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Progress toward poliomyelitis eradication in Kano State, Nigeria, 2010 - 2017
research-article
Author(s):
Suleiman Haladu Ahmed
1
,
&
,
,
Patrick Nguku
1 ,
Saheed Oluwatoyin Gidado
1 ,
Musa Kalamullah Bawa
2 ,
Usman Lawan Shehu
2 ,
Amina Abdullahi
1 ,
Ramatu Usman Obansa
1 ,
Kabir Ibrahim Getso
2 ,
Mohammd Nasir Mahmoud
2 ,
Imam Wada Bello
2 ,
Yahaya Musa Sharif
2 ,
Bashir Abba
3 ,
Sani Umar
3 ,
Ndadilnasiyya Endie Waziri
1 ,
Chima Ohunabunwo
4
Publication date (Electronic):
12 November 2021
Journal:
The Pan African Medical Journal
Publisher:
The African Field Epidemiology Network
There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
Introduction
Kano State in Northern Nigeria was a major source of Wild Polio Virus (WPV) cases in Nigeria up until 2015. In 2009, the State reported 168 WPV cases out of the 388 reported nationally. This paper characterizes the progress made by Kano State in polio eradication.
Methods
In December 2017, we conducted a descriptive review of Routine Immunization (RI) from both the District Vaccine Data Management Tool (DVD-MT) and District Health Information System (DHIS2) from 2010 to 2017. Also, we reviewed the Acute Flaccid Paralysis (AFP) and Supplementary Immunization Activities (SIAs) data reported for Kano State from 2010 to 2017. Also, we obtained the number of reported WPV cases by serotypes.
Results
From 2010 to 2017, a total of 65 confirmed WPV cases were reported in Kano State. Of these, 58 (89%) were WPV1 and 7 (11%) WPV3. Almost half of these cases were reported in 2012 from 14 LGAs. The number of reported cases fell to 15 (23%) in 10 LGAs in 2013, and further decreased to 5 (8%) in four LGAs in 2014. No new WPV cases have been detected in Kano since 2015. During the same period, 23 circulating Vaccine Derived Polio Viruses (cVDPV2) cases were reported in Kano. Specifically, 10 LGAs reported 10 cases in 2011. Three LGAs reported three cases in 2012, while eight LGAs reported 10 total cases in 2014. During the 2010 to 2017 period 61 SIAs were conducted.
Most cited references14
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Possible Eradication of Wild Poliovirus Type 3 — Worldwide, 2012
Olen M. Kew, Stephen Cochi, Hamid Jafari … (2014)
In 1988, the World Health Assembly resolved to eradicate polio worldwide. Since then, four of the six World Health Organization (WHO) regions have been certified as polio-free: the Americas in 1994 (1), the Western Pacific Region in 2000 (2), the European Region in 2002 (3), and the South-East Asia Region in 2014 (4). Currently, nearly 80% of the world’s population lives in areas certified as polio-free. Certification may be considered when ≥3 years have passed since the last isolation of wild poliovirus (WPV) in the presence of sensitive, certification-standard surveillance (1–4).* Although regional eradication has been validated in the European Region and the Western Pacific Region, outbreaks resulting from WPV type 1 (WPV1) imported from known endemic areas were detected and controlled in these regions in 2010 and 2011, respectively (5). The last reported case associated with WPV type 2 (WPV2) was in India in 1999, marking global interruption of WPV2 transmission (6). The completion of polio eradication was declared a programmatic emergency for public health in 2012, and the international spread of WPV1 was declared a public health emergency of international concern in May 2014. The efforts needed to interrupt all indigenous WPV1 transmission are now being focused on the remaining endemic countries: Nigeria, Afghanistan, and Pakistan. WPV type 3 (WPV3) has not been detected in circulation since November 11, 2012. This report summarizes the evidence of possible global interruption of transmission of WPV3, based on surveillance for acute flaccid paralysis (AFP) and environmental surveillance. Poliovirus Surveillance Since the launch of the Global Polio Eradication Initiative in 1988, progress toward eradication has been tracked by detection and investigation of AFP cases and