Detection of multiple cocirculating wild poliovirus type 1 lineages through environmental surveillance: impact and progress during 2011-2013 in Pakistan

Environmental Surveillance of Poliovirus and Non-polio Enteroviruses in Iran, 2017-2023: First Report of Imported Wild Poliovirus Type 1 Since 2000

In Iran, which is at high risk of the Wild Poliovirus (WPV) and Vaccine-Derived Poliovirus (VDPV) importation due to its neighborhood with two polio endemic countries, Pakistan and Afghanistan, Environmental Surveillance (ES) was established in November 2017. Sistan-Balouchestan province was chosen for the ES due to its vicinity with Pakistan and Afghanistan. Five sewage collection sites in 4 cities (Zahedan, Zabol, Chabahar and Konarak) were selected in the high-risk areas. Since the establishment of ES in November 2017 till the end of 2023, 364 sewage specimens were collected and analyzed. The ES detected polioviruses which have the highest significance for polio eradication program, that is, Wild Poliovirus type 1 (WPV1) and Poliovirus type 2 (PV2). In April and May 2019, three of 364 (0.8%) sewage specimens from Konarak were positive for imported WPV1. According to phylogenetic analysis, they were highly related to WPV1 circulating in Karachi (Sindh province) in Pakistan. PV2 was also detected in 5.7% (21/364) of the sewage specimens, most of which proved to be imported from the neighboring countries. Of 21 isolated PV2s, 7 were VDPV2, of which 5 proved to be imported from the neighboring countries as there was VDPV2 circulating in Pakistan at the time of sampling, and 2 were ambiguous VDPVs (aVDPV) with unknown source. According to the findings of this study, as long as WPV1 and VDPV2 outbreaks are detected in Iran's neighboring countries, there is a definite need for continuation and expansion of the environmental surveillance.

Evaluation of the environmental polio surveillance system-Northern Region, Ghana, 2021

BACKGROUND

Acute Flaccid Paralysis (AFP) surveillance is the gold standard in the polio eradication initiative. The environmental component of polio surveillance can detect circulating Polioviruses from sewage without relying on clinical presentation. The effectiveness of the Environmental Surveillance (ES) is crucial to global polio eradication. We assessed the usefulness and attributes of the ES system in the Northern region and determined if the system is meeting its objectives.

METHODS

We conducted a descriptive cross-sectional evaluation in the Northern region from 2019 to 2020 using the updated US Centers for Disease Control and Prevention guideline. We interviewed stakeholders, reviewed records, and observed surveillance activities from 29th March to 7th May, 2021. Quantitative data were analyzed manually as frequencies and proportions whiles thematic analysis was used for the qualitative data.

RESULTS

One of 48 (2.1%) samples collected tested positive for circulating vaccine-derived Poliovirus (cVDPV). The cVDPV detection triggered enhanced AFP surveillance that resulted in the identification of a case of AFP. Three rounds of polio vaccination campaigns were organized. All surveillance officers interviewed were willing to continue providing their services for the ES. Reporting form has few variables and is easy to complete. The completeness of forms was 97.9% (47/48). Samples collected were dispatched on the same day to the testing laboratory. The system's data was managed manually.

CONCLUSION

The system was useful in detecting polio outbreaks. Data quality was good, the system was simple, flexible, acceptable, representative, and fairly stable. Sensitivity was high but predictive value positive was low. Timeliness in reporting was good but feedback from the national level could not be assessed. There is a need to improve on the feedback system and ensure that, the surveillance data is managed electronically.

Attitude and perception towards vaccination against poliomyelitis in Peshawar, Pakistan

OBJECTIVE:

This research aimed to quantitatively assess the general public's awareness, attitude and perception of polio and its vaccination in Peshawar KPK, Pakistan.

METHODS:

We conducted a survey-based study to understand the surge in polio cases from 2015 to 2019 in the Peshawar city of the Khyber Pakhtunkhwa (KPK), Pakistan. A pre-tested questionnaire-based study was conducted in 2019 to assess the attitude and general perception of residents of Peshawar KPK towards polio vaccination.

RESULTS:

Out of 241 country-wide polio cases, 63 (26.1%) polio cases were reported in Peshawar city from 2015–2019. The questionnaire revealed that individuals between 18–30 years of age had sufficient knowledge (65.1%) about polio. Male and female participants had equal awareness (~ 43%). Participants with higher education (45.9%), those with better financial status (49.5%), individuals with children < 5 years of age (46.4%), and those who had experience of a polio patient (63.1%) had better knowledge. Participants inhabiting the central city were better aware (50.5%) of polio than individuals living in the outskirts.

