Supportive public health leadership for COVID-19 response in Jordan.

Background: The WHO Regional Office for the Eastern Mediterranean and the United Nations System Staff College (UNSSC) implemented a leadership programme on epidemic and pandemic preparedness and response, specific to the COVID-19 pandemic, during the second half of 2021. Aims: To highlight the leadership role played by the WHO Jordan Country Office during the COVID-19 pandemic in collaboration with UNSSC. Programme: The WHO Jordan country office successfully leveraged the expertise of UNSSC to implement a leadership training to prepare key stakeholders in Jordan for the response to COVID-19 and similar pandemics or outbreaks. The training curriculum included several modules such as leadership in times of crisis, strategic thinking and planning, emotional resilience, preparedness, adopting a system approach to response, and multisectoral partnership-building for pandemic response. The training helped strengthen the generation of evidence for policymaking and promotion of equitable access to health during the COVID-19 pandemic. Conclusion: Leadership capacity strengthening of national counterparts by WHO and partners can help advance efforts at national level to increase the use of evidence for policymaking and response to pandemics and disease outbreaks.

Surveillance To Track Progress Toward Poliomyelitis Eradication - Worldwide, 2021-2022.

Since the Global Polio Eradication Initiative (GPEI) was established in 1988, the number of wild poliovirus (WPV) cases has declined by >99.9%, and WPV serotypes 2 and 3 have been declared eradicated (1). By the end of 2022, WPV type 1 (WPV1) transmission remained endemic only in Afghanistan and Pakistan (2,3). However, during 2021-2022, Malawi and Mozambique reported nine WPV1 cases that were genetically linked to Pakistan (4,5), and circulating vaccine-derived poliovirus (cVDPV) outbreaks were detected in 42 countries (6). cVDPVs are oral poliovirus vaccine-derived viruses that can emerge after prolonged circulation in populations with low immunity allowing reversion to neurovirulence and can cause paralysis. Polioviruses are detected primarily through surveillance for acute flaccid paralysis (AFP), and poliovirus is confirmed through stool specimen testing. Environmental surveillance, the systematic sampling of sewage and testing for the presence of poliovirus, supplements AFP surveillance. Both surveillance systems were affected by the COVID-19 pandemic's effects on public health activities during 2020 (7,8) but improved in 2021 (9). This report updates previous reports (7,9) to describe surveillance performance during 2021-2022 in 34 priority countries.* In 2022, a total of 26 (76.5%) priority countries met the two key AFP surveillance performance indicator targets nationally compared with 24 (70.6%) countries in 2021; however, substantial gaps remain in subnational areas. Environmental surveillance expanded to 725 sites in priority countries, a 31.1% increase from the 553 sites reported in 2021. High-quality surveillance is critical to rapidly detect poliovirus transmission and enable prompt poliovirus outbreak response to stop circulation. Frequent monitoring of surveillance guides improvements to achieve progress toward polio eradication.

External quality assessment of laboratory performance in bacteriology in the Eastern Mediterranean Region, 2011-2019.

Background: Since 2007, national public health laboratories in the WHO Eastern Mediterranean Region (EMR) have participated in a regional external quality assessment scheme in bacteriology to improve testing proficiency. Aims: To assess laboratory performance in bacteriology in the EMR between 2011 and 2019 using the regional external quality assessment scheme. Methods: We analysed the accuracy of participant-reported data in bacterial identification, Gram stain microscopy, and antimicrobial susceptibility testing. For each category, we assessed the performance over time, the performance on multiple organisms, and whether a laboratory repeatedly failed to attain satisfactory results. Results: Between 2011 and 2019, 70% of laboratories achieved satisfactory performance for bacterial identification and antimicrobial susceptibility testing, and 85% performed satisfactory Gram stain microscopy. Testing did not improve on multiple organisms and results were consistently low for some pathogens and test categories. Twenty-nine percent of laboratories underperformed throughout the study period. Conclusion: The unchanged performance over time and underperformance of laboratories highlight the need for improvements in the regional external quality assessment scheme. Participating laboratories and WHO need to work more actively to strengthen the problem areas.