testing of stool specimens for polioviruses by accredited laboratories of the WHO Global Polio Laboratory Network (7). AFP surveillance has been supplemented by environmental surveillance (i.e., testing of sewage samples) in 25 countries, including Pakistan, since 2009, Nigeria since 2011, and Afghanistan since 2013 (7). Environmental surveillance often can detect evidence of WPV infections even in the absence of AFP cases, which is especially important for detection of WPV3, whose case-to-infection ratio (approximately one paralytic case in 1,000 infections) is about one fifth that of WPV1 (approximately one in 200) (8). The quality of AFP surveillance is monitored with performance indicators for detection sensitivity and investigation timeliness (7). WPV3 Cases No WPV3 cases have been detected globally since November 2012 (Figure 1). The latest WPV3 in Asia was isolated from a child aged 1 year in the Federally Administered Tribal Area of Pakistan who had onset of AFP on April 18, 2012, and the latest environmental WPV3 isolate in Asia was from a sample collected in Karachi, Pakistan, on October 7, 2010. The latest WPV3 in Africa was isolated from an infant aged 11 months in Yobe, Nigeria, who had onset of paralysis on November 10, 2012, and the latest environmental WPV3 isolate in Africa was from a sample collected in Lagos, Nigeria, on November 11, 2012. The number of countries reporting WPV3 cases changed from five in 2001, to 12 in 2008, to seven in 2010, and to two in 2012 (Figure 1). During 2010–2013, the number of WPV3 isolated globally in stool specimens collected from AFP patients declined from 87 to zero, whereas the number of AFP cases with specimens tested increased from 98,788 in 2010 to 101,701 in 2013. The genetic diversity of WPV3 isolates has fallen steadily worldwide since 1988. The number of distinct WPV3 genotypes (≥15% nucleotide sequence divergence) detected globally declined from 17 in 1988, to five in 2001, to three in 2010, and to two in 2012 (Figure 2). In Pakistan, WPV3 clusters (approximately 5% nucleotide sequence divergence) within genotypes declined from four in 2010, to one in 2011, and to one in 2012. In Nigeria, the number of WPV3 clusters declined from nine in 2010, to six in 2011, and to two in 2012. Discussion WPV3 has not been detected since November 2012, suggesting that global WPV3 transmission has been interrupted. In regions and areas where the transmission of all three indigenous WPV serotypes has been interrupted, the order of disappearance was first WPV2, then WPV3, and then WPV1. The rapidly declining genetic diversity of WPV3 isolates during the last decade is consistent with progress toward eradication and was observed during a period of improving surveillance performance in Pakistan and Nigeria, the two countries which harbored the last known WPV3 reservoirs (5,7). The possible interruption of WPV3 transmission is a historic milestone for the Global Polio Eradication Initiative and demonstrates that full implementation of the national emergency action plans† in the three remaining polio-endemic countries (Pakistan, Afghanistan, and Nigeria) will also interrupt WPV1 transmission. If validated, the eradication of WPV3 would mark the third time that transmission of a distinct human pathogen (the others are smallpox virus and WPV2) has been interrupted through immunization. The last isolation of WPV2 occurred 15 years ago from a case with onset in October 1999 (6). In the pre-vaccine era, WPV3 had a worldwide distribution (Figure 2). Although WPV3, for reasons unknown, is less able than WPV1 to spread over wide geographic areas and cause explosive outbreaks, long-range WPV3 exportations and regional outbreaks have occurred (5,9). The substitution of bivalent oral poliovirus vaccine (types 1 and 3) for monovalent oral poliovirus vaccines and trivalent oral poliovirus vaccine (types 1, 2, and 3) in supplementary immunization activities in late 2009 led to the rapid collapse of WPV3 transmission in India the following year, and to the steady decline of WPV3 detection