Wild Poliovirus Transmission Research Articles

Surveillance Systems to Track Progress Toward Polio Eradication - Worldwide, 2015-2016.

Global measures to eradicate polio began in 1988; as of 2014, four of six World Health Organization (WHO) regions have been certified polio-free. Within the two endemic regions (African and Eastern Mediterranean), Nigeria, Afghanistan, and Pakistan have never interrupted transmission of wild poliovirus (WPV) (1). The primary means of detecting poliovirus transmission is surveillance for acute flaccid paralysis (AFP) among children aged <15 years, combined with collection and testing of stool specimens from persons with AFP for detection of WPV and vaccine-derived polioviruses (VDPVs) (viruses that differ genetically from vaccine viruses and can emerge in areas with low vaccination coverage and cause paralysis) in WHO-accredited laboratories within the Global Polio Laboratory Network (2,3). AFP surveillance is supplemented by environmental surveillance for polioviruses in sewage from selected locations (4). Genomic sequencing of the VP1-coding region of isolated polioviruses enables mapping transmission by time and place, assessment of potential gaps in surveillance, and identification of the emergence of VDPVs. This report presents poliovirus surveillance data from 2015 and 2016, with particular focus on 20 countries in the African Region and six in the Eastern Mediterranean Region that reported WPV or circulating VDPVs (cVDPVs) during 2011-2016, as well as the three countries most affected by the 2014-2015 Ebola virus disease (Ebola) outbreak (Guinea, Liberia, and Sierra Leone). During 2016, 12 (60%) of the 20 African Region countries and all six of the Eastern Mediterranean Region countries met both surveillance quality indicators (nonpolio AFP rates of ≥2 per 100,000 persons aged <15 years per year and ≥80% of AFP cases with adequate stool specimens [stool adequacy]) at the national level; however, provincial-level variation was seen. To complete and certify polio eradication, surveillance gaps must be identified and surveillance activities, including supervision, monitoring, and specimen collection and handling, further strengthened.

Continued Endemic Wild Poliovirus Transmission in Security-Compromised Areas - Nigeria, 2016.

On August 10, 2016, 2 years after the most recent wild poliovirus (WPV) case was reported in Nigeria (in July 2014) (1), two WPV cases were reported in the northeastern state of Borno, which has been severely affected by insurgency-related insecurity since 2013. On September 9 and 26, 2016, two additional WPV cases were reported in Borno in children whose families migrated from security-compromised, inaccessible areas of the state. All four cases were WPV serotype 1 (WPV1), with genetic differences indicating prolonged undetected transmission. A large-scale emergency response plan was developed and implemented. The plan initially called for vaccination of 815,791 children during August 15-18 in five local government areas (LGAs) in the immediate vicinity of the first two WPV cases. Subsequently, the plan was expanded to regionally synchronized supplementary immunization activities (SIAs), conducted during August 27-December 6 in five Lake Chad basin countries at increased risk for national and regional WPV1 transmission (Cameroon, Central African Republic, Chad, Niger, and Nigeria). In addition, retrospective searches for missed cases of acute flaccid paralysis (AFP), enhanced environmental surveillance for polioviruses, and polio surveillance system reviews were conducted. Prolonged undetected WPV1 transmission in Borno State is a consequence of low population immunity and severe surveillance limitations associated with insurgency-related insecurity and highlights the risk for local and international WPV spread (2). Increasing polio vaccination coverage and implementing high-quality polio surveillance, especially among populations in newly secured and difficult-to-access areas in Borno and other Lake Chad basin areas are urgently needed.

Long-term evaluation of mucosal and systemic immunity and protection conferred by different polio booster vaccines.

