Isolation of sabin-like polioviruses from wastewater in a country using inactivated polio vaccine

Detection of vaccine-derived poliovirus type 2 from sewage samples and public health response, Poland, November to December 2024

In October and December 2024, circulating vaccine-derived poliovirus type 2 (cVDPV2) was detected from two wastewater samples in Poland during routine environmental surveillance. The first isolate was characterised and matched previous cVDPV2 isolates detected in Spain in September, as well as in Germany, Finland, and the United Kingdom in November and December 2024. In response to the event, active surveillance for acute flaccid paralysis (AFP) has been strengthened, and the frequency of environmental sample collection has been increased.

Detection of circulating vaccine-derived poliovirus type 2 (cVDPV2) in wastewater samples: a wake-up call, Finland, Germany, Poland, Spain, the United Kingdom, 2024

In 2024, circulating vaccine-derived poliovirus type 2 (cVDPV2) was detected in wastewater samples in Finland, Germany, Poland, Spain and the United Kingdom (UK). All strains were genetically linked, but sequence analysis showed high genetic diversity among the strains identified within individual wastewater sites and countries and an unexpected high genetic proximity among isolates from different countries. Taken together these results, with sequential samples having tested positive in various sites, a broader geographic distribution beyond positive sampling sites must be considered.

Intensified Circulation of Echovirus 11 after the COVID-19 Pandemic in Poland: Detection of a Highly Pathogenic Virus Variant

After the first phase of the COVID-19 pandemic in Europe, a new highly pathogenic variant of echovirus 11 (E11) was detected. The aim of this study was to analyze the genetic diversity of Polish E11 environmental and clinical strains circulating between 2017 and 2023 as well as compare them with E11 strains isolated from severe neonatal sepsis cases reported in Europe between 2022 and 2023. Additionally, the study explores the effectiveness of environmental monitoring in tracking the spread of new variants. For this purpose, the complete sequences of the VP1 capsid protein gene were determined for 266 E11 strains isolated in Poland from 2017 to 2023, and phylogenetic analysis was performed. In the years 2017-2023, a significant increase in the detection of E11 strains was observed in both environmental and clinical samples in Poland. The Polish E11 strains represented three different genotypes, C3, D5 and E, and were characterized by a high diversity. In Poland, the intensive circulation of the new variant E11, responsible for severe neonatal infections with a high mortality in Europe, was detected in the years 2022-2023. This investigation demonstrates the important role of environmental surveillance in the tracking of enteroviruses circulation, especially in settings with limited clinical surveillance.

Sustained detection of type 2 poliovirus in London sewage between February and July, 2022, by enhanced environmental surveillance

BACKGROUND

The international spread of poliovirus exposes all countries to the risk of outbreaks and is designated a Public Health Emergency of International Concern by WHO. This risk can be exacerbated in countries using inactivated polio vaccine, which offers excellent protection against paralysis but is less effective than oral vaccine against poliovirus shedding, potentially allowing circulation without detection of paralytic cases for long periods of time. Our study investigated the molecular properties of type 2 poliovirus isolates found in sewage with an aim to detect virus transmission in the community.

METHODS

We performed environmental surveillance in London, UK, testing sewage samples using WHO recommended methods that include concentration, virus isolation in cell culture, and molecular characterisation. We additionally implemented direct molecular detection and determined whole-genome sequences of every isolate using novel nanopore protocols.

FINDINGS

118 genetically linked poliovirus isolates related to the serotype 2 Sabin vaccine strain were detected in 21 of 52 sequential sewage samples collected in London between Feb 8 and July 4, 2022. Expansion of environmental surveillance sites in London helped localise transmission to several boroughs in north and east London. All isolates have lost two key attenuating mutations, are recombinants with a species C enterovirus, and an increasing proportion (20 of 118) meet the criterion for a vaccine-derived poliovirus, having six to ten nucleotide changes in the gene coding for VP1 capsid protein.

INTERPRETATION

Environmental surveillance allowed early detection of poliovirus importation and circulation in London, permitting a rapid public health response, including enhanced surveillance and an inactivated polio vaccine campaign among children aged 1-9 years. Whole-genome sequences generated through nanopore sequencing established linkage of isolates and confirmed transmission of a unique recombinant poliovirus lineage that has now been detected in Israel and the USA.

FUNDING

Medicines and Healthcare products Regulatory Agency, UK Health Security Agency, Bill & Melinda Gates Foundation, and National Institute for Health Research Medical Research Council.

Investigation of airport sewage to detect importation of poliovirus, Poland, 2017 to 2020

BackgroundPolioviruses are human pathogens which may easily be imported via travellers from endemic areas and countries where oral polio vaccine (OPV) is still routinely used to polio-free countries. Risk of reintroduction strictly depends on polio immunisation coverage. Sustaining a polio-free status requires strategies that allow rapid detection and control of potential poliovirus reintroductions.AimThe aim of this study was to apply environmental surveillance at an international airport in Poland to estimate the probability of poliovirus importation via air transport.MethodsBetween 2017 and 2020, we collected 142 sewage samples at Warsaw Airport. After sewage concentration, virus was isolated in susceptible cell cultures. Poliovirus isolates were characterised by intratypic differentiation and sequencing.ResultsSeven samples were positive for polioviruses. All isolates were characterised as Sabin-like polioviruses type 3 (SL-3). No wild or vaccine-derived polioviruses were found. The number of mutations accumulated in most isolates suggested a limited circulation in humans. Only one SL-3 isolate contained seven mutations, which is compatible with more than half a year of circulation.ConclusionSince OPV was withdrawn from the immunisation schedule in Poland in 2016, detection of SL-3 in airport sewage may indicate the events of importation from a region where OPV is still in use. Our study shows that environmental surveillance, including airport sewage investigation, has the capacity to detect emerging polioviruses and monitor potential exposure to poliovirus importation. Poliovirus detection in sewage samples indicates the need for sustaining a high level of polio immunisation coverage in the population.