elsewhere (4,5). Continued sensitive surveillance is needed before the evidence of WPV3 eradication is conclusive, particularly given evidence of remaining limitations of surveillance in Pakistan, Nigeria, and elsewhere (7). The low case-to-infection ratio for WPV3 infections requires higher surveillance sensitivity for detection than that required for WPV1. However, the case-to-infection ratio is lowest for WPV2 (8), and no reappearance has been detected since 1999. High levels of population immunity to poliovirus type 3 should be maintained, both to protect against any residual WPV3 infections and to prevent the emergence and spread of type 3 circulating vaccine-derived polioviruses, a rare event (10). What is already known on this topic? Four of the six World Health Organization regions have been certified as polio-free: the Americas in 1994, the Western Pacific Region in 2000, the European Region in 2002, and the South-East Asia Region in 2014. The last detection of wild poliovirus type 2 was in 1999. What is added by this report? No type 3 wild poliovirus (WPV3) infections have been detected globally since November 2012, suggesting that transmission might have been interrupted. The number of countries reporting WPV3 isolates declined from seven in 2010 to zero in 2013. During 2010–2013, the number of WPV3 isolated globally in stool specimens collected from patients with acute flaccid paralysis declined from 87 to zero, whereas the number of acute flaccid paralysis cases with specimens tested increased from 98,788 in 2010 to 101,701 in 2013. What are the implications for public health practice? Transmission of WPV3 might be interrupted worldwide. Continued sensitive surveillance is needed before the evidence of WPV3 eradication is conclusive, particularly given evidence of limitations of surveillance in Pakistan, Nigeria, and elsewhere.
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Contribution of Environmental Surveillance Toward Interruption of Poliovirus Transmission in Nigeria, 2012–2015
Background. Cases of paralysis caused by poliovirus have decreased by >99% since the 1988 World Health Assembly's resolution to eradicate polio. The World Health Organization identified environmental surveillance (ES) of poliovirus in the poliomyelitis eradication strategic plan as an activity that can complement acute flaccid paralysis (AFP) surveillance. This article summarizes key public health interventions that followed the isolation of polioviruses from ES between 2012 and 2015. Methods. The grap method was used to collect 1.75 L of raw flowing sewage every 2–4 weeks. Once collected, samples were shipped at 4°C to a polio laboratory for concentration. ES data were then used to guide program implementation. Results. From 2012 to 2015, ES reported 97 circulating vaccine-derived polioviruses (cVDPV2) and 14 wild polioviruses. In 2014 alone, 54 cVDPV type 2 cases and 1 WPV type 1 case were reported. In Sokoto State, 58 cases of AFP were found from a search of 9426 households. A total of 2 252 059 inactivated polio vaccine and 2 460 124 oral polio vaccine doses were administered to children aged <5 year in Borno and Yobe states. Conclusions. This article is among the first from Africa that relates ES findings to key public health interventions (mass immunization campaigns, inactivated polio vaccine introduction, and strengthening of AFP surveillance) that have contributed to the interruption of poliovirus transmission in Nigeria.
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Surveillance to Track Progress Toward Polio Eradication — Worldwide, 2016–2017
Tracie Gardner, Ousmane Diop, Jaume Jorba … (2018)