CONCLUSION:

The data indicated that poor knowledge and negative attitudes of people towards polio vaccination are the main causes of the polio eradication program's failure. Moreover, religious beliefs, unchecked migration between the Pak-Afghan border, and lack of knowledge about polio vaccination are identified as critical barriers to polio eradication.

Polio Outbreak Response; Evaluation of Acute Flaccid Paralysis Surveillance in Karbala, Iraq

Background:

After the last outbreak of wild polio infection in Baghdad, April 2014, the Iraqi response to the outbreak was activated through solid surveillance of Acute Flaccid Paralysis (AFP) case detection in all governorates to interrupt the circulation of poliovirus in addition to the strengthening of Expanded Program on Immunization. This response to the last outbreak has to be evaluated independently to ensure effective mopping and surveillance to stop further outbreak all over the country including the holy province Karbala. We aimed to evaluate the response to the last polio outbreak by evaluating surveillance activities of acute flaccid paralysis cases whether they meet the recommended standards.

Methods:

Observational evaluation study conducted through August 15–25, 2015. Checking of Acute Flaccid Paralysis surveillance (AFP) activity through detection of nonPolio acute flaccid paralysis rate and immediate reporting with adequate stool sampling, and 60 days follow-up examination four districts of the province. The reviewing checked whether the surveillance system in Karbala met the global standards required for stopping wild poliovirus circulation. The evaluation included immunization coverage rates and active National Immunization days of oral polio vaccine campaigns.

Results:

During the period of review, the core surveillance indicators in Karbala met the globally set standards. Percent of acute flaccid paralysis cases with specimens reached to the reference laboratory within 3 days was 100%. Nonpolio cases was 4.2 per 100000 population under 15 years of age through week 33 of the year 2015. Eleven AFP cases were reported from all districts of Karbala among Population of children under 15 years of age. The percentage of cases with adequate specimens was 100% in 2015 versus 93% in 2014. The percent of AFP Cases notified within 7 days of paralysis onset (during first 33 weeks) was 100% in 2015 versus 87% in 2014.

Conclusions:

As Karbala response to polio outbreak met the target global indicators and standards of polio surveillance. The circulation of the virus in this locality was interrupted and further transmission of the disease is unlikely.

Assessing the sensitivity of the polio environmental surveillance system

BACKGROUND

The polio environmental surveillance (ES) system has been an incredible tool for advancing polio eradication efforts because of its ability to highlight the spatial and temporal extent of poliovirus circulation. While ES often outperforms, or is more sensitive than AFP surveillance, the sensitivity of the ES system has not been well characterized. Fundamental uncertainty of ES site sensitivity makes it difficult to interpret results from ES, particularly negative results.

METHODS AND FINDINGS

To study ES sensitivity, we used data from Afghanistan and Pakistan to examine the probability that each ES site detected the Sabin 1, 2, or 3 components of the oral polio vaccine (OPV) as a function of virus prevalence within the same district (estimated from AFP data). Accounting for virus prevalence is essential for estimating site sensitivity because Sabin detection rates should vary with prevalence-high immediately after supplemental immunization activities (SIAs), but low in subsequent months. We found that most ES sites in Pakistan and Afghanistan are highly sensitive for detecting poliovirus relative to AFP surveillance in the same districts. For example, even when Sabin poliovirus is at low prevalence of ~0.5-3% in AFP surveillance, most ES sites have ~34-50% probability of detecting Sabin. However, there was considerable variation in ES site sensitivity and we flagged several sites for re-evaluation based on low sensitivity rankings and low wild polio virus detection rates. In these areas, adding new sites or modifying collection methods in current sites could improve sensitivity of environmental surveillance.

CONCLUSIONS

Relating ES detections to virus prevalence significantly improved our ability to evaluate site sensitivity compared to evaluations based solely on ES detection rates. To extend our approach to new sites and regions, we provide a preliminary framework for relating ES and AFP detection rates, and descriptions of how detection rates might relate to SIAs and natural seasonality.

An Environmental Surveillance in Uruguay Reveals the Presence of Highly Divergent Types of Human Enterovirus Species C and a High Frequency of Species A and B Types

Information about Human Enterovirus circulation in Uruguay is scarce. The aim of this study was to generate the first description about their circulation in the country through the study of sewage samples collected before and after the switch from Oral Poliovirus Vaccine to Inactivated Poliovirus Vaccine. Viruses were concentrated by an adsorption-elution to a negatively charged membrane, and real-time quantitative PCR and qualitative PCR methods were used to detect, quantify, and characterize enteroviruses. Positive samples were inoculated in RD cells and two passages were performed. Additionally, RD+ samples were subsequently passed onto L20B cells. Human Enteroviruses were detected in 67.6% of the samples, with concentrations between 4.9 and 6.6 Log₁₀ genomic copies per liter. 10% of positive samples replicated in RD cells, of which none in L20B cells. Molecular characterization of Human Enterovirus strains directly detected from sewage sample concentrates allowed the identification of highly divergent members of species C such as Enterovirus C99 and Coxsackievirus A13, as well as the frequent detection of species A and B members (particularly Coxsackievirus A16 and Echovirus 6, respectively). Other detected types were Coxsackievirus A2, A22, B1, B5, Echovirus 5, and 9. The characterization of viruses isolated in cell culture revealed the presence of Echovirus 6 and Coxsackievirus B3. Despite the absence of poliovirus, a wide circulation of different enterovirus types was evidenced in Uruguayan sewage samples, highlighting that the local populations are exposed to different kinds of diseases originated by several human enterovirus.