Stopping a polio outbreak in the midst of war: Lessons from Syria.

BACKGROUND: Outbreaks of circulating vaccine-derived polioviruses (cVDPVs) pose a threat to the eventual eradication of all polioviruses. In 2017, an outbreak of cVDPV type 2 (cVDPV2) occurred in the midst of a war in Syria. We describe vaccination-based risk factors for and the successful response to the outbreak. METHODS: We performed a descriptive analysis of cVDPV2 cases and key indicators of poliovirus surveillance and vaccination activities during 2016-2018. In the absence of reliable subnational coverage data, we used the caregiver-reported vaccination status of children with non-polio acute flaccid paralysis (AFP) as a proxy for vaccination coverage. We then estimated the relative odds of being unvaccinated against polio, comparing children in areas affected by the outbreak to children in other parts of Syria in order to establish the presence of poliovirus immunity gaps in outbreak affected areas. FINDINGS: A total of 74 cVDPV2 cases were reported, with paralysis onset ranging from 3 March to 21 September 2017. All but three cases were reported from Deir-ez-Zor governorate and 84% had received < 3 doses of oral poliovirus vaccine (OPV). After adjusting for age and sex, non-polio AFP case-patients aged 6-59 months in outbreak-affected areas had 2.5 (95% CI: 1.1-5.7) increased odds of being unvaccinated with OPV compared with non-polio AFP case-patients in the same age group in other parts of Syria. Three outbreak response rounds of monovalent OPV type 2 (mOPV2) vaccination were conducted, with governorate-level coverage mostly exceeding 80%. INTERPRETATION: Significant declines in both national and subnational polio vaccination coverage, precipitated by war and a humanitarian crisis, led to a cVDPV2 outbreak in Syria that was successfully contained following three rounds of mOPV2 vaccination.

Strengthening National Immunization Technical Advisory Groups in resource-limited settings: current and potential linkages with polio national certification committees.

BACKGROUND: Countries are transitioning assets and functions from polio eradication to integrated immunization and surveillance activities. We assessed the extent of linkages between and perceptions of National Immunization Technical Advisory Groups (NITAGs) and National Certification Committees (NCCs) for polio eradication to understand how linkages can be leveraged to improve efficiencies of these expert bodies. METHODS: During May 2017 to May 2018, we administered a 15-question survey to a NITAG chair or member and an NCC counterpart in all countries of the WHO Regions for Africa (AFR) and for the Eastern Mediterranean (EMR) that had both a NITAG and an NCC. Data were analysed using frequency distributions. RESULTS: Of countries with both a NITAG and an NCC (n = 44), the response rate was 92% (22/24) in AFR and 75% (15/20) in EMR. Some respondents reported being very familiar with the functions of the other technical bodies, 36% (8/22) for NITAG members and 38% (14/37) for NCC members. Over 85% (51/59) of respondents felt it was somewhat useful or very useful to strengthen ties between bodies. Nearly all respondents (98%, 58/59) felt that NCC expertise could inform measles and rubella elimination programmes. CONCLUSIONS: We observed a broad consensus that human resource assets of NCCs may serve an important technical role to support national immunization policy-making. At this stage of the polio eradication initiative, countries should consider how to integrate the technical expertise of NCC members to reinforce NITAGs and maintain the polio essential functions, beginning in countries that have been polio-free for several years.

Progress Toward Poliovirus Containment Implementation - Worldwide, 2019-2020.