Efficacy of SARS-CoV-2 wastewater surveillance for detection of COVID-19 at a residential private college

Many colleges and universities utilized wastewater surveillance testing for SARS-CoV-2 RNA as a tool to help monitor and mitigate the COVID-19 pandemic on campuses across the USA during the 2020-2021 academic year. We sought to assess the efficacy of one such program by analyzing data on relative wastewater RNA levels from residential buildings in relation to SARS-CoV-2 cases identified through individual surveillance testing, conducted largely independent of wastewater results. Almost 80% of the cases on campus were associated with positive wastewater tests, resulting in an overall positive predictive value of 79% (Chi square 48.1, Df = 1, P < 0.001). However, half of the positive wastewater samples occurred in the two weeks following the return of a student to the residence hall following the 10-day isolation period, and therefore were not useful in predicting new infections. When these samples were excluded, the positive predictive value of a positive wastewater sample was 54%. Overall, we conclude that the continued shedding of viral RNA by patients past the time of potential transmission confounds the identification of new cases using wastewater surveillance, and decreases its effectiveness in managing SARS-CoV-2 infections on a residential college campus.

The role of genetic sequencing and analysis in the polio eradication programme

Genetic sequencing of polioviruses detected through clinical and environmental surveillance is used to confirm detection, identify their likely origin, track geographic patterns of spread, and determine the appropriate vaccination response. The critical importance of genetic sequencing and analysis to the Global Polio Eradication Initiative has grown with the increasing incidence of vaccine-derived poliovirus (VDPV) infections in Africa specifically (470 reported cases in 2019), and globally, alongside persistent transmission of serotype 1 wild-type poliovirus in Pakistan and Afghanistan (197 reported cases in 2019). Adapting what has been learned about the virus genetics and evolution to address these threats has been a major focus of recent work. Here, we review how phylogenetic and phylogeographic methods have been used to trace the spread of wild-type polioviruses and identify the likely origins of VDPVs. We highlight the analysis methods and sequencing technology currently used and the potential for new technologies to speed up poliovirus detection and the interpretation of genetic data. At a pivotal point in the eradication campaign with the threat of anti-vaccine sentiment and donor and public fatigue, innovation is critical to maintain drive and overcome the last remaining circulating virus.

Vaccine-Derived Poliovirus Infection among Patients with Primary Immunodeficiency and Effect of Patient Screening on Disease Outcomes, Iran

Patients with immunodeficiency-associated vaccine-derived poliovirus (iVDPV) are potential poliovirus reservoirs in the posteradication era that might reintroduce polioviruses into the community. We update the iVDPV registry in Iran by reporting 9 new patients. In addition to national acute flaccid paralysis surveillance, cases were identified by screening nonparalyzed primary immunodeficiency (PID) patients. Overall, 23 iVDPV patients have been identified since 1995. Seven patients (30%) never had paralysis. Poliovirus screening accelerated the iVDPV detection rate in Iran after 2014.The iVDPV infection rate among nonparalyzed patients with adaptive PID was 3.1% (7/224), several folds higher than previous estimates. Severe combined immunodeficiency patients had the highest risk for asymptomatic infection (28.6%) compared with other PIDs. iVDPV2 emergence has decreased after the switch from trivalent to bivalent oral poliovirus vaccine in 2016. However, emergence of iVDPV1 and iVDPV3 continued. Poliovirus screening in PID patients is an essential step in the endgame of polio eradication.

Environmental Surveillance for Poliovirus and Other Enteroviruses: Long-Term Experience in Moscow, Russian Federation, 2004⁻2017

Polio and enterovirus surveillance may include a number of approaches, including incidence-based observation, a sentinel physician system, environmental monitoring and acute flaccid paralysis (AFP) surveillance. The relative value of these methods is widely debated. Here we summarized the results of 14 years of environmental surveillance at four sewage treatment plants of various capacities in Moscow, Russia. A total of 5450 samples were screened, yielding 1089 (20.0%) positive samples. There were 1168 viruses isolated including types 1–3 polioviruses (43%) and 29 different types of non-polio enteroviruses (51%). Despite using the same methodology, a significant variation in detection rates was observed between the treatment plants and within the same facility over time. The number of poliovirus isolates obtained from sewage was roughly 60 times higher than from AFP surveillance over the same time frame. All except one poliovirus isolate were Sabin-like polioviruses. The one isolate was vaccine-derived poliovirus type 2 with 17.6% difference from the corresponding Sabin strain, suggesting long-term circulation outside the scope of the surveillance. For some non-polio enterovirus types (e.g., Echovirus 6) there was a good correlation between detection in sewage and incidence of clinical cases in a given year, while other types (e.g., Echovirus 30) could cause large outbreaks and be almost absent in sewage samples. Therefore, sewage monitoring can be an important part of enterovirus surveillance, but cannot substitute other approaches.

Poliovirus and Other Enteroviruses from Environmental Surveillance in Italy, 2009-2015

Within the initiatives for poliomyelitis eradication by WHO, Italy activated an environmental surveillance (ES) in 2005. ES complements clinical Acute Flaccid Paralysis (AFP) surveillance for possible polio cases, detects poliovirus circulation in environmental sewage, and is used to monitor transmission in communities. In addition to polioviruses, the analyses comprised: (i) the monitoring of the presence of non-polio enteroviruses in sewage samples and (ii) the temporal and geographical distribution of the detected viruses. From 2009 to 2015, 2880 sewage samples were collected from eight cities participating in the surveillance. Overall, 1479 samples resulted positive for enteroviruses. No wild-type polioviruses were found, although four Sabin-like polioviruses were detected. The low degree of mutation found in the genomes of these four isolates suggests that these viruses have had a limited circulation in the population. All non-polio enteroviruses belonged to species B and the most frequent serotype was CV-B5, followed by CV-B4, E-11, E-6, E-7, CV-B3, and CV-B2. Variations in the frequency of different serotypes were also observed in different seasons and/or Italian areas. Environmental surveillance in Italy, as part of the 'WHO global polio eradication program', is a powerful tool to augment the polio surveillance and to investigate the silent circulation or the re-emergence of enteroviruses in the population.