Global efforts to eradicate polio began in 1988, and four of the six World Health Organization (WHO) regions currently have achieved poliofree certification. Within the remaining two regions with endemic poliomyelitis (African and Eastern Mediterranean), Afghanistan, Nigeria, and Pakistan have never interrupted transmission of wild poliovirus (WPV). The primary means of detecting poliovirus transmission is surveillance for acute flaccid paralysis (AFP) among children aged 1 year, it is difficult to determine if transmission of WPV1 persists in pockets of the population where polio surveillance is infeasible or limited (e.g., in insurgent-controlled and inaccessible areas) ( 5 ). One cVDPV case was reported in AFR during 2016, a cVDPV type 2 (cVDPV2) case from Nigeria. During 2017, a total of 22 cVDPV cases were reported in AFR, all cVDPV2 cases from the Democratic Republic of the Congo (Table 1). Among the 20 countries evaluated in AFR, 14 (70%) met both national surveillance indicators in 2017, compared with 12 (60%) in 2016. All three Ebola-affected countries had NPAFP rates ≥2 during 2016 and 2017. In 2016 only Guinea also achieved ≥80% stool adequacy; however in 2017, Guinea and Liberia both achieved ≥80% stool adequacy. TABLE 1 National and subnational acute flaccid paralysis surveillance indicators and number of confirmed wild poliovirus and circulating vaccine-derived poliovirus cases, by country, for all countries with poliovirus transmission during 2011–2017 and those that were affected by the Ebola virus disease outbreak in West Africa — World Health Organization African Region and Eastern Mediterranean Region, 2016–2017* WHO Region/Country No. of AFP cases (all ages) Regional/National NPAFP rate† % Subnational areas with NPAFP rate ≥2§ % Regional or national AFP cases with adequate specimens¶ % Subnational areas with ≥80% adequate specimens % Population living in areas meeting both indicators** No. of confirmed WPV cases* No. of confirmed cVDPV cases*,†† 2016 AFR (all 47 countries)§§ 31,759 7.4 NA 92 NA NA 4 1 Angola 392 3.5 94 94 100 84 —¶¶ —¶¶ Cameroon 868 7.8 100 87 90 82 — — Central African Republic*** 143 7.0 100 73 29 25 — — Chad 484 7.2 87 85 65 78 — — Côte d'Ivoire 371 4.2 85 94 85 74 — — DRC*** 1,819 5.1 100 78 50 56 — — Equatorial Guinea 3 0.6 0 0 0 0 — — Ethiopia*** 1,048 2.5 82 79 46 9 — — Gabon*** 43 6.1 100 26 10 3 — — Guinea 1,061 20.1 100 88 88 85 — — Kenya 554 2.8 89 89 79 70 — — Liberia 69 3.6 100 75 53 43 — — Madagascar 791 7.6 96 86 77 80 — — Mali 307 3.8 89 90 78 96 — — Mozambique 425 3.2 90 82 40 59 — — Niger*** 366 3.5 75 62 13 3 — — Nigeria 17,867 20.7 97 99 97 99 4 1 Republic of the Congo 82 3.6 83 82 67 78 — — Sierra Leone 68 2.6 100 77 50 45 — — South Sudan 323 6.3 90 91 80 70 — — EMR (all 21 countries)††† 15,951 7.6 NA 90 NA NA 33 1 Afghanistan 2,905 20.1 100 92 97 100 13 — Iraq 605 4.2 90 81 58 44 — — Pakistan 7,848 12.6 100 87 88 99 20 1 Somalia 316 5.9 100 99 100 100 — — Syria 246 3.2 57 81 64 33 — — Yemen 715 7.1 100 91 100 100 — — 2017 AFR§§ 30,889 7.1 NA 92 NA NA — 22 Angola 411 3.6 94 97 100 84 — — Cameroon 973 8.9 100 85 90 82 — — Central African Republic 167 8.3 100 80 43 48 — — Chad*** 702 10.2 100 79 52 62 — — Côte d'Ivoire 334 3.6 60 91 75 58 — — DRC*** 2,113 5.8 100 79 46 42 — 22 Equatorial Guinea 12 3.7 57 17 14 0 — — Ethiopia 1,096 2.6 73 86 100 90 — — Gabon*** 51 6.9 100 59 50 35 — — Guinea 453 8.4 100 87 100 100 — — Kenya 463 2.2 66 84 72 53 — — Liberia 81 4.1 100 82 60 76 — — Madagascar 701 6.6 100 93 96 99 — — Mali 256 3.1 100 88 89 95 — — Mozambique 374 2.9 100 86 70 80 — — Niger*** 681 6.4 100 70 0 0 — — Nigeria 15,967 18.5 97 98 97 99 — — Republic of the Congo 118 5.5 83 84 58 66 — — Sierra Leone*** 75 2.8 100 77 75 77 — — South Sudan 388 7.3 90 85 70 67 — — EMR††† 19,035 9.0 NA 88 NA NA 22 74 Afghanistan 3,090 21.3 100 94 100 100 14 — Iraq 699 4.8 95 87 79 74 — — Pakistan 10,196 16.3 100 86 100 100 8 — Somalia 345 6.3 100 99 100 100 — — Syria*** 348 3.6 57 70 57 28 — 74 Yemen 713 7.0 100 82 70 68 — — Abbreviations: AFP = acute flaccid paralysis; AFR = African Region; cVDPV = circulating vaccine-derived poliovirus; DRC = Democratic Republic of the Congo; Ebola = Ebola virus disease; EMR = Eastern Mediterranean Region; NA = not available; NPAFP = nonpolio AFP; WHO = World Health Organization; WPV = wild poliovirus. * Data current as of February 22, 2018. † Per 100,000 persons aged <15 years per year. § For all subnational areas regardless of