Since 1988, when World Health Organization (WHO) Member States and partners launched the Global Polio Eradication Initiative, the number of wild poliovirus (WPV) cases has declined from 350,000 in 125 countries to 176 in only two countries in 2019 (1). The Global Commission for the Certification of Poliomyelitis Eradication (GCC) declared two of the three WPV types, type 2 (WPV2) and type 3 (WPV3), eradicated globally in 2015 and 2019, respectively (1). Wild poliovirus type 1 (WPV1) remains endemic in Afghanistan and Pakistan (1). Containment under strict biorisk management measures is vital to prevent reintroduction of eradicated polioviruses into communities from poliovirus facilities. In 2015, Member States committed to contain type 2 polioviruses (PV2) in poliovirus-essential facilities (PEFs) certified in accordance with a global standard (2). Member states agreed to report national PV2 inventories annually, destroy unneeded PV2 materials, and, if retaining PV2 materials, establish national authorities for containment (NACs) and a PEF auditing process. Since declaration of WPV3 eradication in October 2019, these activities are also required with WPV3 materials. Despite challenges faced during 2019-2020, including the coronavirus disease 2019 (COVID-19) pandemic, the global poliovirus containment program continues to work toward important milestones. To maintain progress, all WHO Member States are urged to adhere to the agreed containment resolutions, including officially establishing legally empowered NACs and submission of PEF Certificates of Participation.

Rapid and Sensitive Direct Detection and Identification of Poliovirus from Stool and Environmental Surveillance Samples by Use of Nanopore Sequencing.

Global poliovirus surveillance involves virus isolation from stool and environmental samples, intratypic differential (ITD) by PCR, and sequencing of the VP1 region to distinguish vaccine (Sabin), vaccine-derived, and wild-type polioviruses and to ensure an appropriate response. This cell culture algorithm takes 2 to 3 weeks on average between sample receipt and sequencing. Direct detection of viral RNA using PCR allows faster detection but has traditionally faced challenges related to poor sensitivity and difficulties in sequencing common samples containing poliovirus and enterovirus mixtures. We present a nested PCR and nanopore sequencing protocol that allows rapid (<3 days) and sensitive direct detection and sequencing of polioviruses in stool and environmental samples. We developed barcoded primers and a real-time analysis platform that generate accurate VP1 consensus sequences from multiplexed samples. The sensitivity and specificity of our protocol compared with those of cell culture were 90.9% (95% confidence interval, 75.7% to 98.1%) and 99.2% (95.5% to 100.0%) for wild-type 1 poliovirus, 92.5% (79.6% to 98.4%) and 98.7% (95.4% to 99.8%) for vaccine and vaccine-derived serotype 2 poliovirus, and 88.3% (81.2% to 93.5%) and 93.2% (88.6% to 96.3%) for Sabin 1 and 3 poliovirus alone or in mixtures when tested on 155 stool samples in Pakistan. Variant analysis of sequencing reads also allowed the identification of polioviruses and enteroviruses in artificial mixtures and was able to distinguish complex mixtures of polioviruses in environmental samples. The median identity of consensus nanopore sequences with Sanger or Illumina sequences from the same samples was >99.9%. This novel method shows promise as a faster and safer alternative to cell culture for the detection and real-time sequencing of polioviruses in stool and environmental samples.

Surveillance to Track Progress Toward Polio Eradication - Worldwide, 2018-2019.

Since the Global Polio Eradication Initiative (GPEI) was launched in 1988, the number of polio cases worldwide has declined approximately 99.99%; only two countries (Afghanistan and Pakistan) have never interrupted wild poliovirus (WPV) transmission (1). The primary means of detecting poliovirus circulation is through surveillance for acute flaccid paralysis (AFP) among children aged <15 years with testing of stool specimens for WPV and vaccine-derived polioviruses (VDPVs) (genetically reverted strains of the vaccine virus that regain neurovirulence) in World Health Organization (WHO)-accredited laboratories (2,3). In many locations, AFP surveillance is supplemented by environmental surveillance, the regular collection and testing of sewage to provide awareness of the extent and duration of poliovirus circulation (3). This report presents 2018-2019 poliovirus surveillance data, focusing on 40 priority countries* with WPV or VDPV outbreaks or at high risk for importation because of their proximity to a country with an outbreak. The number of priority countries rose from 31 in 2018 to 40 in 2019 because of a substantial increase in the number of VDPV outbreaks† (2,4). In areas with low poliovirus immunity, VDPVs can circulate in the community and cause outbreaks of paralysis; these are known as circulating vaccine derived polioviruses (cVDPVs) (4). In 2019, only 25 (63%) of the 40 designated priority countries met AFP surveillance indicators nationally; subnational surveillance performance varied widely and indicated focal weaknesses. High quality, sensitive surveillance is important to ensure timely detection and response to cVDPV and WPV transmission.