Isolation of Sabin-like Polioviruses from Sewage in Poland

As a complement to the active search for cases of acute flaccid paralysis, environmental sampling was conducted from January to December 2011, to test for any putative polio revertants and recombinants in sewage. A total of 165 environmental samples were obtained and analyzed for the presence of polioviruses by use of cell culture (L20B, RD and Caco-2) followed by neutralization and reverse-transcription polymerase chain reaction. Out of the 31 CPE positive samples, 26 contained one and 5 two different serotypes, yielding a total of 36 PVs. The microneutralization test revealed the presence of 7, 10 and 19 strains belonging to poliovirus serotype 1, 2 and 3, respectively. The genomic variability of 36 poliovirus strains was examined by the restriction fragment length polymorphism assay (RFLP). By combined analyses of two distant, polymorphic segments of the viral genome, one situated in the capsid protein VP1 coding region and the other in the 3D-polymerase coding region, we screened for the putative poliovirus revertants and recombinants. All detected PVs were classified as vaccine strains on the basis of RFLP-VP1 test. None of wild-type PVs or vaccine derived polioviruses were detected. RFLP assay also revealed the presence of 11 recombinants in 3D-polymerase coding region. Nine isolates appeared to be S3/S2, one S3/S1 and S1/S2 recombinant in analyzed 3Dpol region. This study revealed, through environmental monitoring, the introduction of SL PVs into the population associated with the routine use of OPV in Poland before the April 2016. Our findings demonstrate the usefulness of environmental surveillance in the overall polio eradication program.

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.

Laboratory Surveillance of Polio and Other Enteroviruses in High-Risk Populations and Environmental Samples

In the context of poliomyelitis eradication, a reinforced supplementary laboratory surveillance of enteroviruses was implemented in Greece. Between 2008 and 2014, the Hellenic Polioviruses/Enteroviruses Reference Laboratory performed detailed supplementary surveillance of circulating enteroviruses among healthy individuals in high-risk population groups, among immigrants from countries in which poliovirus is endemic, and in environmental samples. In total, 722 stool samples and 179 sewage water samples were included in the study. No wild-type polioviruses were isolated during these 7 years of surveillance, although two imported vaccine polioviruses were detected. Enterovirus presence was recorded in 25.3 and 25.1% of stool and sewage water samples, respectively. Nonpolio enteroviruses isolated from stool samples belonged to species A, B, or C; coxsackievirus A24 was the most frequently identified serotype. Only enteroviruses of species B were identified in sewage water samples, including four serotypes of echoviruses and four serotypes of coxsackie B viruses. Phylogenetic analysis revealed close genetic relationships among virus isolates from sewage water samples and stool samples, which in most cases fell into the same cluster. To the best of our knowledge, this is the first study to compare enterovirus serotypes circulating in fecal specimens of healthy individuals and environmental samples, emphasizing the burden of enterovirus circulation in asymptomatic individuals at high risk. Given that Greece continues to receive a large number of short-term arrivals, students, migrants, and refugees from countries in which poliovirus is endemic, it is important to guarantee high-quality surveillance in order to maintain its polio-free status until global eradication is achieved.IMPORTANCE This article summarizes the results of supplementary poliovirus surveillance in Greece and the subsequent characterization of enteroviral circulation in human feces and the environment. The examination of stool samples from healthy refugees and other individuals in "high-risk" groups for poliovirus enables the identification of enterovirus cases and forms the basis for further investigation of the community-level risk of viral transmission. In addition, the examination of composite human fecal samples through environmental surveillance links poliovirus and nonpoliovirus isolates from unknown individuals to populations served by the sewage or wastewater system. Supplementary surveillance is necessary to comply with the prerequisites imposed by the World Health Organization for monitoring the emergence of vaccine-derived polioviruses, reemergence of wild polioviruses, or disappearance of all vaccine-related strains in order for countries such as Greece to maintain their polio-free status and contribute to global poliovirus eradication.

Detection of Polioviruses in Sewage Using Cell Culture and Molecular Methods

The work presented here demonstrates the utility of a two-step algorithm for environmental poliovirus surveillance based on: preselection of sewage samples tested for the presence of enteroviral genetic material-RT-PCR assay and detection of infectious viruses by cell culture technique (L20B for polioviruses and RD for polio and other non-polio enteroviruses). RD and L20B cell lines were tested to determine their sensitivity for isolation of viruses from environmental samples (sewage). Finally, we wanted to determine if sewage concentration affects the results obtained for RT-PCR and cell cultures.

Contribution of Environmental Surveillance Toward Interruption of Poliovirus Transmission in Nigeria, 2012-2015

BACKGROUND

Cases of paralysis caused by poliovirus have decreased by >99% since the 1988 World Health Assembly's resolution to eradicate polio. The World Health Organization identified environmental surveillance (ES) of poliovirus in the poliomyelitis eradication strategic plan as an activity that can complement acute flaccid paralysis (AFP) surveillance. This article summarizes key public health interventions that followed the isolation of polioviruses from ES between 2012 and 2015.

METHODS

The grap method was used to collect 1.75 L of raw flowing sewage every 2-4 weeks. Once collected, samples were shipped at 4 °C to a polio laboratory for concentration. ES data were then used to guide program implementation.

RESULTS

From 2012 to 2015, ES reported 97 circulating vaccine-derived polioviruses (cVDPV2) and 14 wild polioviruses. In 2014 alone, 54 cVDPV type 2 cases and 1 WPV type 1 case were reported. In Sokoto State, 58 cases of AFP were found from a search of 9426 households. A total of 2 252 059 inactivated polio vaccine and 2 460 124 oral polio vaccine doses were administered to children aged <5 year in Borno and Yobe states.

CONCLUSIONS

This article is among the first from Africa that relates ES findings to key public health interventions (mass immunization campaigns, inactivated polio vaccine introduction, and strengthening of AFP surveillance) that have contributed to the interruption of poliovirus transmission in Nigeria.