population size. ¶ Standard WHO target is adequate stool specimen collection from ≥80% of AFP cases, assessed by timeliness and condition. For this analysis, timeliness was defined as two specimens collected ≥24 hours apart (≥1 calendar day in this data set), and both within 14 days of paralysis onset. Good condition was defined as arrival of specimens in a WHO-accredited laboratory with reverse cold chain maintained and without leakage or desiccation. ** Percentage of the country’s population living in subnational areas which met both surveillance indicators (NPAFP rates ≥2 per 100,000 persons aged <15 years per year and ≥80% of AFP cases with adequate specimens). †† cVDPV was associated at least one case of AFP with evidence of transmission and genetically linked. Guidelines for classification of cVDPV can be found at http://polioeradication.org/wp-content/uploads/2016/09/Reporting-and-Classification-of-VDPVs_Aug2016_EN.pdf. §§ Algeria, Angola, Benin, Botswana, Burkina Faso, Burundi, Cameroon, Cabo Verde, Central African Republic, Chad, Comoros, Côte d’Ivoire, Democratic Republic of the Congo, Equatorial Guinea, Eritrea, Ethiopia, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Lesotho, Liberia, Madagascar, Malawi, Mali, Mauritania, Mauritius, Mozambique, Namibia, Niger, Nigeria, Rwanda, Republic of the Congo, Sao Tome and Principe, Senegal, Seychelles, Sierra Leone, South Africa, South Sudan, Swaziland, Togo, Uganda, Tanzania, Zambia, and Zimbabwe. ¶¶ Dashes indicate that no confirmed cases were found. *** Stool adequacy dropped to <80% when stool condition was included with timeliness. ††† Afghanistan, Bahrain, Djibouti, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Morocco, Oman, Pakistan, Qatar, Saudi Arabia, Somalia, Sudan, Syria, Tunisia, United Arab Emirates, and Yemen. Among the 21 EMR countries, 15,951 AFP cases were reported in 2016, and 19,035 in 2017. Two EMR countries (Afghanistan and Pakistan) reported WPV1 cases in 2016 (33) and 2017 (22). The number of WPV1 cases reported by Afghanistan remained constant (13 in 2016 and 14 in 2017); the number reported from Pakistan declined from 20 (2016) to eight (2017). In 2016, one cVDPV2 case was reported in EMR, in Pakistan. In contrast, during 2017, 74 cVDPV cases were reported from EMR. All cases were type 2 and occurred in Syria; the most recent case occurred in September 2017 (Table 1), resulting in the largest cVDPV2 outbreak since the synchronized global cessation of use of type 2 oral poliovirus vaccine in April 2016 ( 6 ). Among the six countries evaluated in EMR, five met both national surveillance indicators in 2017, compared with all six in 2016 (Table 1). Although overall performance improved in 2017, national-level surveillance indicators masked suboptimal surveillance performance at subnational levels in both regions, (Table 1) (Figure). FIGURE Combined performance indicators for the quality of acute flaccid paralysis surveillance in subnational areas (states and provinces) of 26 countries that had poliovirus transmission during 2011–2017 or were affected by the Ebola outbreak in West Africa during 2014–2015 — World Health Organization African and Eastern Mediterranean Regions, 2017* ,† Abbreviations: AFP = acute flaccid paralysis; NPAFP = nonpolio AFP. * The Global Polio Eradication Initiative has set the following targets for countries with current or recent wild poliovirus transmission and their states/provinces: 1) NPAFP detection rate of ≥2 cases per 100,000 persons aged <15 years per year and 2) adequate stool specimen collection from ≥80% of AFP cases, with specimen adequacy assessed by timeliness and condition. Timeliness was defined as two specimens collected ≥24 hours apart (≥1 calendar day) and both within 14 days of paralysis onset. Good condition was defined as specimens arriving without leakage or desiccation in a maintained reverse cold chain at a World Health Organization-accredited laboratory. † Data are for AFP cases with onset during 2017, reported as of February 22, 2018. The figure above is a map showing combined