Progress Toward Poliovirus Containment Implementation - Worldwide, 2018-2019.

Among the three wild poliovirus (WPV) types, type 2 (WPV2) was declared eradicated globally by the Global Commission for the Certification of Poliomyelitis Eradication (GCC) in 2015. Subsequently, in 2016, a global withdrawal of Sabin type 2 oral poliovirus vaccine (OPV2) from routine use, through a synchronized switch from the trivalent formulation of oral poliovirus vaccine (tOPV, containing vaccine virus types 1, 2, and 3) to the bivalent form (bOPV, containing types 1 and 3), was implemented. WPV type 3 (WPV3), last detected in 2012 (1), will possibly be declared eradicated in late 2019.* To ensure that polioviruses are not reintroduced to the human population after eradication, World Health Organization (WHO) Member States committed in 2015 to containing all polioviruses in poliovirus-essential facilities (PEFs) that are certified to meet stringent containment criteria; implementation of containment activities began that year for facilities retaining type 2 polioviruses (PV2), including type 2 oral poliovirus vaccine (OPV) materials (2). As of August 1, 2019, 26 countries have nominated 74 PEFs to retain PV2 materials. Twenty-five of these countries have established national authorities for containment (NACs), which are institutions nominated by ministries of health or equivalent bodies to be responsible for poliovirus containment certification. All designated PEFs are required to be enrolled in the certification process by December 31, 2019 (3). When GCC certifies WPV3 eradication, WPV3 and vaccine-derived poliovirus (VDPV) type 3 materials will also be required to be contained, leading to a temporary increase in the number of designated PEFs. When safer alternatives to wild and OPV/Sabin strains that do not require containment conditions are available for diagnostic and serologic testing, the number of PEFs will decrease. Facilities continuing to work with polioviruses after global eradication must minimize the risk for reintroduction into communities by adopting effective biorisk management practices.

Identifying hotspots of viral haemorrhagic fevers in the Eastern Mediterranean Region: perspectives for the Emerging and Dangerous Pathogens Laboratory Network.

BACKGROUND: The emergence and re-emergence of viral haemorrhagic fevers (VHFs) is a growing concern worldwide. They are associated with major epidemics with an estimated 51-101 million cases each year, of which around 67 000 are fatal. In 2007, 13 countries in the Eastern Mediterranean Region reported VHF cases. AIMS: The main purpose of the study was to review the epidemiological situation in the Region vis-à-vis VHFs to obtain baseline epidemiological information for the establishment of the Emerging Dangerous Pathogen Laboratory Network (EDPLN). METHODS: A literature search was performed using PubMed, ProMED-Mail and GIDEON databases. Reported data included disease burden (reported cases and deaths), human prevalence (general population, high-risk groups), vectors and reservoirs. A scoring method was employed to divide countries into 4 groups (very highly, highly, medium and low affected countries). RESULTS: Very highly affected countries were Afghanistan, Egypt, Islamic Republic of Iran, Saudi Arabia and Sudan. Highly affected countries were Djibouti, Morocco, Oman, Pakistan, Tunisia and Yemen. Medium affected countries were Iraq, Somalia and United Arab Emirates. Low affected countries were Bahrain, Jordan, Lebanon, Libya, Palestine, Qatar and Syrian Arab Republic. CONCLUSIONS: This study contributes in prioritizing countries to be part of EDPLN and in addressing specific needs related to outbreak investigations, surveillance and research.

Environmental Surveillance Reveals Complex Enterovirus Circulation Patterns in Human Populations.