Development of a multiplex RT-PCR assay for the identification of recombination types at different genomic regions of vaccine-derived polioviruses

Polioviruses (PVs) are the causal agents of acute paralytic poliomyelitis. Since the 1960s, poliomyelitis has been effectively controlled by the use of two vaccines containing all three serotypes of PVs, the inactivated poliovirus vaccine and the live attenuated oral poliovirus vaccine (OPV). Despite the success of OPV in polio eradication programme, a significant disadvantage was revealed: the emergence of vaccine-associated paralytic poliomyelitis (VAPP). VAPP is the result of accumulated mutations and putative recombination events located at the genome of attenuated vaccine Sabin strains. In the present study, ten Sabin isolates derived from OPV vaccinees and environmental samples were studied in order to identify recombination types located from VP1 to 3D genomic regions of virus genome. The experimental procedure that was followed was virus RNA extraction, reverse transcription to convert the virus genome into cDNA, PCR and multiplex-PCR using specific designed primers able to localize and identify each recombination following agarose gel electrophoresis. This multiplex RT-PCR assay allows for the immediate detection and identification of multiple recombination types located at the viral genome of OPV derivatives. After the eradication of wild PVs, the remaining sources of poliovirus infection worldwide would be the OPV derivatives. As a consequence, the immediate detection and molecular characterization of recombinant derivatives are important to avoid epidemics due to the circulation of neurovirulent viral strains.

Surveillance for parasites in unaccompanied minor refugees migrating to Germany in 2015

In 2015, most of the refugees arriving in Germany originated from countries with poor hygienic and sanitary conditions. Stool samples of 1,230 minor refugees unaccompanied by adults were investigated for possible parasites. Giardia lamblia was by far the most frequently detected parasite (n=165); all other parasites were considerably less frequent and encountered in the following order: Hymenolepis nana (n=23), Entamoeba histolytica (n=17), Trichuris trichiura (n=8), and Blastocystis hominis (n=1). Ascaris lumbricoides was not detected among any of the screened refugees. Considerable differences in prevalence rates in refugees originating from different countries could be observed.

Environmental Surveillance of Polioviruses in Rio de Janeiro, Brazil, in Support to the Activities of Global Polio Eradication Initiative

Wild polioviruses still remain endemic in three countries (Afghanistan, Pakistan, and Nigeria) and re-emergency of wild polio has been reported in previously polio-free countries. Environmental surveillance has been used as a supplementary tool in monitoring the circulation of wild poliovirus (PVs) and/or vaccine-derived PVs even in the absence of acute flaccid paralysis cases. This study aimed to monitor the presence of polioviruses in wastewater samples collected at one wastewater treatment plant located in the municipality of Rio de Janeiro, Brazil. From December 2011 to June 2012 and from September to December 2012, 31 samples were collected and processed. RD and L20B cell cultures were able to isolate PVs and non-polio enteroviruses in 27/31 samples. Polioviruses were isolated in eight samples (type 1 Sabin = 1, type 2 Sabin = 5, and type 3 Sabin = 2). Vaccine-derived polioviruses were not detected nor evidence of recombination with other PVs or non-polio enterovirus serotypes were observed among the isolates. The Sabin-related serotypes 2 and 3 presented nucleotide substitutions in positions associated with the neurovirulent phenotype at the 5'-UTR. Changes in important Amino acid residues at VP1 were also observed in the serotypes 2 and 3. Environmental surveillance has been used successfully in monitoring the circulation of PVs and non-polio enteroviruses and it is of crucial importance in the final stages of the WHO global polio eradication initiative. Our results show the continuous circulation of Sabin-like PVs and non-polio enteroviruses in the analyzed area during the study period.

Environmental Surveillance of Non-polio Enteroviruses in Poland, 2011

The aim of this study was to apply environmental surveillance to evaluate circulation of non-polio enteroviruses (NPEVs) in sewage in Poland. Samples of raw sewage were collected in 14 sewage disposal systems from January to December, 2011. Sewage samples were concentrated prior to analysis by RT-PCR and isolation in cells (RD, L20B and Caco-2). Out of the 165 analysed samples, 127 (77%) were positive for enteroviruses using RT-PCR and 109 (66%) were positive for enteroviruses using cell culture methods and the highest detection rate was observed in the summer and autumn. In total, 141 enteroviruses were identified using neutralization test (107 NPEVs and 34 polioviruses). Accounting for 52% of all the detected NPEVs, E11 and E3 were the predominant serotypes identified in raw sewage. Retrospectively, E11 was the known aetiology for the past aseptic meningitis outbreaks in Poland, as E3 being rarely associated with any outbreak prior to 2013. In conclusion, the environmental surveillance provides data which may help in understanding the epidemiology of enteroviruses in humans.

Sporadic isolation of sabin-like polioviruses and high-level detection of non-polio enteroviruses during sewage surveillance in seven Italian cities, after several years of inactivated poliovirus vaccination

Sewage surveillance in seven Italian cities between 2005 and 2008, after the introduction of inactivated poliovirus vaccination (IPV) in 2002, showed rare polioviruses, none that were wild-type or circulating vaccine-derived poliovirus (cVDPV), and many other enteroviruses among 1,392 samples analyzed. Two of five polioviruses (PV) detected were Sabin-like PV2 and three PV3, based on enzyme-linked immunosorbent assay (ELISA) and PCR results. Neurovirulence-related mutations were found in the 5'noncoding region (5'NCR) of all strains and, for a PV2, also in VP1 region 143 (Ile>Thr). Intertypic recombination in the 3D region was detected in a second PV2 (Sabin 2/Sabin 1) and a PV3 (Sabin 3/Sabin 2). The low mutation rate in VP1 for all PVs suggests limited interhuman virus passages, consistent with efficient polio immunization in Italy. Nonetheless, these findings highlight the risk of wild or Sabin poliovirus reintroduction from abroad. Non-polio enteroviruses (NPEVs) were detected, 448 of which were coxsackievirus B (CVB) and 294 of which were echoviruses (Echo). Fifty-six NPEVs failing serological typing were characterized by sequencing the VP1 region (nucleotides [nt] 2628 to 2976). A total of 448 CVB and 294 Echo strains were identified; among those strains, CVB2, CVB5, and Echo 11 predominated. Environmental CVB5 and CVB2 strains from this study showed high sequence identity with GenBank global strains. The high similarity between environmental NPEVs and clinical strains from the same areas of Italy and the same periods indicates that environmental strains reflect the viruses circulating in the population and highlights the potential risk of inefficient wastewater treatments. This study confirmed that sewage surveillance can be more sensitive than acute flaccid paralysis (AFP) surveillance in monitoring silent poliovirus circulation in the population as well as the suitability of molecular approaches to enterovirus typing.