Oral polio vaccine (OPV) and Inactivated Polio Vaccine (IPV) have distinct advantages and limitations. IPV does not provide mucosal immunity and introduction of IPV to mitigate consequences of circulating vaccine-derived polio virus from OPV has very limited effect on transmission and OPV campaigns are essential for interrupting wild polio virus transmission, even in developed countries with a high coverage of IPV and protected sewer systems. The problem is magnified in many countries with limited resources. Requirement of refrigeration for storage and transportation for both IPV and OPV is also a major challenge in developing countries. Therefore, we present here long-term studies on comparison of a plant-based booster vaccine, which is free of virus and cold chain with IPV boosters and provide data on mucosal and systemic immunity and protection conferred by neutralizing antibodies.Mice were primed subcutaneously with IPV and boosted orally with lyophilized plant cells containing 1 μg or 25 μg polio viral protein 1 (VP1), once a month for three months or a single booster one year after the first prime. Our results show that VP1-IgG1 titers in single or double dose IPV dropped to background levels after one year of immunization. This decrease correlated with >50% reduction in seropositivity in double dose and <10% seropositivity in single dose IPV against serotype 1. Single dose IPV offered no or minimal protection against serotype 1 and 2 but conferred protection against serotype 3. VP1-IgA titers were negligible in IPV single or double dose vaccinated mice. VP1 antigen with two plant-derived adjuvants induced significantly high level and long lasting VP1-IgG1, IgA and neutralizing antibody titers (average 4.3–6.8 log2 titers). Plant boosters with VP1 and plant derived adjuvants maintained the same level titers from 29 to 400 days and conferred the same level of protection against all three serotypes throughout the duration of this study. Even during period, when no plant booster was given (∼260 days), VP1-IgG1 titers were maintained at high levels. Lyophilized plant cells expressing VP1 can be stored without losing efficacy, eliminating cold chain. Virus-free, cold-chain free vaccine is ready for further clinical development.

Analysis of acute flaccid paralysis surveillance in Ethiopia, 2005-2015: progress and challenges.

IntroductionEthiopia joined the global effort to eradicate polio in 1996, and interrupted indigenous wild poliovirus transmission by December 2001. However, the country experienced numerous separate importations during 2003-2013. Sensitive Acute Flaccid (AFP) surveillance is critical to rule out undetected circulation of WPV and VDPVs.MethodsIn this study described, we used a retrospective descriptive study design to characterize the surveillance performance from 2005 to 2015.ResultsThe none-polio AFP rate improved from 2.6/100,000 children <15 years old in 2005 to 3.1 in 2015, while stool adequacy has also improved from 78.5% in 2005 to 92 % in 2015. At the national level, most AFP surveillance performance indicators are achieved and maintained over the years, however, AFP surveillance performance at sub-national level varies greatly particularly in pastoralist regions. In addition, the minimum standard for non-polio enterovirus isolation rate (10%) was not achieved except in 2007 and 2009. Nevertheless, the proportion of cases investigated within 2 days of notification and the proportion of specimens arriving in good condition within 3 days to the laboratory were maintained throughout all the years reviewed.ConclusionWe found that the AFP surveillance system was efficient and progressively improved over the past 10 years in Ethiopia. However, the subnational AFP surveillance performance varies and were not maintained, particularly in pastoralist regions, and the non-polio enterovirus isolation rate declined since 2010. We recommend the institution of community-based surveillance in pastoralist regions and conduct detail review of the laboratory sensitivity and the reverse cold chain system.

Progress Toward Poliomyelitis Eradication - Afghanistan, January 2015‒August 2016.

Only 74 cases of wild poliovirus (WPV) were reported globally in 2015, the lowest number of cases ever reported worldwide (1,2). All of the reported cases were WPV type 1 (WPV1), the only known WPV type still circulating; WPV type 2 has been eradicated, and WPV type 3 has not been detected since November 2012 (1). In 2015 in Afghanistan, WPV detection also declined from 2014, and trends observed in 2016 suggest that circulation of the virus is limited to a few localized areas. Despite the progress, there are concerns about the ability of the country's Polio Eradication Initiative (PEI) to meet the goal of interrupting endemic WPV transmission by the end of 2016 (3). The deteriorating security situation in the Eastern and Northeastern regions of the country considerably limits the ability to reach and vaccinate children in these regions. Furthermore, because of frequent population movements to and from Pakistan, cross-border transmission of WPV1 continues (4). Although the national PEI has taken steps to improve the quality of supplementary immunization activities (SIAs),* significant numbers of children living in accessible areas are still being missed during SIAs, and routine immunization services remain suboptimal in many parts of the country. This report describes polio eradication activities and progress in Afghanistan during January 2015‒August 2016 and updates previous reports (5,6). During 2015, a total of 20 WPV1 cases were reported in Afghanistan, compared with 28 cases in 2014; eight cases were reported during January‒August 2016, compared with nine cases reported during the same period in 2015. To achieve interruption of poliovirus transmission in Afghanistan, it is important that the 2016-2017 National Emergency Action Plan† for polio eradication be systematically implemented, including 1) improving the quality of SIAs and routine immunization services, 2) ensuring ongoing dialogue between PEI leaders and local authorities, 3) adopting innovative strategies for reaching children in security-compromised and inaccessible areas, and 4) strengthening cross-border coordination of polio vaccination and surveillance activities with Pakistan.

