of a surveillance system that is given country, let alone in the Region as good enough to detect both cases and a whole. The challenge is akin to that the virus, should they be present; experienced in certifying that smallpox a thorough country-by-country doc- had been eradicated, but it is even more umentation of program activities and difficult, because the ratio of asympto- findings; and, finally, matic infections to clinical cases is much the judgment by an independent in- ternational commission that suffi- cient evidence is available to support ‘Document prepared by the Expanded Program on Immunization, Pan American Health Organiza- the belief that poliovirus circulation tion, Washington, D.C., June 1993. has ceased.

Bulletin of PAHO 27(3), 2993 287 For certification purposes, good sur- for at least 3 years before it could be said veillance is the most important condition with reasonable certainty that eradication that must be met. Surveillance for polio had been achieved. cases encompasses surveillance for all The eventual interruption of indige- conditions causing acute flaccid paralysis nous wild virus transmission is possible (AFP) in persons under 15 years of age, because (1) there is no natural animal res- as well as for suspected polio cases among ervoir for wild poliovirus, (2) infected older persons. It must be demonstrated persons do not excrete the virus for more that when cases of AFP occur, they will than a few weeks, and (3) wild poliovirus be identified, reported, and investigated does not survive in the environment for in a timely manner to ensure that wild prolonged periods of time. Given the large poliovirus will be detected if it is present. number of inapparent infections that ex- The approach to the certification effort ist for every clinical case of the disease must be rigorous yet practical. Ulti- (6-8), measures in addition to case-find- mately, the information gathered must ing will be needed to detect circulating be adequate in quantity and quality to wild polioviruses. Accordingly, wild constitute convincing evidence before the poliovirus surveillance will include test- Commission and the world that trans- ing the stools of normal children and mission of indigenous wild poliovirus has sampling and testing community sewage indeed ceased in the Western Hemi- to help rule out transmission after the last sphere. culture-confirmed paralytic cases have As was the case during the certification been reported. of smallpox eradication, the process of certifying polio eradication will evolve, LESSONS LEARNED FROM requiring refinement at each step (3-4). CERTIFICATION OF SMALLPOX ERADICATION DEFINITION OF POLIOMYELITIS ERADICATION The smallpox eradication certification process in the Americas provided expe- The evolution of the certification pro- rience in four significant areas: (1) the cedures can be understood more readily amount of time that should elapse from by reviewing the definition of and the cri- the last case of paralytic disease to the teria for poliomyelitis eradication as de- point where one could confidently judge veloped by the Directing Council of PAHO that wild virus has ceased circulating, (2) in 1985 (5) and the ICCPE in 1990 (2). the comprehensiveness required of the The definition of polio eradication (as surveillance system, (3) the competence put forth by the Directing Council) is the and diligence needed from the official interruption of transmission of indige- certification committee reviewing na- nous wild poliovirus. Such transmission tional data, and (4) the level of political can and usually does occur as inapparent support that is called for to ensure com- infections. Paralytic cases (one per 100 to pliance with the certification criteria. one per 1 000 infections) serve as a vital First, experience during smallpox erad- indicator of continuing poliovirus spread; ication eventually showed that, with good because of this, their detection is critical. surveillance, no more than a year was At its first meeting in July 1990, members required to confirm that eradication had of the ICCPE decided that the Region been achieved. In practice, however, a should be free of any paralytic polio- 2-year interval was observed. Polio pre- myelitis due to wild poliovirus infection sents a more difficult problem owing to