Exposure factors for wastewater-irrigated Asian vegetables and a probabilistic rotavirus disease burden model for their consumption

Many farmers in water-scarce regions of developing countries use wastewater to irrigate vegetables and other agricultural crops, a practice that may expand with climate change. There are a number of health risks associated with wastewater irrigation for human food crops, particularly with surface irrigation techniques common in the developing world. The World Health Organization (WHO) recommends using quantitative microbial risk assessment (QMRA) to determine if the irrigation scheme meets health standards. However, only a few vegetables have been studied for wastewater risk and little information is known about the disease burden of wastewater-irrigated vegetable consumption in China. To bridge this knowledge gap, an experiment was conducted to determine volume of water left on Asian vegetables and lettuce after irrigation. One hundred samples each of Chinese chard (Brassica rapa var. chinensis), Chinese broccoli (Brassica oleracea var. alboglabra), Chinese flowering cabbage (Brassica rapa var. parachinensis), and lettuce (Lactuca sativa) were harvested after overhead sprinkler irrigation. Chinese broccoli and flowering cabbage were found to capture the most water and lettuce the least. QMRAs were then constructed to estimate rotavirus disease burden from consumption of wastewater-irrigated Asian vegetables in Beijing. Results indicate that estimated risks from these reuse scenarios exceed WHO guideline thresholds for acceptable disease burden for wastewater use, signifying that reduction of pathogen concentration or stricter risk management is necessary for safe reuse. Considering the widespread practice of wastewater irrigation for food production, particularly in developing countries, incorporation of water retention factors in QMRAs can reduce uncertainty regarding health risks for consumers worldwide.

Detection of Enteroviruses in Water Samples from Yopougon, Côte d'Ivoire by Cell Culture and Polymerase Chain Reaction

The objective of this study was to compare sensitivities of enterovirus isolation from wastewater in different cell lines as well as to compare the sensitivity and specificity of isolation in cell culture with direct detection by reverse transcription polymerase chain reaction (RT-PCR). Sixty-eight samples of wastewaters were collected between September 2008 and January 2009 in Yopougon, Abidjan. Enteroviruses were concentrated according to World Health Organization recommendations. Viruses were inoculated into various cell lines while direct RT-PCR was performed on water concentrates. The buffalo green monkey kidney cell line was the most sensitive with 58.8 % of viral isolation. This was followed by the rhabdomyosarcoma cell line with sensitivity of 51.6 %, with human epidermoid carcinoma cell line showing sensitivity of 50 % and fibroblastic cells derived from transgenic mice LTK-1 (L20B) cell showing 23.50 % sensitivity. However, a lower specificity of 2.9 % was observed with the L20B cell line. 44.1 % of the samples were positive by direct RT-PCR detection while 51.47 % samples were positive by using RT-PCR on infected cell cultures. No difference in percentage positivity was observed using RT-PCR on infected tissue culture isolates or using RT-PCR directly on wastewater samples.

Evolution and circulation of type-2 vaccine-derived polioviruses in Nad Ali district of Southern Afghanistan during June 2009-February 2011

Oral polio vaccine has been used successfully as a powerful tool to control the spread of wild polioviruses throughout the world; however, during replication in under immunized children, some vaccine viruses revert and acquire the neurovirulent phenotypic properties. In this study, we describe the evolution and circulation of Vaccine-Derived Polioviruses (VDPVs) in Helmand province of Afghanistan. We investigated 2646 AFP cases of Afghan children from June 2009-February 2011 and isolated 103 (04%) vaccine viruses, 45(1.7%) wild type polioviruses and six (0.22%) type 2 circulating vaccine-derived polioviruses (cVDPVs). These cVDPVs showed 97.7%-98.2% nucleotide and 98%-98.7% amino acid homology in VP1 region on comparison with Sabin type 2 reference strain. All these cVDPVs had two signature mutations of neurovirulent phenotypes and 12 additional mutations in P1 capsid region that might also have contributed to increase neurovirulence and replication. Phylogenetic analysis revealed that all these viruses were closely related and originated from previously reported Sabin like 2 virus from Pakistan which did not conform to the standard definition of VDPVs at that time. It was also observed that initial OPV dose was administered approximately 9 months prior to the collection of first stool specimen of index case. Our findings support that suboptimal surveillance and low routine immunization coverage have contributed to the emergence and spread of these viruses in Afghanistan. We therefore recommend high quality immunization campaigns not only in affected district Nad Ali but also in the bordering areas between Pakistan and Afghanistan to prevent the spread of cVDPVs.