Polio Eradication in India: The Lessons Learned.

* Abbreviations: GPEI — : Global Polio Eradication Initiative OPV — : oral polio vaccine WPV — : wild polio virus India completed a full 5 years as a “polio-free nation” on January 13, 2016.1 It was a remarkable feat considering the odds against achieving this status. The Global Polio Eradication Initiative (GPEI) considered India to be the most difficult region of the world to eliminate wild polio virus (WPV) transmission and then maintain that status for 5 years. Significantly, India borders on Pakistan, which is still experiencing intense WPV circulation.2 India’s progress in becoming polio-free was a great confidence booster for all the stakeholders of the GPEI. The many lessons learned during this arduous exercise are helping strategists, program managers, and health workers of other countries still grappling with uninterrupted WPV transmission. India, a vastly diverse country with a 27 million birth cohort, undertook the largest vaccination drive against WPV in the world. With high population density, poor civic infrastructure, poor sanitation, an almost nonexistent public health system, rampant malnutrition and diarrhea, difficult-to-reach locales, high population mobility, and extremely high force of WPV transmission in few states,3 the interruption of WPV transmission was extremely difficult and demanding. The interplay of these challenging factors provided a perfect milieu for the WPV to circulate, and the prospect of achieving … Address correspondence to: Naveen Thacker, MBBS, MD, Deep Children Hospital & Research Center, Gandhidham, Kutch, Gujarat, India, PIN 370201. E-mail: drnaveenthacker{at}gmail.com

A spatial model of Wild Poliovirus Type 1 in Kano State, Nigeria: calibration and assessment of elimination probability

BackgroundSince the launch of the Global Polio Eradication Initiative, all but three countries (Nigeria, Pakistan, and Afghanistan) have apparently interrupted all wild poliovirus (WPV) transmission, and only one of three wild serotypes has been reported globally since 2012. Countrywide supplemental immunization campaigns in Nigeria produced dramatic reduction in WPV Type 1 paralysis cases since 2010 compared to the 2000’s, and WPV1 has not been observed in Nigeria since July 24, 2014. This article presents the development and calibration of a spatial metapopulation model of wild poliovirus Type 1 transmission in Kano State, Nigeria, which was the location of the most recent WPV1 case and 5 out of 6 of the reported WPV1 paralytic cases in Nigeria in 2014.MethodsThe model is calibrated to data on the case counts and age at onset of paralysis from 2003–2009. The features of the data drive model development from a simple susceptible-exposed-infective-recovered (SEIR) model to a spatial metapopulation model featuring seasonal forcing and age-dependent transmission. The calibrated parameter space is then resampled, projected forward, and compared to more recent case counts to estimate the probability that Type 1 poliovirus has been eliminated in Kano state.ResultsThe model indicates a 91 % probability that Type 1 poliovirus has been eliminated from Kano state as of October 2015. This probability rises to >99 % if no WPV1 paralysis cases are detected for another year. The other states in Nigeria have experienced even longer case-free periods (the only other state with a WPV1 case was Yobe, on April 19, 2014), and Nigeria is the last remaining country in Africa to experience endemic WPV1 transmission, so these results can be interpreted as an upper bound on the probability that WPV1 transmission is currently interrupted continent-wide.ConclusionsWhile the results indicate optimism that WPV1 transmission has been interrupted in Kano state, the model also assumes that frequent SIAs with high coverage continue to take place in Kano state through the end of the certification period. We conclude that though WPV1 appears to be on the brink of continent-wide elimination (WHO officially removed Nigeria from the list of polio-endemic countries on September 25, 2015), it is important for the polio program to maintain vigilance in surveillance and vaccination activities to prevent WPV1 resurgence through the WHO’s 3-year eradication certification period.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-1817-3) contains supplementary material, which is available to authorized users.