288 Bulletin of PAHO 27(3), 1993 the occurrence of a large number of in- the first smallpox eradication certification apparent infections, so 3 years after the commission to be established was for last culture-confirmed case has been South America. It suffered from defects provisionally agreed upon as the time in both composition and performance. The period needed for certification of polio commission for smallpox eradication cer- eradication. tification in the Americas had few guide- Preliminary anaIysis of a mathematical lines and its assessment of the situation model developed for statistical validation was brief and not rigorous. Fortunately, of the eradication of indigenous wild subsequent history demonstrated that poliovirus in the Americas (Debanne et smallpox had indeed been eradicated from al., unpublished) indicates that the 3-year South America. This lack of rigor will not period of freedom from paralytic polio- be the case with polio certification be- myelitis may need to be extended to 4 cause the epidemioIogy of polio, i.e., years. The provisional results of this study asymptomatic transmission of the virus, suggest that with good AFP surveillance presents many more challenges to erad- and no detected culture-confirmed polio ication than did smalIpox. cases, the probability that wild poliovirus Finally, interest and efforts invested in would continue to circulate undetected the earlier certification process varied for more than 4 years is less than 5%. greatIy from country to country. Coun- This probability continues to decrease over tries from which smallpox had just been time. eradicated showed great interest in cer- Second, the quality of the surveillance tification, whereas those countries in system that operated during the small- which the disease had been eliminated pox eradication campaign was demon- many years before did not consider cer- strated by the comprehensiveness of the tification a high priority. In the Americas, reports of rash illness with fever and governments will have to mobilize ade- chicken pox cases once smallpox cases quate numbers of staff to prepare prop- had ceased to occur. These reports were erly for Region-wide certification of polio especially helpful in convincing members eradication. of certification committees that if small- Although details of the process may be pox virus had been circulating, it would modified as certification progresses, the have been detected and reported. Sur- essential features-adequate prepara- veillance for AFP serves this role in the tion, detailed documentation of the evi- polio program. dence of at least 3 years of freedom from For polio, as for smallpox, the shorter poliomyelitis, and the independence and the time that has eIapsed since the last authority of the certification team-must case, the more sensitive the surveillance remain unchanged throughout. program must be. As more time elapses, many hundreds of additional infections are needed to sustain chains of trans- CRITERIA FOR CERTIFICATION mission, with higher probabilities that in- OF POLIO ERADICATION fections will be detected if present. Also as with smallpox, areas of greatest inter- The measures to be taken are set forth est are highly populated areas, given that below (I): chains of infection are not readily sus- tained in sparsely populated, remote 1. Verification of the absence of virol- regions. ogidly confirmed indigenous polio- Third, as discussed by Fenner et al. (3), myelitis cases in the Americas for a

Special Report 289 period of at least 3 years under cir- However, this does not imply that cer- cumstances of adequate surveillance; tification should wait until global eradi- 2. Verification of the absence of de- cation has been achieved. As with small- tectable wild polioviruses from com- pox, the concept of eradication can apply munities as determined by testing to entire continents, such as the Ameri- of stools from normal children and, cas; but to be certified, each country’s where appropriate, testing of waste- surveillance system must be capable of water from high-risk populations; recognizing and containing importations 3. On-site evaluation by national cer- of wild poliovirus when they occur. tification commissions appointed jointly by PAHO and respective ROLE OF THE ICCPE member countries, composed of knowledgeable local persons and The ICCPE is composed of experts who outside experts. One or two respon- are critical in their assessments and whose sible ICCPE members will serve in judgment is respected both nationally and advisory roles during this process. internationally. Some of those selected After the national commission con- are experts in communicable disease con- siders that the criteria have been met, trol, others in virology or health man- the information will be submitted to agement. Some have also had the benefit the full ICCPE for final certification; of serving previously as members of var- 4. Establishment of appropriate meas- ious international smallpox certification ures to deal with the potential im- commissions. The membership is as fol- portation of cases from areas that lows: Dr. Waldyr Arcoverde, Brazil (later are not free of polio. replaced by Dr. Antonio Olinto of Brazil); Dr. Isao Arita, Japan; Dr. Rodrigo Guer- The first two recommendations com- rero, Colombia; Dr. Dorothy Horstmann, prise the foundation for the certification United States of America; Dr. Jan Kos- effort and are addressed in detail later in trzewski, Poland; Dr. Maureen Law, this report. Areas with cases that are clas- Canada; Dr. Elsa Moreno, Argentina; Dr. sified as “compatible” with polio-a cat- V. Ramalingaswami, India; Dr. Olikoye egory which indicates a failure in surveil- Ransome-Kuti, Nigeria; Dr. Frederick lance-wilI need adequate documentation Robbins, United States of America of special wild poliovirus surveillance and (Chairman); Dr. Guillermo Soberon, of house-to-house mop-up immunization Mexico; and Sir Kenneth Standard, Ja- campaigns. (See below for a full defini- maica. To prepare for certification of the tion of “compatible” and other surveil- eradication of poliomyelitis in the Amer- lance classifications of AFP.) icas, the ICCPE has met twice, the sec- The third recommendation will require ond meeting having taken place in March on-site evaluation of surveillance criteria 1992 in Rio de Janeiro, Brazil (9). and local conditions by the responsible The mode of operation of the ICCPE members of the ICCPE. has been established as follows: As pointed out in the fourth recom- mendation, even after certification, sur- 1. For each area of the Americas, one veillance will need to be continued in the or two ICCPE commissioners will Americas until polio has been eradicated have responsibility for overseeing from the rest of the world. As long as certification procedures. The seven other parts of the world remain infected, areas are the Southern Cone coun- the risk of importations will continue. tries, Brazil, the Andean countries, .