BACKGROUND: Enteroviruses are common human pathogens occasionally associated with severe disease, notoriously paralytic poliomyelitis caused by poliovirus. Other enterovirus serotypes such as enterovirus A71 and D68 have been linked to severe neurological syndromes. New enterovirus serotypes continue to emerge, some believed to be derived from nonhuman primates. However, little is known about the circulation patterns of many enterovirus serotypes and, in particular, the detailed enterovirus composition of sewage samples. METHODS: We used a next-generation sequencing approach analyzing reverse transcriptase polymerase chain reaction products synthesized directly from sewage concentrates. RESULTS: We determined whole-capsid genome sequences of multiple enterovirus strains from all 4 A to D species present in environmental samples from the United Kingdom, Senegal, and Pakistan. CONCLUSIONS: Our results indicate complex enterovirus circulation patterns in human populations with differences in serotype composition between samples and evidence of sustained and widespread circulation of many enterovirus serotypes. Our analyses revealed known and divergent enterovirus strains, some of public health relevance and genetically linked to clinical isolates. Enteroviruses identified in sewage included vaccine-derived poliovirus and enterovirus D-68 stains, new enterovirus A71 and coxsackievirus A16 genogroups indigenous to Pakistan, and many strains from rarely reported serotypes. We show how this approach can be used for the early detection of emerging pathogens and to improve our understanding of enterovirus circulation in humans.

Evaluation of the bag-mediated filtration system as a novel tool for poliovirus environmental surveillance: Results from a comparative field study in Pakistan.

Poliovirus (PV) environmental surveillance (ES) plays an important role in the global eradication program and is crucial for monitoring silent PV circulation especially as clinical cases decrease. This study compared ES results using the novel bag-mediated filtration system (BMFS) with the current two-phase separation method. From February to November 2016, BMFS and two-phase samples were collected concurrently from twelve sites in Pakistan (n = 117). Detection was higher in BMFS than two-phase samples for each Sabin-like (SL) PV serotype (p<0.001) and wild PV type 1 (WPV1) (p = 0.065). Seventeen sampling events were positive for WPV1, with eight discordant in favor of BMFS and two in favor of two-phase. A vaccine-derived PV type 2 was detected in one BMFS sample but not the matched two-phase. After the removal of SL PV type 2 (SL2) from the oral polio vaccine in April 2016, BMFS samples detected SL2 more frequently than two-phase (p = 0.016), with the last detection by either method occurring June 12, 2016. More frequent PV detection in BMFS compared to two-phase samples is likely due to the greater effective volume assayed (1620 mL vs. 150 mL). This study demonstrated that the BMFS achieves enhanced ES for all PV serotypes in an endemic country.

Strategic Response to an Outbreak of Circulating Vaccine-Derived Poliovirus Type 2 - Syria, 2017-2018.

Since the 1988 inception of the Global Polio Eradication Initiative (GPEI), progress toward interruption of wild poliovirus (WPV) transmission has occurred mostly through extensive use of oral poliovirus vaccine (OPV) in mass vaccination campaigns and through routine immunization services (1,2). However, because OPV contains live, attenuated virus, it carries the rare risk for reversion to neurovirulence. In areas with very low OPV coverage, prolonged transmission of vaccine-associated viruses can lead to the emergence of vaccine-derived polioviruses (VDPVs), which can cause outbreaks of paralytic poliomyelitis. Although WPV type 2 has not been detected since 1999, and was declared eradicated in 2015,* most VDPV outbreaks have been attributable to VDPV serotype 2 (VDPV2) (3,4). After the synchronized global switch from trivalent OPV (tOPV) (containing vaccine virus types 1, 2, and 3) to bivalent OPV (bOPV) (types 1 and 3) in April 2016 (5), GPEI regards any VDPV2 emergence as a public health emergency (6,7). During May-June 2017, VDPV2 was isolated from stool specimens from two children with acute flaccid paralysis (AFP) in Deir-ez-Zor governorate, Syria. The first isolate differed from Sabin vaccine virus by 22 nucleotides in the VP1 coding region (903 nucleotides). Genetic sequence analysis linked the two cases, confirming an outbreak of circulating VDPV2 (cVDPV2). Poliovirus surveillance activities were intensified, and three rounds of vaccination campaigns, aimed at children aged <5 years, were conducted using monovalent OPV type 2 (mOPV2). During the outbreak, 74 cVDPV2 cases were identified; the most recent occurred in September 2017. Evidence indicates that enhanced surveillance measures coupled with vaccination activities using mOPV2 have interrupted cVDPV2 transmission in Syria.