Environmental Isolation of Circulating Vaccine-Derived Poliovirus After Interruption of Wild Poliovirus Transmission - Nigeria, 2016.

In September 2015, more than 1 year after reporting its last wild poliovirus (WPV) case in July 2014 (1), Nigeria was removed from the list of countries with endemic poliovirus transmission,* leaving Afghanistan and Pakistan as the only remaining countries with endemic WPV. However, on April 29, 2016, a laboratory-confirmed, circulating vaccine-derived poliovirus type 2 (cVDPV2) isolate was reported from an environmental sample collected in March from a sewage effluent site in Maiduguri Municipal Council, Borno State, a security-compromised area in northeastern Nigeria. VDPVs are genetic variants of the vaccine viruses with the potential to cause paralysis and can circulate in areas with low population immunity. The Nigeria National Polio Emergency Operations Center initiated emergency response activities, including administration of at least 2 doses of oral poliovirus vaccine (OPV) to all children aged <5 years through mass campaigns; retroactive searches for missed cases of acute flaccid paralysis (AFP), and enhanced environmental surveillance. Approximately 1 million children were vaccinated in the first OPV round. Thirteen previously unreported AFP cases were identified. Enhanced environmental surveillance has not resulted in detection of additional VDPV isolates. The detection of persistent circulation of VDPV2 in Borno State highlights the low population immunity, surveillance limitations, and risk for international spread of cVDPVs associated with insurgency-related insecurity. Increasing vaccination coverage with additional targeted supplemental immunization activities and reestablishment of effective routine immunization activities in newly secured and difficult-to-reach areas in Borno is urgently needed.

Modeling the spread of polio in an IPV-vaccinated population: lessons learned from the 2013 silent outbreak in southern Israel.

BackgroundPolio eradication is an extraordinary globally coordinated health program in terms of its magnitude and reach, leading to the elimination of wild poliovirus (WPV) in most parts of the world. In 2013, a silent outbreak of WPV was detected in Israel, a country using an inactivated polio vaccine (IPV) exclusively since 2005. The outbreak was detected using environmental surveillance (ES) of sewage reservoirs. Stool surveys indicated the outbreak to be restricted mainly to children under the age of 10 in the Bedouin population of southern Israel. In order to curtail the outbreak, a nationwide vaccination campaign using oral polio vaccine (OPV) was conducted, targeting all children under 10.MethodsA transmission model, fitted to the results of the stool surveys, with additional conditions set by the ES measurements, was used to evaluate the prevalence of WPV in Bedouin children and the effectiveness of the vaccination campaign. Employing the parameter estimates of the model fitting, the model was used to investigate the effect of alternative timings, coverages and dosages of the OPV campaign on the outcome of the outbreak.ResultsThe mean estimate for the mean reproductive number was 1.77 (95 % credible interval, 1.46–2.30). With seasonal variation, the reproductive number maximum range was between zero and six. The mean estimate for the mean infectious periods was 16.8 (8.6–24.9) days. The modeling indicates the OPV campaign was effective in curtailing the outbreak. The mean estimate for the attack rate in Bedouin children under 10 at the end of 2014 was 42 % (22–65 %), whereas without the campaign the mean projected attack rate was 57 % (35–74 %). The campaign also likely shortened the duration of the outbreak by a mean estimate of 309 (2–846) days. A faster initiation of the OPV campaign could have reduced the incidence of WPV even if a lower coverage was reached, at the risk of prolonging the outbreak.ConclusionsOPV campaigns are essential for interrupting WPV transmission, even in a developed country setting with a high coverage of IPV. In this setting, establishing ES of WPV circulation is particularly crucial for early detection and containment of an outbreak.Electronic supplementary materialThe online version of this article (doi:10.1186/s12916-016-0637-z) contains supplementary material, which is available to authorized users.

Progress Toward Polio Eradication - Worldwide, 2015-2016.