performance indicators for the quality of acute flaccid paralysis surveillance in subnational areas (states and provinces) of 26 countries in the World Health Organization African and Eastern Mediterranean Regions that had poliovirus transmission during 2011–2017 or were affected by the Ebola outbreak in West Africa during 2014–2015. Environmental Surveillance Sewage sample testing supplements AFP surveillance by identifying poliovirus transmission that might occur in the absence of detected AFP cases ( 3 , 6 ). Environmental surveillance collection sites increased in Afghanistan, Nigeria, and Pakistan, from 21 in 2011 to 143 in 2017. As part of the Global Polio Eradication Initiative’s global environmental surveillance expansion plan, environmental surveillance is conducted in 91 sites in 38 countries without recent active WPV transmission, including 16 countries on the African continent. In Nigeria, sewage sampling is currently conducted at 70 sites in 18 states and the Federal Capital Territory. No WPV has been isolated since May 2014, and cVDPV2 was last detected in Borno state in March 2016. In Afghanistan, environmental sampling is conducted at 20 sites in nine provinces; five of the 20 sites were added in 2017. WPV1 from four genetic clusters was detected in samples collected among five provinces in 2017. In Pakistan, sampling is conducted at 53 sites in five provinces, including the Islamabad Capital Territory; two of the 53 sites were added in 2017. In 2017, 13% of samples were positive for WPV1, compared with 11% in 2016. WPV1 was detected in all five provinces in 2017. Environmental sampling was established in Mogadishu, Somalia, in October 2017, and two of the first three samples collected yielded cVDPV2 isolates. Global Polio Laboratory Network GPLN consists of 146 poliovirus laboratories located in the six WHO regions that are subject to a WHO-led quality assurance program. GPLN member laboratories follow standardized protocols to 1) isolate and identify poliovirus, 2) conduct intratypic differentiation (ITD) to identify WPV or screen for Sabin (vaccine) poliovirus and VDPV ( 7 ), and 3) conduct genomic sequencing. Sequencing results help monitor pathways of poliovirus transmission by comparing the nucleotide sequence of the VP1-coding region of poliovirus isolates. To meet standard laboratory timeliness indicators for processing a stool specimen, laboratories should report ≥80% of poliovirus isolation results within 14 days of specimen receipt, ≥80% of ITD results within 7 days of isolate receipt, and ≥80% of sequencing results within 7 days of ITD result. The standard combined field and laboratory performance indicator is to report ITD results for ≥80% of isolates within 60 days of paralysis onset in AFP cases. This indicator considers the entire interval from paralysis onset to specimen testing (EMR countries use a 45-day timeliness standard). The accuracy and quality of testing at GPLN laboratories is monitored through an annual accreditation program of onsite reviews and proficiency testing. During 2017, an accreditation checklist, including standard laboratory timeliness indicators for sewage sample processing, was implemented for laboratories conducting environmental surveillance. GPLN tested 218,478 stool specimens from patients with AFP in 2016 and 201,546 in 2017. WPV1 was isolated from 37 AFP case samples in 2016 and 22 AFP case samples in 2017. In addition, cVDPV was detected from 11 AFP cases in 2016 and 96 in 2017. GPLN laboratories met timeliness indicators for poliovirus isolation in all regions (Table 2). The overall timeliness indicator for onset to ITD results was met in all regions in both years. TABLE 2 Number of poliovirus isolates from stool specimens of persons with acute flaccid paralysis and timeliness of virus isolation and intratypic differentiation* reporting, by World Health Organization region — worldwide, 2016–2017 † WHO region/Year No. of specimens No. of poliovirus isolates % Poliovirus isolation results on time** % ITD resultswithin 7 days of laboratory