Population sensitivity of acute flaccid paralysis and environmental surveillance for serotype 1 poliovirus in Pakistan: an observational study.

BACKGROUND: To support poliomyelitis eradication in Pakistan, environmental surveillance (ES) of wastewater has been expanded alongside surveillance for acute flaccid paralysis (AFP). ES is a relatively new method of surveillance, and the population sensitivity of detecting poliovirus within endemic settings requires estimation. METHODS: Data for wild serotype 1 poliovirus from AFP and ES from January 2011 to September 2015 from 14 districts in Pakistan were analysed using a multi-state model framework. This framework was used to estimate the sensitivity of poliovirus detection from each surveillance source and parameters such as the duration of infection within a community. RESULTS: The location and timing of poliomyelitis cases showed spatial and temporal variability. The sensitivity of AFP surveillance to detect serotype 1 poliovirus infection in a district and its neighbours per month was on average 30.0% (95% CI 24.8-35.8) and increased with the incidence of poliomyelitis cases. The average population sensitivity of a single environmental sample was 59.4% (95% CI 55.4-63.0), with significant variation in site-specific estimates (median varied from 33.3-79.2%). The combined population sensitivity of environmental and AFP surveillance in a given month was on average 98.1% (95% CI 97.2-98.7), assuming four samples per month for each site. CONCLUSIONS: ES can be a highly sensitive supplement to AFP surveillance in areas with converging sewage systems. As ES for poliovirus is expanded, it will be important to identify factors associated with variation in site sensitivity, leading to improved site selection and surveillance system performance.

Progress on the Implementation of Environmental Surveillance in the African Region, 2011-2016.

OBJECTIVE: This article summarises the progress made since the introduction of environmental surveillance in the African Region. METHOD: Country selection was based on the poor AFP performance indicators i.e. Non polio AFP rate and stool adequacy. It was recommended that any country not meeting the required indicators should consider environmental surveillance activity as an additional tool to support AFP surveillance. The sites selection considered proximity to the target population, the size of the population to be sampled and the sensitivity of the sampling site. RESULTS: One hundred and fifty three sites have been established in Africa since 2011. In 2011, Nigeria was first country to introduce environmental surveillance and currently with of 59 validated sites, followed by Kenya in 2013 validating and sampling 9 sites and Angola 4 active sites in 2014. In 2014, Cameroon introduced ES and 31 sites followed by Niger with 9 sites and Madagascar with 23 sites. Later in the same year, Chad introduced ES activity and 4 active sites were selected. In 2015 Senegal introduced 3 sites, Guinea and Burkina Faso introduced 4 sites each., and. In 2016, a total of 179 Sabins, 36 Sabin 2s, 196 non polio enteroviruses (NPEV) and 1 vaccine-derived polioviruses (VDPV) were reported in Nigeria. Cameroon and Chad isolated 14 and 4 Sabins and 72 and 40 NPEV respectively. In Madagascar a total of 39 Sabins, 11 Sabin 2s and 277 NPEV were isolated. In other countries a majority of NPEV were isolated (data not shown). CONCLUSION: This report describes the progress and expansion of environmental surveillance that contributed to the identification of polioviruses from the environment and the interruption of wild poliovirus transmission in the African Region.

Virologic Monitoring of Poliovirus Type 2 after Oral Poliovirus Vaccine Type 2 Withdrawal in April 2016 - Worldwide, 2016-2017.