In 1988, the World Health Assembly resolved to eradicate poliomyelitis. Wild poliovirus (WPV) transmission persists in only two countries (Afghanistan and Pakistan) after the removal of Nigeria from the list of countries with endemic polio in September 2015.* Indigenous WPV type 2 has not been detected since 1999 and was declared eradicated by the Global Commission for the Certification of Poliomyelitis Eradication in September 2015.(†) Since November 2012, when the last case of WPV type 3 was detected in Nigeria, WPV type 1 has been the sole circulating type of WPV (1). This report summarizes global progress toward polio eradication during 2015-2016 and updates previous reports (2). In 2015, 74 WPV cases were reported in two countries (Afghanistan and Pakistan), a decrease of 79% from the 359 WPV cases reported in 2014 in nine countries; 12 WPV cases have been reported in 2016 (to date), compared with 23 during the same period in 2015 (3). Paralytic polio caused by circulating vaccine-derived poliovirus (cVDPV) remains a risk in areas with low oral poliovirus vaccine (OPV) coverage. Seven countries, including Pakistan, reported 32 cVDPV cases in 2015 (4). In four of these countries, ≥6 months have passed since the most recent case or isolate. One country (Laos) with VDPV transmission in 2015 has reported three additional cVDPV cases in 2016 to date. Encouraging progress toward polio eradication has been made over the last year; however, interruption of WPV transmission will require focus on reaching and vaccinating every missed child through high quality supplementary immunization activities (SIAs) and cross-border coordination between Afghanistan and Pakistan (5,6).

Surveillance Systems to Track Progress Toward Polio Eradication — Worldwide, 2014–2015

Global efforts to eradicate polio began in 1988, and polio-free certification has been achieved in four of the six World Health Organization (WHO) regions. Nigeria was removed from WHO's list of countries with endemic polio in September 2015, achieving an important milestone toward interruption of wild poliovirus (WPV) transmission in the African Region (1). Afghanistan and Pakistan, both in the Eastern Mediterranean Region, were the only countries to report WPV cases in 2015. Previously reported outbreaks caused by WPV importation during 2013-2014 have ended (2,3). The primary means for detecting poliovirus transmission is surveillance for acute flaccid paralysis (AFP) among children aged <15 years (4,5). Stool specimens collected from children with AFP are tested for both WPV and vaccine-derived poliovirus (VDPV) in WHO-accredited laboratories within the Global Polio Laboratory Network (GPLN). In selected locations, AFP surveillance is supplemented with environmental surveillance (testing sewage for poliovirus) (6). Testing of stool and sewage samples includes genomic sequencing to characterize poliovirus isolates; results are used to map poliovirus transmission and identify gaps in AFP surveillance. This report presents poliovirus surveillance data from 2014 and 2015, focusing on the 20 countries in the African Region and six in the Eastern Mediterranean Region that reported a WPV or circulating VDPV (cVDPV) case during 2011-2015, including Guinea, Liberia, and Sierra Leone, which were most affected by the 2014-2015 Ebola virus disease (Ebola) outbreak.

Integrated human and animal vaccination delivery to Nomadic Fulani communities in Northern Nigeria 2015

Background: Nigeria remains the only African country yet to interrupt transmission of wild polio virus and has a high incidence of childhood vaccine preventable diseases. Routine immunization (RI) services have not achieved sufficient coverages in remote rural settings especially among nomadic Fulani pastoralist. The high mobility and dispersion of these pastoralists makes easily missed by healthcare services yet these pastoralist often seek medical care for their animals regardless of the cost. We adopted an integrated human and animal vaccination strategy with the aim of increasing access and demand for RI services among nomadic pastoralist. Methods & Materials: Nomadic communities and stock routes in Bauchi were identified and geocoded using GPS enabled phones. We assessed RI and animal vaccination coverage in these communities. Three rounds of targeted joint human and animal vaccination campaigns were carried out. Vaccinations and other healthcare services were administered to children, women of child bearing age, cattle and dogs. Vaccination teams were composed of local veterinary officers, healthcare workers and health promotion officials. Results: A total of 4285 children less than one year of age and 1624 women were vaccinated in 49 settlements. Vaccination coverage increased from 22.7% to 80.1%. Of the 1271 children given oral polio vaccine (OPV) and 836 given pentavalent vaccine, 311(24.5%) and 348(41. 6%) respectively were zero dose. Dropout rate was 42%. A total of 496(30.5%) women that received Tetanus Toxoid (TT) received it for the first time. The animal component of the study gave intervention to a total of 28581 cattle increasing the coverage from 41% to 61%, 26 dogs were vaccinated against rabies. Conclusion: Routine immunization coverage increased in these communities largely due to the administration of human vaccinations alongside animal vaccination and other healthcare services. High dropout rate recorded can be attributed to the high mobility of these pastoralists. We recommend that the government adopt this strategy in nomadic pastoralist communities.