Occurrence of human enteric viruses at freshwater beaches during swimming season and its link to water inflow

Human enteric viruses are significant etiological agents for many recreational waterborne illnesses. The occurrence and density of human enteric viruses such as human adenovirus (HAdV), human enterovirus (HEnV), and human norovirus genogroups I/II (HNoV GI/GII) were investigated using quantitative real-time PCR (qPCR) at freshwater beaches along with monitoring fecal indicators and environmental parameters. During the 2009 swimming season, water samples were collected from three inland freshwater beaches in Ohio, USA. Of the total samples, 40% (26/65) and 17% (11/65) were positive for HAdV and HEnV respectively, but HNoV GI/GII were not detected. There was no significant association among the detected human enteric viruses (HAdV and HEnV) and fecal bacteria indicators (Escherichia coli and Bacteroides) by Spearman correlation and principal component analyses. Logistic regression analysis also revealed that the odds of finding HAdV or HEnV was not influenced by levels of fecal bacteria indicators. However, there was a 14-fold increase in the odds of HEnV detection for each 1-log increase in daily water inflow (m(3)/s) into freshwater beach reservoirs (adjusted odds ratio=14.2; 95% confidence interval=1.19-171). In summary, the viral occurrence at the freshwater beaches was not readily explained by the levels of fecal bacteria indicators, but appeared to be more related to water reservoir inflows. These results suggest that hydrological data must be considered in future epidemiology efforts aimed at characterizing beach water safety.

Community circulation patterns of oral polio vaccine serotypes 1, 2, and 3 after Mexican national immunization weeks

BACKGROUND

With wild poliovirus nearing eradication, preventing circulating vaccine-derived poliovirus (cVDPV) by understanding oral polio vaccine (OPV) community circulation is increasingly important. Mexico, where OPV is given only during biannual national immunization weeks (NIWs) but where children receive inactivated polio vaccine (IPV) as part of their primary regimen, provides a natural setting to study OPV community circulation.

METHODS

In total, 216 children and household contacts in Veracruz, Mexico, were enrolled, and monthly stool samples and questionnaires collected for 1 year; 2501 stool samples underwent RNA extraction, reverse transcription, and real-time polymerase chain reaction (PCR) to detect OPV serotypes 1, 2, and 3.

RESULTS

OPV was detected up to 7 months after an NIW, but not at 8 months. In total, 35% of samples collected from children vaccinated the prior month, but only 4% of other samples, contained OPV. Although each serotype was detected in similar proportions among OPV strains shed as a result of direct vaccination, 87% of OPV acquired through community spread was serotype 2 (P < .0001).

CONCLUSIONS

Serotype 2 circulates longer and is transmitted more readily than serotypes 1 or 3 after NIWs in a Mexican community primarily vaccinated with IPV. This may be part of the reason why most isolated cVDPV has been serotype 2.

PCR assays for the identification of rare recombination types from VP1 to 3D genomic region of vaccine derived poliovirus strains

Poliomyelitis has been effectively controlled by the use of inactivated poliovirus vaccine (IPV) or trivalent live attenuated oral poliovirus vaccine (OPV). Since 1964, the use of OPV in mass vaccinations has resulted in drastic reductions of the number of poliomyelitis cases caused by wild-type polioviruses. However, the characterization of OPV derivatives with increased neurovirulence, constituted a real problem with respect to OPV safety. Mutations at attenuating sites of the genome and recombination events between Sabin strains of the trivalent OPV vaccine have been correlated with the loss of the attenuated phenotype of OPV strains and the acquisition of traits characteristic of wild polioviruses. In consequence, early detection and characterization of recombinant evolved derivatives of vaccine strains is highly important. In this report, ten PCR assays are described which allow for the identification of rare recombination events located in VP1, 2A, 2C, 3A, 3C and 3D genomic regions and predominant recombination events located in 2C and 3D genomic regions of OPV derivatives. These assays could be readily implemented in diagnostics laboratories lacking sequencing facilities as a first approach for the early detection and characterization of recombinant OPV derivatives.

Interaction of Paramecium caudatum and Picornaviruses

In our paper we have researched the relationship between picornaviruses (poliovirus, foot-and-mouth disease virus and encephalomyocarditis virus) and Ciliata (Paramecium caudatum). We show that the number of Paramecium in medium sharply increased during coincubation with picornaviruses within 2-5 days. This cannot be explained only by the fact that viruses were nutrient source for Paramecium because in case of inactivated viruses the number of infusorians in medium increased a little. At the same time the titer of viruses harshly decreased whereas in the control group, which is free of Paramecium, the fall of titer was little. Picornaviruses were eliminated from medium if only living Parameciums were present in medium. After 7-9 days of coincubation only a few number of viruses were liberated from destroyed Parameciums. These results will be especially useful for management of reservoirs of picornaviruses in water and prevention of diseases.

Development of real-time PCR to detect oral vaccine-like poliovirus and its application to environmental surveillance

In order to perform environmental surveillance to track oral poliovirus vaccine-like poliovirus sensitively and conveniently, real-time PCR was developed and applied to a raw sewage concentrate. The real-time PCR method detected 0.01-0.1 TCID50 of 3 serotypes of Sabin strain specifically. The method also detected the corresponding serotypes of oral poliovirus vaccine-like poliovirus specifically, but detected neither wild poliovirus, except Mahoney for type 1 and Saukett for type 3, nor other enteric viruses, as far as examined. When real-time PCR was applied to environmental surveillance, the overall agreement rates between real-time PCR and the cell culture were 83.3% for all serotypes. Since real-time PCR has the advantages of rapid detection of viruses and minimum requirement of sampling volume as compared with ordinary cell culture, it is suitable to monitor oral poliovirus vaccine-like poliovirus in the environment, especially in areas where an oral vaccine is being replaced by an inactivated vaccine.

Genetic analysis of poliovirus strains isolated from sewage in Poland

The study describes genetic characterization of poliovirus (PV) strains isolated from sewage samples in Poland. The analyses were performed for the detection of any putative polio revertants and recombinants in three genomic regions by sequencing analysis. Thirty-six strains were analyzed. The analyzed strains were identified by neutralization assay as 7 strains of serotype P1, 10 strains of serotype P2, and 19 strains of serotype P3. Sewage isolates were sequenced in 5'UTR, VP1, and 3D genomic regions. All detected PVs were classified as vaccine strains on the basis of VP1 sequence. Mutational differences in the VP1 sequences of isolated viruses ranged from 0.0% to 0.4%, indicating a limited replication period. The genetic analysis of the 3D region showed that some strains have recombinant genomes. Nine strains were found as dipartite recombinants (seven strains--S3/S2, one strain--S2/S1, one strain--S3/S1), while one strain was found as tripartite recombinant (S3/S2/S1). No recombinants with non-PV enteroviruses were identified. None of wild-type PVs or vaccine-derived polioviruses (VDPVs) were detected. This study showed the absence of wild or VDPV circulation in the country and demonstrated the usefulness of environmental surveillance in addition to acute flaccid paralysis (AFP) surveillance in support of polio eradication initiatives.