290 BuZIetin of PAHO 27(33), 1993 Central America, the countries of the so that alI countries can be appropriately Caribbean, Mexico, and Canada and recognized for their historic accomplish- the United States. ments. 2. Areas will be considered for certi- fication only if all their constituent NATIONAL STRATEGIES FOR countries have been free of polio- CERTIFICATION myelitis for a period of at least 3 years. All countries should now be Four strategies will be essential for engaged in the precertification pro- generating country reports that would cess of collecting and evaluating data justify certification by the ICCPE: (1) sur- from surveillance of AFP and wild veillance of AFP, (2) surveillance of wild poliovirus, as discussed below. poliovirus, (3) active AFP case searches 3. National commissions will be orga- in areas of poor surveiuance, such as areas nized in each country to review and where confirmed or compatible cases oc- oversee the precertification activi- curred in the past or where reports were ties of intensified surveillance for not received, and (4) documentation of AFP, active case searches in areas mass immunization campaigns in areas where surveillance is poor, surveil- of risk-such as those areas where con- lance of wild poliovirus, and im- firmed or polio-compatible cases have oc- munization campaigns in risk areas, curred. The final country report must e.g., areas where confirmed and provide accurate documentation of these compatible cases have occurred in activities. Simply put, the formula for the past. successful certification is: 4. Each country will prepare a national report to be reviewed by the re- [Adequate AFP Surveillance] + sponsible ICCPE commissioner that [Surveillance of Wild Poliovirus] + will serve to document the interrup- [Active Case Searches In Risk Areas] + tion of transmission of wild polio- [Mop-up Immunization Campaigns In Risk VhlS. Areas] = CERTIFICATION

Once preliminary approval of country Generally, the effectiveness of the re- reports has been achieved, the ICCPE will porting system for AFP will determine meet and review country presentations how prepared a country is to deal with for a final decision on each area’s status. importations of wild poliovirus. Coun- Ultimately, it will be the responsibility of tries wiI1 need to document what addi- the ICCPE to reach one of two conclu- tional measures have been taken to pre- sions: either that it is satisfied that trans- vent spread if importations do occur. mission has been interrupted, or that it would be satisfied if certain specific ad- Surveillance of AFP and Wild ditional measures were undertaken. Poliovirus Certification of eradication is possible only for the Hemisphere as a whole and To achieve poliomyelitis eradication, can only occur when the ICCPE has agreed PAHO has depended upon the following that transmission has been interrupted in basic program strategies: achievement and all countries. Because polio eradication is maintenance of high immunization levels such a tremendous achievement for the (which includes supplemental strategies countries of the Americas, the process of such as national immunization days and certification should receive high priority mop-up operations), effective surveil-