Importation and outbreak of wild polioviruses from 2000 to 2014 and interruption of transmission in Cameroon

BackgroundEfficient implementation of the global eradication strategies consisting of Acute Flaccid Paralysis (AFP) surveillance and mass immunization campaigns led to interruption of indigenous wild poliovirus transmission in Cameroon in 1999. ObjectivesThis study describes type 1 and type 3 wild poliovirus (WPV) importation, incidence, geographic distribution and control since the original interruption of transmission in Cameroon. Study designStool samples from AFP patients under the age of 15 years in Cameroon were collected nationwide and subjected to virus isolation on RD and L20B cell cultures. Resulting virus isolates were typed by intratypic differentiation (ITD) and analysis of the VP1 coding sequence of the viral genome. Surveillance data originating from Cameroon between 2000 and 2014 were considered for retrospective descriptive analyses. ResultsFrom 2003 to 2009, multiple WPV importation events from neighboring countries affected mainly in the northern regions of Cameroon but did not led to sustained local transmission. Throughout this period, 16 WPV1 and 5 WPV3 were detected and identified as members of multiple clusters within type-specific West Africa B genotypes (WEAF-B). In 2013–2014, a polio outbreak associated to a highly evolved (“orphan”) WPV1 affected four southern regions of Cameroon. ConclusionsThe appearance of highly evolved lineage of type 1 WPV suggests potential surveillance gap and underscore the need to maintain comprehensive polio immunization activities and sensitive surveillance systems in place as long as any country in the world remains endemic for WPV.

Strategic Engagement of Technical Surge Capacity for Intensified Polio Eradication Initiative in Nigeria, 2012-2015.

Background. Following the 65th World Health Assembly (WHA) resolution on intensification of the Global Poliomyelitis Eradication Initiative (GPEI), the Nigerian government, with support from the World Health Organization (WHO) and other partners, implemented a number of innovative strategies to curb the transmission of wild poliovirus (WPV) in the country. One of the innovations successfully implemented since mid 2012 is the WHO's engagement of surge capacity personnel.Methods. The WHO reorganized its functional structure, adopted a transparent recruitment and deployment process, provided focused technical and management training, and applied systematic accountability framework to successfully manage the surge capacity project in close collaboration with the national counterparts and partners. The deployment of the surge capacity personnel was guided by operational and technical requirement analysis.Results. Over 2200 personnel were engaged, of whom 92% were strategically deployed in 11 states classified as high risk on the basis of epidemiological risk analysis and compromised security. These additional personnel were directly engaged in efforts aimed at improving the performance of polio surveillance, vaccination campaigns, increased routine immunization outreach sessions, and strengthening partnership with key stakeholders at the operational level, including community-based organizations.Discussion. Programmatic interventions were sustained in states in which security was compromised and the risk of polio was high, partly owing to the presence of the surge capacity personnel, who are engaged from the local community. Since mid-2012, significant programmatic progress was registered in the areas of polio supplementary immunization activities, acute flaccid paralysis surveillance, and routine immunization with the support of the surge capacity personnel. As of 19 June 2015, the last case of WPV was reported on 24 July 2014. The surge infrastructure has also been instrumental in building local capacity; supporting other public health emergencies, such as the Ebola outbreak response and measles and meningitis outbreaks; and strengthening the integrated disease surveillance and response. Due to weak health systems in the country, it is vital to maintain a reasonable level of the surge capacity for successful implementation of the 2013–2018 global polio endgame strategy and beyond.

Notes from the Field: Circulating Vaccine-Derived Poliovirus Outbreaks - Five Countries, 2014-2015.