receipt†† % ITD results within 60 days of paralysis onset Wild Sabin§ cVDPV¶ African 2016 65,520 4 4,771 4 95 94 97 2017 65,245 0 1,663 22 97 80 98 Americas 2016 1,920 0 18 0 84 92 91 2017 1,755 0 14 0 83 100 100 Eastern Mediterranean 2016 31,928 33 1,612 1 94 98 98 2017 35,602 22 2,521 74 98 99 97 European 2016 3,606 0 71 0 82 100 86 2017 3,480 0 73 0 83 92 90 South-East Asia 2016 101,550 0 5,247 2 98 99 99 2017 82,292 0 2,251 0 91 96 99 Western Pacific 2016 14,196 0 253 4 96 98 96 2017 13,370 0 140 0 96 97 90 Total§§ 2016 218,478 37 11,972 11 96 97 98 2017 201,546 22 6,662 96 94 91 98 Abbreviations: cVDPV = circulating vaccine-derived poliovirus; ITD = intratypic differentiation; PV = poliovirus; PV1 = PV type 1; PV2 = PV type 2; VDPV = vaccine-derived poliovirus; WHO = World Health Organization. * ITD is used to identify Sabin (vaccine) and non–Sabin-like poliovirus and screen for VDPV. † Data current as of February 28, 2018. § Either 1) concordant Sabin-like results in ITD test and VDPV screening or 2) ≤1% VP1 nucleotide sequence difference compared with Sabin vaccine virus (≤0.6% for VP2). ¶ For poliovirus types 1 and 3, ≥10 VP1 nucleotide differences from the respective poliovirus; for poliovirus type 2, ≥6 VP1 nucleotide differences from Sabin PV2. ** Results reported within 14 days of receipt of specimen. †† Results of ITD reported within 7 days of receipt of specimen. §§ For the last three indicators, total represents weighted mean percentage of regional performance. Overall genetic diversity declined among WPV1 isolates in 2017. In 2017, South Asia (SOAS) genotype was the only WPV1 genotype circulating globally and was detected in Afghanistan and Pakistan. West Africa B1 (WEAF-B1) genotype was last detected in Nigeria in 2016. Sequence analysis associated with the SOAS genotype indicates that WPV1 cases might have been missed by AFP surveillance in 2017; orphan WPV1 isolates (those with less genetic relatedness [≤98.5% in VP1 gene] to other circulating viruses) were associated with three of 22 WPV1 cases reported from Afghanistan and Pakistan, indicating possible gaps in AFP surveillance. In 2017, cVDPV viruses with extended divergence from the parental Sabin strain were also isolated from stool specimens of AFP cases and from environmental samples in three countries. Discussion The number of reported WPV cases declined to the lowest point ever in 2017; however, reported cVDPV cases increased from 2016 to 2017 because of major cVDPV2 outbreaks in the Democratic Republic of the Congo and Syria. Although most national-level surveillance quality indicators improved in 2017, considerable variation exists at subnational levels, particularly in inaccessible areas, and timely detection of circulating polioviruses can be hampered if active surveillance efforts are not rigorous. Repeated detection of WPV and cVDPV from sewage samples in locations where poliovirus cases have not been detected or where sewage detections have preceded detection in persons can provide early evidence of viral circulation within a community (e.g., WPV isolation in Pakistan during 2017) ( 8 ). Strategies to strengthen AFP surveillance in areas where conflict occurs have included increased AFP case searches among camps for internally displaced persons, engagement of community members in inaccessible areas, and active case searches in newly accessible areas ( 5 ). Although conflict might limit access to standard health facility–based surveillance, community-based surveillance has been effective in finding AFP cases, providing some assurance of the absence of poliovirus circulation in critical areas. For example, in Somalia, community volunteers have been instrumental in reporting AFP cases in inaccessible and partially accessible areas ( 9 ). The findings in this report are subject to at least two limitations. First, security-related issues, issues associated with mobile and difficult-to-access populations, or other factors that affect surveillance performance could affect interpretation of AFP surveillance indicators. Second, high NPAFP