Special Report 291 lance to detect all new cases, and a rapid country. They attend regular meetings at response to the occurrence of new cases the national level where they are pro- (10-22). Surveillance is the most impor- vided with feedback via program evalu- tant component of the overall eradication ations and where they receive continuing strategy, because it corroborates that the medical education. ultimate goal of the program-zero cases Before 1990, cases of AFP were “con- of polio-has been achieved. Moreover, firmed’ as poliomyelitis if there was (a) it is an invaluable tool to monitor the laboratory confirmation (wild-type polio- impact of the program and permit the virus isolated from stools), (b) epidemi- assignment of resources to the most ologic linkage to another case of AFP or needed areas. to a confirmed case of poliomyelitis, (c) Surveillance systems vary from coun- residual paralysis 60 days after onset of try to country and even within countries. symptoms, (d) death, or (e) lack of fol- Nevertheless, some common principles low-up of a case. Cases of AFP were “dis- have been applied and implemented. At carded” as not being poliomyelitis if they least one reporting source for AFP was did not meet these criteria. To increase identified in each county or district (or the specificity of the case definition, be- comparable small geopolitical unit). Health ginning in 1990, a case of AFP was “con- centers are the primary reporting sources firmed” only if it was associated with wild- because cases of AFP are commonly en- type poliovirus isolation. Cases of AFP countered there for diagnosis, treatment, which could neither be confirmed nor or rehabilitation. Each reporting source is discarded-because two adequate stool required to report to the state, depart- specimens had not been collected, the mental, provincial, or national level every cases had resulted in residual paralysis week, whether AFP cases have occurred or death, or there had been no follow- or not. In turn, state officials report weekly up-were classified as cases “compati- to the national level, and national au- ble” with poliomyelitis. Specimens were thorities report weekly by fax or com- tested for viral isolation in three differ- puterized electronic mail to PAHO head- ent laboratories until 1991, when the quarters (13). recommendation was changed to two A “suspected’ polio case is any case laboratories. of acute paralysis in a person less than Special importance is given to collect- 15 years old for any reason other than ing two stool specimens within 2 weeks trauma, or paralytic illness in a person of after onset of paralysis because the like- any age in whom a diagnosis of polio- lihood of wild-type poliovirus isolation myelitis is possible. If the suspected case diminishes significantly when stool spec- is determined to have acute “flaccid’ pa- imens are collected later (14). ralysis, then the case is reclassified as In addition to collecting adequate stools “probable.” Epidemiologists attempt to from AFP cases, wild poliovirus surveil- investigate every case of AFP within 48 lance will also include stool surveys of hours after notification, in order to con- normal children (contact investigations) firm the clinical diagnosis and to obtain and sampling and testing of sewage (9, laboratory specimens. These epidemiol- 25-16; Tambini et al., in preparation). ogists have been specially trained by the Of the other methodologies available, Expanded Program on Immunization (EPI) lameness surveys (17-28) are impractical and are supervised by the national min- for most countries because of the large istry of health and the PAHO epide- number of persons required for an ade- miologist assigned to that particular quate sample and the difficulties in mak-