In 2015, wild poliovirus (WPV) transmission was identified in only Afghanistan and Pakistan (1). The widespread use of live, attenuated oral poliovirus vaccine (OPV) has been key in polio eradication efforts. However, OPV use, particularly in areas with low vaccination coverage, is associated with the low risk for emergence of vaccine-derived polioviruses (VDPV), which can cause paralysis (2). VDPVs vary genetically from vaccine viruses and can cause outbreaks in areas with low vaccination coverage. Circulating VDPVs (cVDPVs) are VDPVs in confirmed outbreaks. Single VDPVs for which the origin cannot be determined are classified as ambiguous (aVDPVs), which can also cause paralysis. Among the three types of WPV, type 2 has been declared to be eradicated. More than 90% of cVDPV cases have been caused by type 2 cVDPVs (cVDPV2). Therefore, in April 2016, all OPV-using countries of the world are discontinuing use of type 2 Sabin vaccine by simultaneously switching from trivalent OPV (types 1, 2, and 3) to bivalent OPV (types 1 and 3) for routine and supplementary immunization. The World Health Organization recently broadened the definition of cVDPVs to include any VDPV with genetic evidence of prolonged transmission (i.e., >1.5 years) and indicated that any single VDPV2 event (a case of paralysis caused by a VDPV or isolation of a VDPV from an environmental specimen) should elicit a detailed outbreak investigation and local immunization response. A confirmed cVDPV2 detection should elicit a full poliovirus outbreak response that includes multiple supplemental immunization activities (SIAs); an aVDPV designation should be made only after investigation and response (3). Since 2005, there have been 1-8 cVDPV outbreaks and 3-12 aVDPV events per year. There are currently five active cVDPV outbreaks in Guinea, Laos, Madagascar, Myanmar, and Ukraine, and four other active VDPV events.

Revised Household-Based Microplanning in Polio Supplemental Immunization Activities in Kano State, Nigeria. 2013-2014.

Background. Remarkable progress had been made since the launch of the Global Polio Eradication Initiative in 1988. However endemic wild poliovirus transmission in Nigeria, Pakistan, and Afghanistan remains an issue of international concern. Poor microplanning has been identified as a major contributor to the high numbers of chronically missed children.Methods. We assessed the contribution of the revised household-based microplanning process implemented in Kano State from September 2013 to April 2014 to the outcomes of subsequent polio supplemental immunization activities using used preselected planning and outcome indicators.Results. There was a 38% increase in the number of settlements enumerated, a 30% reduction in the number of target households, and a 54% reduction in target children. The reported number of children vaccinated and the doses of oral polio vaccine used during subsequent polio supplemental immunization activities showed a decline. Postvaccination lot quality assurance sampling and chronically missed settlement reports also showed a progressive reduction in the number of children and settlements missed.Conclusions. We observed improvement in Kano State's performance based on the selected postcampaign performance evaluation indicators and reliability of baseline demographic estimates after the revised household-based microplanning exercise.

Poliomyelitis: residual hurdles to global eradication. Commentary.

The global eradication of polio is close to achieving success. However, transmission of wild poliovirus persists in countries where the disease is endemic, and outbreaks may also occur in previously polio-free countries where population immunity is not maintained. To achieve polio eradication, several key actions are required: (1) to detect any poliovirus transmission, (2) to strengthen immunization systems and withdraw all oral polio vaccines from use, (3) to contain polioviruses and certify interruption of transmission, and (4) to sustain ongoing public health programs. In this context, residual hurdles to global polio eradication have been identified, from unstable political situation in affected countries to population movements from and to endemic areas, and opposition to immunization strategies. Global efforts are needed in order to promote routine immunization campaigns and large-scale vaccination rounds, which may provide direct protection of individuals and minimize virus circulation.

Molecular Characterization of Polio from Environmental Samples: ISSP, The Israeli Sewage Surveillance Protocol.