Detection and distribution of culturable Human Enteroviruses through environmental surveillance in Milan, Italy

AIMS

Human Enteroviruses (HEVs) infections have a significant impact on public health, being implicated in outbreaks of meningitis, encephalitis, hand-foot-mouth disease and other acute and chronic manifestation. In the strategic plan for poliomyelitis eradication, the environmental surveillance of poliovirus (PV) has been identified by the World Health Organization (WHO) as an activity that can complement the surveillance of polio. Having wastewater samples available for PV surveillance allows us to study nonpolio enteroviruses (NPEVs) circulating in the study population, which are widely spread.

METHODS AND RESULTS

This study was carried out according to the WHO guidelines for environmental surveillance of PV and analysed the circulation of PV and NPEVs through the isolation of viruses in cell cultures in Milan area; from 2006 to 2010, 321 wastewater samples were collected, regularly over time, at the inlet of three diverse waste water treatment plants (WWTPs). Culturable HEVs were isolated in 80% of sewage samples: all isolates belonged to the HEV-B group and those circulating more intensely were CVB5 and Echo 6, while CVB4 was the predominant serotype found in 2010. In this study, two type 2 PVs were isolated, both characterized as Sabin like.

CONCLUSION

Environmental monitoring of HEVs in Milan has proved to be an interesting tool to investigate the circulation and distribution of viruses.

SIGNIFICANCE AND IMPACT OF THE STUDY

The detection of PV and other NPEV could be predictive of possible re-emergence of these viruses with an impact on public health. NPEV monitoring could also be a powerful public health tool to investigate the possible role of NPEV in different clinical manifestations.

The final stages of the global eradication of poliomyelitis

The global incidence of poliomyelitis has dropped by more than 99 per cent since the governments of the world committed to eradication in 1988. One of the three serotypes of wild poliovirus has been eradicated and the remaining two serotypes are limited to just a small number of endemic regions. However, the Global Polio Eradication Initiative (GPEI) has faced a number of challenges in eradicating the last 1 per cent of wild-virus transmission. The polio endgame has also been complicated by the recognition that vaccination with the oral poliovirus vaccine (OPV) must eventually cease because of the risk of outbreaks of vaccine-derived polioviruses. I describe the major challenges to wild poliovirus eradication, focusing on the poor immunogenicity of OPV in lower-income countries, the inherent limitations to the sensitivity and specificity of surveillance, the international spread of poliovirus and resulting outbreaks, and the potential significance of waning intestinal immunity induced by OPV. I then focus on the challenges to eradicating all polioviruses, the problem of vaccine-derived polioviruses and the risk of wild-type or vaccine-derived poliovirus re-emergence after the cessation of oral vaccination. I document the role of research in the GPEI's response to these challenges and ultimately the feasibility of achieving a world without poliomyelitis.

Human enterovirus surveillance in the Slovak Republic from 2001 to 2011

We report the outcome of an 11-year programme monitoring sewage water and acute flaccid paralysis (AFP) cases as part of the World Health Organization (WHO) strategy for polio eradication in the Slovak Republic (SR). Polioviruses (PV) and non-polio enteroviruses (NPEV), prior to and after the change in polio vaccination strategy, were detected. Sewage treatment plant samples from 48 localities spread over the Western, Central and Eastern regions and clinical material from AFP cases were examined. The WHO standard procedures were followed with regard to virus isolation and identification. There were 538 commonly detected human enteroviruses (HEVs) including 213 (40%) coxsackie B viruses (CBV), 200 (37%) echoviruses and 113 (21%) Sabin-like PVs (PV1, 2, 3) including vaccine-derived poliovirus (VDPV) isolates. The percentage of PV isolates fell from 66% to 30% during 2001-2005 and thereafter fell to zero. CBV5, CBV2 and echovirus 3 were the NPEVs endemic during the study period.

A genotype of modified vaccinia Ankara (MVA) that facilitates replication in suspension cultures in chemically defined medium

While vectored vaccines, based on hyperattenuated viruses, may lead to new treatment options against infectious diseases and certain cancers, they are also complex products and sometimes difficult to provide in sufficient amount and purity. To facilitate vaccine programs utilizing host-restricted poxviruses, we established avian suspension cell lines (CR and CR.pIX) and developed a robust, chemically defined, culturing process for production of this class of vectors. For one prominent member, modified vaccinia Ankara (MVA), we now describe a new strain that appears to replicate to greater yields of infectious units, especially in the cell-free supernatant of cultures in chemically defined media. The new strain was obtained by repeated passaging in CR suspension cultures and, consistent with reports on the exceptional genetic stability of MVA, sequencing of 135 kb of the viral genomic DNA revealed that only three structural proteins (A3L, A9L and A34R) each carry a single amino acid exchange (H639Y, K75E and D86Y, respectively). Host restriction in a plaque-purified isolate of the new genotype appears to be maintained in cell culture. Processing towards an injectable vaccine preparation may be simplified with this strain as a complete lysate, containing the main burden of host cell contaminants, may not be required anymore to obtain adequate yields.