292 Bdletin of PAHO 27(3), 1993 ing an accurate etiologic diagnosis long tine1 site” where stools from normal chiI- after the onset of illness. Attempts to iso- dren would be colIected. The program late wild poliovirus from flies is likewise requirement to colIect stools from five deemed impractical. Poliovirus has been children who live in the same neighbor- isolated from flies around outbreaks of hood as an index AFP case is already in poliomyelitis, but the flies themselves place, but not all these specimens were harbor virus only up to 3 weeks after the processed in the laboratory. The previous last case of the outbreak (19-24). Finally, requirement to process stools from con- serosurveys for poliomyelitis neutraliz- tacts of only at-risk AFP cases (risk fac- ing antibodies are of little value because tors being age <6 years and the presence of the impossibility of discriminating of fever at paralysis onset) would be ex- antibodies formed in response to vaccine- panded to contacts of all AFP cases, re- related poliovirus from those formed in gardless of the presence of risk factors response to wild-type poliovirus (25). for confirmed poliomyelitis. This mea- While surveillance of wastewater for sure would ensure that approximately the presence of wild poliovirus is an ac- 10 000 additional stools would be pro- cepted strategy, it has inherent difficul- cessed each year. Since index cases of ties. High ambient temperatures and high AFI? that are not caused by wild polio- bacterial content of wastewater in tropi- virus appear more or less at random, the cal areas promote rapid inactivation of accumulation of this large volume of in- the poliovirus. Given that the predicted formation over 3-4 years (30 000-40 000 survival times of polioviruses under such specimens) would be important addi- conditions are short (the half-life for in- tional data for the ICCPE to use in de- fectivity is <2 days [26]), it is likely that ciding about the absence of transmission. most of the virus detected in wastewater The laboratory processing of stools of at represents what has been excreted from least five contacts per AFP case lessens children only a few days before sam- the need for testing and sampling of sew- pling. Its reliability in detecting the ex- age as a strategy for detecting transmis- istence of wild poliovirus is therefore lim- sion. However, sewage sampling and ited to the brief period during which the testing will be conducted in some se- virus is circulating in a community. A lected areas of the Americas (e.g., Bue- good AFP surveillance system, mean- nos Aires; Lima; the northeastern area of while, is not as time-sensitive, since it Brazil; Mexico City; Canada; and the detects the presence of wild poliovirus in United States). the community by identifying cases of With this background, the ICCPE has paralytic poliomyelitis. The importance indicated that every country’s surveil- of high-quality AFP surveillance infor- lance of AFP and wild poliovirus should mation, not only for the eradication of meet five key surveillance indicators: (1) wild poliovirus transmission but also for at least 80% of the all the health units the certification of this accomplishment, included in the reporting network should cannot be overemphasized. be reporting regularly each week; (2) the Accordingly, the ICCPE has recom- rate of AFP cases should be approxi- mended that for at least 80% of all cases mately 1.0 case reported per 100 000 pop- of AFP, the stools of five contact children ulation < 15 years of age; (3) at least 80% be collected and tested in the laboratory. of all AFP cases reported should be in- With surveillance of AFP in place, the vestigated within 48 hours of reporting; occurrence of a case of AFP in any given (4) at least 80% of all AFP cases reported area would make that area a proxy “sen- should have two stool specimens taken

Special Report 293 for virus culture within 2 weeks of pa- include establishing a “rumor register,” ralysis onset; and (5) at least 80% of all carrying out publicity campaigns, and AFP cases reported should have stool in- setting up a system for rewards. The re- vestigations of at least five contacts. ward system established by PAHO in 1988 has not been readily accepted in all coun- Active Case Searches in Areas of tries because some national health au- Poor Surveillance thorities fear that it would set a precedent with regard to the reporting of other dis- A country’s report should contain an eases. In fact, no evidence of this has account of active case searches in selected been found. Indeed, the smallpox expe- areas, using standardized methodolo- rience demonstrated that rewards were gies. In particular, it should include iden- an important adjuvant to other surveil- tification of risk areas, the questionnaire lance efforts. The smallpox rewards were employed, and analysis of the data initially small but were gradually in- collected. creased to a high of US$ 1 000 offered by WHO in 1978. At present the polio re- ward offered by PAHO/WHO is US$ 100. Mop-up Immunization Campaigns Serious consideration should be given to Directed at Areas of Risk increasing this reward, particularly in view of the approximately 2 years that have The ICCPE recognizes two important elapsed since the last culture-confirmed concerns regarding certification of polio polio case in the Americas was reported eradication in the countries. Some coun- in Junin, Peru, on 23 August 1991. Ec- tries as a whole may meet all five of the uador has already raised the reward to AFP surveillance indicators described US$ 1 000. above; but within the country, smaller Finally, border locations and areas with units, such as states, provinces, or dis- civil disorder, heavy migration, and ref- tricts, may not and thus will remain areas ugee populations should receive special of concern. A second worry pertains to attention. the so-called high-risk compatible cases Surveillance of AFP will spearhead which occurred within the last 4 years. PAHO’s efforts to certify that indigenous A PAHO investigation revealed that wild poliovirus transmission has been among AFP cases, the ones most likely eradicated from the Americas. To that end, to be polio were those among children all countries must demonstrate that when less than 6 years of age who experienced cases of AFP occur, they will be identi- fever at the onset of paralysis (24, 27). fied, reported, and investigated in a timeIy Special mop-up immunization cam- manner to ensure that wild poliovirus will paigns in areas where such cases oc- be recognized if it is present. Until global curred are important. Accordingly, spot eradication is gained, much work still maps of these high-risk compatible cases needs to be done to maintain the appar- have been prepared. Reports (to be in- ent polio-free status that has been achieved corporated in the certification document) in the Western Hemisphere. should be prepared describing the num- ber of children under 5 years of age tar- geted for immunization, number or per- REFERENCES Gentage immunized with OPV, and 1. Pan American Health Organization. Final number of households visited. report: Zst meeting of the International Com- Other certification strategies that should mission forthe Certification ofthe Eradication be highlighted in a country’s final report ofPolio in the Americas. Washington, DC:

294 Bulletin of PAHO 27(3), 1993 PAHO; July 1990. (Ref dot EPI/TAG9/ 14. Andrus JK, de Quadros CA, and Olive 914). J-M. The surveillance challenge: final stages 2. de Quadros CA, Andrus JK, Olive J-M, of eradication of poliomyelitis in the Macedo CG de, Henderson DA. Polio Americas. MMWR. 1992;41(no SS-l):Zl- eradication from the Western Hemi- 26. sphere. Annu Rev Public Health. 1992;13:239- 15. Pan American Health Organization. Final 252. report of the first informal consultation on en- 3. Fenner F, Henderson DA, Arita I, et al. vironmental sampling and testing procedures Smallpox and ifs eradication. 1st ed. Geneva: for wild poliovirus in the Americas. Wash- World Health Organization; 1988. ington, DC: PAHO; February 1991. (Ref 4. Breman JG, Arita I. The confirmation and dot EPI/TAG10/92-4). maintenance of smallpox eradication. N 16. Pan American Health Organization. Final Engl J Med. 1980;303:1263-1273. report of the second informal consultation on 5. Pan American Health Organization. Di- environmental sampling and testing proce- rector announces campaign to eradicate dures for wild poliovirus in the Americas. poliomyelitis from the Americas by 1990. Washington, DC: PAHO; February 1992. Bull Pan Am Health Organ. 1985;19:213-215. (Ref dot EPIiTAG10/92-5). 6. Melnick JL. Poliomyelitis virus in urban 17. Bender RH. Some observations on polio- sewage in epidemic and in nonepidemic myelitis lameness surveys. Rev Infect Dis. times. Am J Hyg. 1947;45:240-253. 1984;6(suppl 2):371-375. 7. Melnick JL, Ledinko N. Development of 18. Heymann DL. House-to-house and school neutralizing antibodies against the three lameness surveys in Cameroon: a com- types of poliomyelitis virus during an ep- parison of two methods for estimating idemic period: the ratio of inapparent in- prevalence and annual incidence of par- fection to clinical poliomyelitis. Am ] Hyg. alytic poliomyelitis. Rev Infect Dis. 1984; 1953;58:207-222. 6(suppl 2):376-378. 8. Melnick JL, Walton M, Isacson I’, Card- 19. Paul JR, Trask JD, Bishop MB, Melnick well W. Environmental studies of en- JL, Casey AE. The detection of polio- demic enteric virus infections: I. Com- myelitis virus in flies. Science. 1941;94:395- munity seroimmune patterns and 396. poliovirus infection rates. Am J Hyg. 1957; 20. Trask JD, Paul JR, Melnick JL. The detec- 65:1-28. tion of poliomyelitis virus in flies collected 9. Pan American Health Organization. Final during epidemics of poliomyelitis: I. report: IOfh Technical Advisory Group Meet- Methods, results, and types of flies in- ing on Vaccine-preventable Diseases and 2nd volved. 1 Exp Med. 1943;77:531-544. Infernal Meeting of the International Certz)?- 21. Sabin AB, Ward R. Insects and epide- cation Commission of Poliomyelitis Eradica- miology of poliomyelitis. Science. 1942; tion in the Americas. Rio de Janeiro: PAHO; 95:300-301. March 1992. (Ref dot EPUTAG10/92-1). 22. Toomey JA, Takacs WS, Tischer LA. 10. Pan American Health Organization. Plan Poliomyelitis virus from flies. PYOCSot Exp of action for the eradication of indigenous Biol Med. 1941;48:637-639. fransmission wild poliovirus from the Amer- 23 of Melnick JL, Ward R. Susceptibility of vervet icas by 1990. Washington, DC: PAHO; June ’ monkeys to poliomyelitis virus in flies col- 1988. (Document CElOl/B). lected at epidemics. Jlnfect Dis. 1945;77:249- 11. Hinman AR, Foege WH, de Quadros CA, 252. et al. The case for global eradication of 24 poliomyelitis. Bull WorldHealfh Organ. 1987; . Francis T Jr, Brown GC, Penner LR. Search 65:835-840. for extrahuman sources of poliomyelitis virus. JAMA. 1948;136:1088-1092. 12. de Quadros CA, Andrus JK, Olive J-M, et al. Eradication of poliomyelitis: prog- 25. Pan American Health Organization. Final ress in the Americas. Pediafr Infect Dis 1. reporf, 7th Meeting of the Technical Adviso y 1991;10:222-229. Group on EPl and fhe Eradication of Polio- 13. Pan American Health Organization. Polio myelitis in the Americas. Cartagena: PAHO; eradication field guide. 2nd ed. Washington, 1989. (Ref dot EPUTAG7/89-1). DCPAHO; 1988:1-53. (Technical paper 26. Hurst CJ, Benton WH, McClellan KA. no 6). Thermal and water source effects upon