Polioviruses are enteric viruses that cause paralytic poliomyelitis in less than 0.5 % of infections and are asymptomatic in >90 % infections of naïve hosts. Environmental surveillance monitors polio in populations rather than in individuals. When this very low morbidity to infection ratio, drops drastically in highly vaccinated populations, environmental surveillance employing manual or automatic sampling coupled with molecular analysis carried out in well-equipped central laboratories becomes the surveillance method of choice since polioviruses are excreted by infected individuals regardless of whether or not the infection is symptomatic. This chapter describes a high throughput rapid turn-around time method for molecular characterization of polioviruses from sewage. It is presented in five modules: (1) Sewage collection and concentration of the viruses in the sewage; (2) Cell cultures for identification of virus in the concentrated sewage; (3) Nucleic acid extractions directly from sewage and from tissue cultures infected with aliquots of concentrated sewage; (4) Nucleic Acid Amplification for poliovirus serotype identification and intratypic differentiation (discriminating wild and vaccine derived polioviruses form vaccine strains); and (5) Molecular characterization of viral RNA by qRT-PCR, TR-PCR, and Sequence analysis. Monitoring silent or symptomatic transmission of vaccine-derived polioviruses or wild polioviruses is critical for the endgame of poliovirus eradication. We present methods for adapting standard kits and validating the changes for this purpose based on experience gained during the recent introduction and sustained transmission of a wild type 1 poliovirus in Israel in 2013 in a population with an initial IPV vaccine coverage >90 %.

High Incidence of Mammalian Orthoreovirus Identified by Environmental Surveillance in Taiwan.

Wild poliovirus (WPV) persists in diverse locales worldwide, spreading outward from endemic areas. In response to the international threat of WPV transmission and changes in the national vaccination policy, we established an environmental surveillance system to monitor the circulation of wild and vaccine-related poliovirus in Taiwan. From July 2012 to December 2013, we collected sewage specimens every month from 10 sewage treatment plants located throughout Taiwan. The specimens were concentrated by the two-phase separation method and then inoculated into L20B, RD, and A549 cells for virus isolation. Viral isolates were identified and serotyped by immunofluorescence assay or molecular analysis. A total of 300 sewage samples were collected, and the results showed 163 samples (54.3%) were positive for virus, and 268 isolates were identified. Among these, 75 samples (25%) were positive for enterovirus (EV), but no poliovirus was found. In addition, 92 isolates were identified as enteroviruses and the most common serotypes were coxsackievirus B4, coxsackievirus B3, and coxsackievirus B2. Interestingly, 102 (34%) and 82 (27.3%) specimens were positive for mammalian orthoreovirus (MRV) and adenovirus, respectively. This study confirmed that sewage surveillance can be a useful additional modality for monitoring the possible presence of wild-type or vaccine-derived poliovirus in wastewater, and can indicate the current types of viruses circulating in the population. Furthermore, since MRV was found in children with acute necrotizing encephalopathy and meningitis, the high incidence of MRV detected by environmental surveillance warrants further investigation.

Progress Toward Poliomyelitis Eradication--Afghanistan, January 2014‒August 2015.

Despite recent progress toward global polio eradication, endemic transmission of wild poliovirus (WPV) continues to be reported in Afghanistan and Pakistan. The Afghanistan program must overcome many challenges to remain on track toward achieving the objectives set in the 2013–2018 strategic plan of the Global Polio Eradication Initiative (GPEI). Cross-border transmission of WPV type 1 (WPV1) continues to occur among children traveling to and from Pakistan. The country's routine immunization system remains weak and unable to reach recommended benchmarks in most regions; hence, the national Polio Eradication Initiative (PEI) relies mainly on providing children aged <5 years with oral poliovirus vaccine (OPV), administered during supplementary immunization activities (SIAs). Because of ongoing conflict and insecurity, some children continue to be missed during SIAs in areas not under government control; however, the majority of missed children live in accessible areas and are often unreached because of a failure to plan, implement, and supervise SIAs efficiently. This report describes polio eradication activities and progress in Afghanistan during January 2014‒August 2015 and updates previous reports. During 2014, a total of 28 WPV1 cases were reported in Afghanistan, compared with 14 cases in 2013; nine cases were reported during January‒August 2015, the same number as during the same period in 2014. To eliminate poliovirus transmission in Afghanistan, emergency operations centers (EOCs) need to be established at the national level and in critical regions without delay to improve overall coordination and oversight of polio eradication activities. The recently revised National Emergency Action Plan for polio eradication needs to be fully implemented, including detailed microplanning and enhanced monitoring and supervision of SIAs, as well as improved cross-border coordination with Pakistan.