Risks associated with the use of live-attenuated vaccine poliovirus strains and the strategies for control and eradication of paralytic poliomyelitis

The Global Polio Eradication Initiative was launched in 1988 with the aim to eliminate paralytic poliomyelitis. Two effective vaccines are available: inactivated polio vaccine (IPV) and oral polio vaccine (OPV). Since 1964, OPV has been used instead of IPV in most countries due to several economic and biological advantages. However, in rare cases, the live-attenuated Sabin strains of OPV revert to neurovirulence and cause vaccine-associated paralytic poliomyelitis in vaccinees or lead to emergence of vaccine-derived poliovirus strains. Attenuating mutations and recombination events have been associated with the reversion of vaccine strains to neurovirulence. The substitution of OPV with an improved new-generation IPV and the availability of new specific drugs against polioviruses are considered as future strategies for outbreak control and the eradication of paralytic poliomyelitis worldwide.

The double-edged sword: How evolution can make or break a live-attenuated virus vaccine

Even students who reject evolution are often willing to consider cases in which evolutionary biology contributes to, or undermines, biomedical interventions. Moreover the intersection of evolutionary biology and biomedicine is fascinating in its own right. This review offers an overview of the ways in which evolution has impacted the design and deployment of live-attenuated virus vaccines, with subsections that may be useful as lecture material or as the basis for case studies in classes at a variety of levels. Live- attenuated virus vaccines have been modified in ways that restrain their replication in a host, so that infection (vaccination) produces immunity but not disease. Applied evolution, in the form of serial passage in novel host cells, is a "classical" method to generate live-attenuated viruses. However many live-attenuated vaccines exhibit reversion to virulence through back-mutation of attenuating mutations, compensatory mutations elsewhere in the genome, recombination or reassortment, or changes in quasispecies diversity. Additionally the combination of multiple live-attenuated strains may result in competition or facilitation between individual vaccine viruses, resulting in undesirable increases in virulence or decreases in immunogenicity. Genetic engineering informed by evolutionary thinking has led to a number of novel approaches to generate live-attenuated virus vaccines that contain substantial safeguards against reversion to virulence and that ameliorate interference among multiple vaccine strains. Finally, vaccines have the potential to shape the evolution of their wild type counterparts in counter-productive ways; at the extreme vaccine-driven eradication of a virus may create an empty niche that promotes the emergence of new viral pathogens.

Spatiotemporal phylogenetic analysis and molecular characterization of coxsackievirus A4

Coxsackievirus A4 outbreaks occurred in Taiwan in 2004 and 2006. The spatiotemporal transmission of this error-prone RNA virus involves a continuous interaction between rapid sequence variation and natural selection. To elucidate the molecular characteristics of CV-A4 and the spatiotemporal dynamic changes in CV-A4 transmission, worldwide sequences of the 3' VP1 region (420 nt) obtained from GenBank were analyzed together with sequences isolated in Taiwan from 2002 to 2009. Sequences were characterized in terms of recombination, variability, and selection. Phylogenetic trees were constructed using neighbor-joining, maximum likelihood and Monte Carlo Markov Chain methods. Spatiotemporal dynamics of CV-A4 transmission were further estimated by a Bayesian statistical inference framework. No recombination was detected in the 420 nt region. The estimated evolution rate of CV-A4 was 8.65 × 10(-3) substitutions/site/year, and a purifying selection (d(N)/d(S)=0.032) was noted over the 3' VP1 region. All trees had similar topology: two genotypes (GI and GII), each including two subgenotypes (A and B), with the prototype and a Kenyan strain in separate branches. The results revealed that the virus first appeared in USA in 1950. Since 1998, it has evolved into the Kenya, GI-A (Asia) and GII-A (Asia and Europe) strains. Since 2004, GI-B and GII-B have evolved continuously and have remained prevalent. The co-existence of several positive selection lineages of GI-B in 2006 indicates that the subgenotype might have survived lineage extinction. This study revealed rapid lineage turnover of CV-A4 and the replacement of previously circulating strains by a new dominant variant. Therefore, continuous surveillance for further CV-A4 transmission is essential.

Contribution of treated wastewater to the microbiological quality of Seine River in Paris

Urban part of Seine River serving as drinking water supply in Paris can be heavily contaminated by Cryptosporidium spp. and Giardia duodenalis. In the absence of agricultural practice in this highly urbanized area, we investigated herein the contribution of treated wastewater to the microbiological quality of this river focusing on these two parasites. Other microorganisms such as faecal bacterial indicators, enteroviruses and oocysts of Toxoplasma gondii were assessed concurrently. Raw wastewaters were heavily contaminated by Cryptosporidium and Giardia (oo)cysts, whereas concentrations of both protozoa in treated wastewater were lower. Treated wastewater, flowed into Seine River, had a parasite concentration closed to the one found along the river, in particular at the entry of a drinking water plant (DWP). Even if faecal bacteria were reliable indicators of a reduction in parasite concentrations during the wastewater treatment, they were not correlated to protozoal contamination of wastewater and river water. Oocysts of T. gondii were not found in both raw and treated wastewater, or in Seine River. Parasitic contamination was shown to be constant in the Seine River up to 40 km upstream Paris. Altogether, these results strongly suggest that treated wastewater does not contribute to the main parasitic contamination of the Seine River usually observed in this urbanized area.

Recurrent isolation of poliovirus 3 strains with chimeric capsid protein Vp1 suggests a recombination hot-spot site in Vp1

Five oral poliovirus vaccine (OPV) strains carrying an intertypic PV3/PV2 recombination in VP1 capsid protein were isolated during poliovirus surveillance. These five PV3 strains had altogether four diverse recombination crossover points near the 3' end of the VP1 coding region. The complete antigenic site IIIa was replaced by PV2-specific amino acids in four of the studied PV3 strains. Low overall number of nucleotide substitutions in VP1 indicated that the predicted replication time, "age", of the PV3 strains was short, 6 months or less. The nucleotide 472-T in the 5' non-coding region, associated to the attenuated phenotype of PV3/Sabin, was reverted to wild-type C in all studied PV3/PV2 recombinant strains. Three of the PV3 strains had at least a tripartite genome deduced from the partial 3D polymerase-coding region sequences. Our results suggest that there exists a PV3/PV2 recombination hot-spot site in the 3' partial region of the VP1 capsid protein and that the recombination may occur within weeks or a few months after the administration of OPV.