Special Report 295 the stability of enteroviruses in surface Hull HF. Screening for acute flaccid pa- freshwaters. Can 1 Microbial. 1989;35:474- ralysis for polio eradication: ways to im- 480. prove specificity. Bull World Healfk Organ. 27. Andrus JK, de Quadros CA, Olive J-M, 1992;70(5):591-596.

ANNOUNCEMENT

1994 Award in Honor of Fred 1. Soper (1893-l 976) for Publications in the Field of Inter-American Health

This is a call for submission of nominations for the 1994 award in honor of Fred L. Soper, former Director (from 1947 to 1958) of the Pan American Health Organization, Regional Office of the World Health Organization for the Americas. In addition to his service with PAHO/WHO, Dr. Soper played a major role in the fight against yellow fever and other infectious diseases in Brazil, as part of his work with the Rockefeller Foundation in the 1920s and 193Os, and in the control of typhus in North Africa and Italy during the Second World War. He was one of the truly major figures in inter-American health in this century.

The award is presented annually to the author or authors of an original scientific contribution containing new information on, or insights into, the broad field of public health, with special relevance to Latin America, the Caribbean, or both. This work may be a report, an analysis of new data (experimental or observational), or a new approach to analyzing available data. Preference is given to studies involving more than one discipline and to papers related to infectious disease, a life-long concern of Dr. Soper.

Only papers published during calendar year 1993 in Latin American scientific journals listed in the index Medicus or in the official journals of the Pan American Health Organization are eligible for consideration for the 1994 award. Furthermore, the award is limited to works by authors whose principal affiliation is with teaching, research, or service institutions located in the countries of Latin America and the Caribbean (including the Centers of the Pan American Health Organization).

The Award Fund is administered by the Pan American Health and Education Foundation (PAHEF), which receives voluntary contributions designated for the purpose and holds them in a separate fund. The award consists of a certificate and a monetary prize of US$ 400.00. Each year’s winner(s) are nominated by an Award Committee, composed of representatives designated by PAHO and by PAHEF; final selection is made by the Board of Trustees of PAHEF.

Papers meeting the above criteria and submitted by or on behalf of their authors may be considered for the Fred L. Soper Award. All submissions must be received by 31 March 1994 at the following address:

Executive Secretary PAHEF 525 Twenty-third Street, N.W. Washington, D.C. 20037 U.S.A.

296 Bulletin of PAHO 27(3), 1993