The Global Polio Eradication Initiative (GPEI) has made substantial progress since its launch in 1988; only 37 wild poliovirus type 1 (WPV1) cases were detected in 2016, the lowest annual count ever. Wild poliovirus type 3 has not been detected since November 2012, and wild poliovirus type 2 was officially declared eradicated in September 2015. This success is attributable to the wide use of live oral poliovirus vaccines (OPVs). Since 2001, numerous outbreaks were caused by the emergence of genetically divergent vaccine-derived polioviruses (VDPVs) whose genetic drift from the parental OPV strains indicates prolonged replication or circulation (1). In 2015, circulating VDPV type 2 (cVDPV2) outbreaks were detected in five countries worldwide (Nigeria, Pakistan, Guinea, Burma, and South Sudan), and VDPV2 single events were reported in 22 countries. These events prompted the GPEI to withdraw the type 2 component (Sabin2) of trivalent OPV (tOPV) in a globally coordinated, synchronized manner in April 2016 (2,3), at which time all OPV-using countries switched to using bivalent OPV (bOPV), containing Sabin types 1 and 3. This report details for the first time the virologic tracking of elimination of a live vaccine that has been withdrawn from routine and mass immunization systems worldwide (3). To secure elimination, further monitoring is warranted to detect any use of tOPV or monovalent OPV type 2 (mOPV2).

Poliovirus Laboratory Based Surveillance: An Overview.

World Health Assembly (WHA) in 1988 encouraged the member states to launch Global Polio Eradication Initiative (GPEI) (resolution WHA41.28) against "the Crippler" called poliovirus, through strong routine immunization program and intensified surveillance systems. Since its launch, global incidence of poliomyelitis has been reduced by more than 99 % and the disease squeezed to only three endemic countries (Afghanistan, Pakistan, and Nigeria) out of 125. Today, poliomyelitis is on the verge of eradication, and their etiological agents, the three poliovirus serotypes, are on the brink of extinction from the natural environment. The last case of poliomyelitis due to wild type 2 strain occurred in 1999 in Uttar Pradesh, India whereas the last paralytic case due to wild poliovirus type 3 (WPV3) was seen in November, 2012 in Yobe, Nigeria. Despite this progress, undetected circulation cannot fully rule out the eradication as most of the poliovirus infections are entirely subclinical; hence sophisticated environmental surveillance is needed to ensure the complete eradication of virus. Moreover, the vaccine virus in under-immunized communities can sometimes revert and attain wild type characteristics posing a big challenge to the program.

Environmental surveillance for polioviruses in the Global Polio Eradication Initiative.

This article summarizes the status of environmental surveillance (ES) used by the Global Polio Eradication Initiative, provides the rationale for ES, gives examples of ES methods and findings, and summarizes how these data are used to achieve poliovirus eradication. ES complements clinical acute flaccid paralysis (AFP) surveillance for possible polio cases. ES detects poliovirus circulation in environmental sewage and is used to monitor transmission in communities. If detected, the genetic sequences of polioviruses isolated from ES are compared with those of isolates from clinical cases to evaluate the relationships among viruses. To evaluate poliovirus transmission, ES programs must be developed in a manner that is sensitive, with sufficiently frequent sampling, appropriate isolation methods, and specifically targeted sampling sites in locations at highest risk for poliovirus transmission. After poliovirus ceased to be detected in human cases, ES documented the absence of endemic WPV transmission and detected imported WPV. ES provides valuable information, particularly in high-density populations where AFP surveillance is of poor quality, persistent virus circulation is suspected, or frequent virus reintroduction is perceived. Given the benefits of ES, GPEI plans to continue and expand ES as part of its strategic plan and as a supplement to AFP surveillance.

Detection of imported wild polioviruses and of vaccine-derived polioviruses by environmental surveillance in Egypt.

Systematic environmental surveillance for poliovirus circulation has been conducted in Egypt since 2000. The surveillance has revealed three independent importations of wild-type poliovirus. In addition, several vaccine-derived polioviruses have been detected in various locations in Egypt. In addition to acute flaccid paralysis (AFP) surveillance, environmental surveillance can be used to monitor the wild poliovirus and vaccine-derived poliovirus circulation in populations in support of polio eradication initiatives.