A Review of the Most Commonly Used Methods for Sample Collection in Environmental Surveillance of Poliovirus

We performed a review of the environmental surveillance methods commonly used to collect and concentrate poliovirus (PV) from water samples. We compared the sampling approaches (trap vs grab), the process methods (precipitation vs filtration), and the various tools and chemical reagents used to separate PV from other viruses and pathogens in water samples (microporous glass, pads, polyethylene glycol [PEG]/dextran, PEG/sodium chloride, NanoCeram/ViroCap, and ester membranes). The advantages and disadvantages of each method are considered, and the geographical areas where they are currently used are discussed. Several methods have demonstrated the ability to concentrate and recover PVs from environmental samples. The details of the particular sampling conditions and locations should be considered carefully in method selection.

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.

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.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3070-4) contains supplementary material, which is available to authorized users.

Insights from a Systematic Search for Information on Designs, Costs, and Effectiveness of Poliovirus Environmental Surveillance Systems

Poliovirus surveillance plays a critical role in achieving and certifying eradication and will play a key role in the polio endgame. Environmental surveillance can provide an opportunity to detect circulating polioviruses prior to the observation of any acute flaccid paralysis cases. We completed a systematic review of peer-reviewed publications on environmental surveillance for polio including the search terms "environmental surveillance" or "sewage," and "polio," "poliovirus," or "poliomyelitis," and compared characteristics of the resulting studies. The review included 146 studies representing 101 environmental surveillance activities from 48 countries published between 1975 and 2016. Studies reported taking samples from sewage treatment facilities, surface waters, and various other environmental sources, although they generally did not present sufficient details to thoroughly evaluate the sewage systems and catchment areas. When reported, catchment areas varied from 50 to over 7.3 million people (median of 500,000 for the 25% of activities that reported catchment areas, notably with 60% of the studies not reporting this information and 16% reporting insufficient information to estimate the catchment area population size). While numerous studies reported the ability of environmental surveillance to detect polioviruses in the absence of clinical cases, the review revealed very limited information about the costs and limited information to support quantitative population effectiveness of conducting environmental surveillance. This review motivates future studies to better characterize poliovirus environmental surveillance systems and the potential value of information that they may provide in the polio endgame.

Spatial model for risk prediction and sub-national prioritization to aid poliovirus eradication in Pakistan

BACKGROUND

Pakistan is one of only three countries where poliovirus circulation remains endemic. For the Pakistan Polio Eradication Program, identifying high risk districts is essential to target interventions and allocate limited resources.

METHODS

Using a hierarchical Bayesian framework we developed a spatial Poisson hurdle model to jointly model the probability of one or more paralytic polio cases, and the number of cases that would be detected in the event of an outbreak. Rates of underimmunization, routine immunization, and population immunity, as well as seasonality and a history of cases were used to project future risk of cases.

RESULTS

The expected number of cases in each district in a 6-month period was predicted using indicators from the previous 6-months and the estimated coefficients from the model. The model achieves an average of 90% predictive accuracy as measured by area under the receiver operating characteristic (ROC) curve, for the past 3 years of cases.

CONCLUSIONS

The risk of poliovirus has decreased dramatically in many of the key reservoir areas in Pakistan. The results of this model have been used to prioritize sub-national areas in Pakistan to receive additional immunization activities, additional monitoring, or other special interventions.

The role of supplementary environmental surveillance to complement acute flaccid paralysis surveillance for wild poliovirus in Pakistan - 2011-2013

Background

More than 99% of poliovirus infections are non-paralytic and therefore, not detected by acute flaccid paralysis (AFP) surveillance. Environmental surveillance (ES) can detect circulating polioviruses from sewage without relying on clinical presentation. With extensive ES and continued circulation of polioviruses, Pakistan presents a unique opportunity to quantify the impact of ES as a supplement to AFP surveillance on overall completeness and timeliness of poliovirus detection.