rates do not necessarily imply sensitive surveillance, because a proportion of reported AFP cases might not be actual AFP cases, and not all actual AFP cases might be detected. Certification of poliofree status requires at least 3 years of timely and sensitive poliovirus surveillance ( 10 ), including timely stool specimen collection and timely and appropriate transport of specimens to the laboratory. In 2017, specimen condition was a concern in Chad, DRC, Gabon, Niger, Sierra Leone, and Syria. Use of mobile technologies to improve timeliness and accuracy of AFP reporting in geographically hard-to-reach areas might be useful in some countries when linked with vigorous specimen collection (5). Strong supervision and monitoring of surveillance performance, especially at subnational levels, is important to achieve high-quality surveillance that can detect poliovirus transmission. Environmental surveillance has been an important supplement to AFP surveillance and, when carefully conducted in populations covered by sewage networks, can improve detection of circulating virus, particularly in high-risk areas with suboptimal AFP surveillance ( 3 ). Polio surveillance efforts need to reach geographically difficult-to-access and security-compromised areas and mobile and migrant populations. Surveillance data should be assessed routinely to identify suboptimal data quality. The need for strong poliovirus surveillance will continue beyond certification of eradication, until well after the use of all oral poliovirus vaccine has stopped globally. Poliovirus surveillance will need to be integrated with surveillance of other vaccine-preventable diseases to sustain capacity and maintain sufficient performance quality. As long as polioviruses continue to circulate in any country, all countries remain at risk. Summary What is already known about this topic? Surveillance is the cornerstone of polio eradication efforts. What is added by this report? In 2017, 22 wild poliovirus cases were reported from two countries (Afghanistan and Pakistan), the fewest number ever reported globally. Polio cases caused by circulating vaccine-derived polioviruses increased from four in 2016 to 96 in 2017 because of large outbreaks in Syria and the Democratic Republic of the Congo. Although surveillance performance indicators are improving at the national level, gaps remain, including at subnational levels. What are the implications for public health practice? As polio cases decline, sensitive and timely surveillance becomes even more important. As long as polioviruses circulate in any country, all countries remain at risk.
Author and article information
Contributors
Suleiman Haladu Ahmed:
https://orcid.org/0000-0002-7295-0000
Musa Kalamullah Bawa:
https://orcid.org/0000-0002-0360-4526
Amina Abdullahi:
https://orcid.org/0000-0002-4731-1805
Imam Wada Bello:
https://orcid.org/0000-0003-0792-2748
Bashir Abba:
https://orcid.org/0000-0002-9238-9812
Journal
Journal ID (nlm-ta): Pan Afr Med J
Journal ID (iso-abbrev): Pan Afr Med J
Journal ID (publisher-id): PAMJ
Title:
The Pan African Medical Journal
Publisher:
The African Field Epidemiology Network
ISSN
(Electronic):
1937-8688
Publication date
(Electronic):
12
November
2021
Publication date Collection: 2021
Volume: 40
Issue: Suppl 1
Electronic Location Identifier: 9
Affiliations
Author notes
[&
]
Corresponding author: Suleiman Haladu Ahmed, African Field Epidemiology Network, Abuja, Nigeria.
asuleiman@
123456afenet.net
Article
Publisher ID: PAMJ-SUPP-40-1-9DOI: 10.11604/pamj.supp.2021.40.1.19318
PMC ID: 9474848
SO-VID: b988392c-b39f-46d0-8aa7-aad692d8481b
Copyright © ©Suleiman Haladu Ahmed et al.
License:
The Pan African Medical Journal (ISSN: 1937-8688). This is an Open Access article distributed under the terms of the Creative Commons Attribution International 4.0 License ( https://creativecommons.org/licenses/by/4.0/ ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
History
Date
received
: 30
May
2019
Date
accepted
: 13
February
2020
Categories
Subject:
Research
ScienceOpen disciplines: Medicine