Methods

Genetic, geographic and temporal data were obtained for all wild poliovirus (WPV) isolates detected in Pakistan from January 2011 through December 2013. We used viral genetics to assess gaps in AFP surveillance and ES as measured by detection of ‘orphan viruses’ (≥1.5% different in VP1 capsid nucleotide sequence). We compared preceding detection of closely related circulating isolates (≥99% identity) detected by AFP surveillance or ES to determine which surveillance system first detected circulation before the presentation of each polio case.

Findings

A total of 1,127 WPV isolates were detected by AFP surveillance and ES in Pakistan from 2011–2013. AFP surveillance and ES combined exhibited fewer gaps (i.e., % orphan viruses) in detection than AFP surveillance alone (3.3% vs. 7.7%, respectively). ES detected circulation before AFP surveillance in nearly 60% of polio cases (200 of 346). For polio cases reported from provinces conducting ES, ES detected circulation nearly four months sooner on average (117.6 days) than did AFP surveillance.

Interpretation

Our findings suggest ES in Pakistan is providing earlier, more sensitive detection of wild polioviruses than AFP surveillance alone. Overall, targeted ES through strategic selection of sites has important implications in the eradication endgame strategy.

Eradication of measles: remaining challenges

Measles virus (MeV) is an aerosol-borne and one of the most contagious pathogenic viruses known. Almost every MeV infection becomes clinically manifest and can lead to serious and even fatal complications, especially under conditions of malnutrition in developing countries, where still 115,000 to 160,000 patients die from measles every year. There is no specific antiviral treatment. In addition, MeV infections cause long-lasting memory B and T cell impairment, predisposing people susceptible to opportunistic infections for years. A rare, but fatal long-term consequence of measles is subacute sclerosing panencephalitis. Fifteen years ago (2001), WHO has launched a programme to eliminate measles by a worldwide vaccination strategy. This is promising, because MeV is a human-specific morbillivirus (i.e. without relevant animal reservoir), safe and potent vaccine viruses are sufficiently produced since decades for common application, and millions of vaccine doses have been used globally without any indications of safety and efficacy issues. Though the prevalence of wild-type MeV infection has decreased by >90 % in Europe, measles is still not eliminated and has even re-emerged with recurrent outbreaks in developed countries, in which effective vaccination programmes had been installed for decades. Here, we discuss the crucial factors for a worldwide elimination of MeV: (1) efficacy of current vaccines, (2) the extremely high contagiosity of MeV demanding a >95 % vaccination rate based on two doses to avoid primary vaccine failure as well as the installation of catch-up vaccination programmes to fill immunity gaps and to achieve herd immunity, (3) the implications of sporadic cases of secondary vaccine failure, (4) organisation, acceptance and drawbacks of modern vaccination campaigns, (5) waning public attention to measles, but increasing concerns from vaccine-associated adverse reactions in societies with high socio-economic standards and (6) clinical, epidemiological and virological surveillance by the use of modern laboratory diagnostics and reporting systems. By consequent implementation of carefully designed epidemiologic and prophylactic measures, it should be possible to eradicate MeV globally out of mankind, as the closely related morbillivirus of rinderpest could be successfully eliminated out of the cattle on a global scale.

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.

Genomic Surveillance Elucidates Persistent Wild Poliovirus Transmission During 2013-2015 in Major Reservoir Areas of Pakistan

BACKGROUND

Despite tremendous efforts in the fight against polio, Pakistan bears the highest proportion of poliomyelitis cases among the 3 endemic countries including Afghanistan and Nigeria. Apart from insecurity and inaccessibility challenges, the substantial shift of unimmunized children from North Waziristan due to recent military operations was presumed to favor the widespread poliovirus infection in Pakistan.

METHODS

To better understand the current epidemiological situation, we analyzed the virologic data of wild poliovirus type 1 (WPV1) strains detected in Pakistan during 2013-2015.

RESULTS

Five genetic clusters (A-E) were identified with at least 5% nucleotide divergence in the viral protein 1 (VP1) coding region. Peshawar, Quetta, and Karachi were found to be the major endemic foci where multiple discrete genetic lineages of WPV1 were detected. Phylogenetic analysis suggests that wild poliovirus strains from endemic regions were genetically distant (with 5%-15% VP1 nucleotide divergence) from those detected in North Waziristan cases, excluding the possibility of a recent progenitor of WPV1 instigating single-source transmission across the country. Orphan lineages detected in Rawalpindi, Lahore, Hyderabad, Sukkur, and Jacobabad revealed silent transmission and the need for vigilant surveillance. Sustenance of analogous genetic lineages over a period of 3 years highlights multiple unimmunized foci present to maintain viral genetic diversity.

CONCLUSIONS

Our findings are inconsistent with the hypothesis that impoverished populations from North Waziristan serve as a possible determinant of widespread poliomyelitis infection in Pakistan and further emphasize the need to scale-up clinical and environmental surveillance as well as immunization activities.