Antigenic and molecular characterization of wild type 1 poliovirus causing outbreaks of poliomyelitis in Albania and neighboring countries in 1996

Detection of Echovirus 11 lineage 1 in wastewater samples in Sicily

We report the presence of Echovirus 11 (E11) in wastewater in Sicily (Southern Italy), since August 2022. Overall, the 5.4 % of sewage samples (7/130) collected in 2022 were positives for E11 and then the percentage of E11-positive sewage samples reached the value of 27.27(18/66) in the first semester of 2023. Phylogenetic analysis of VP1 sequences showed for most E11-positive samples (16/25: 64 %) close genetic correlation (98.4-99.4 % nucleotide identity) to E11 lineage 1 strains involved in recently reported severe neonatal infections.

Were there long-term economic effects of exposure to polio vaccination? An analysis of migrants to Sweden 1946-2003

Recent research showed that exposure to the vaccine against polio in early life had no long-term economic benefits among native Swedes. However, whether this result holds for individuals from other countries remains unexplored. This study explores the relationship between exposure to the vaccine and later-life outcomes, but focuses on individuals who migrated to Sweden (birth cohorts 1946-1971), and constitute a diverse sample in terms of national origin. Using a differences-in-differences approach and register data from the Swedish Longitudinal Immigrant Database, this study explores if being exposed to the vaccine against polio in the year of birth in the country of origin has any impact on adult income, educational achievement, or days or number of hospitalizations. The results are in line with the previous research in showing that there are no statistically significant effects on adult income, education, or health from exposure to the vaccine against polio, regardless of national origin. Furthermore, no scarring effects of exposure to polio epidemics were found on any of the outcomes, reinforcing the hypothesis that polio did not scar individuals in the same way as other contemporary epidemic diseases did, and that the lack of scarring could explain the absence of long-term impact from vaccine exposure.

Characterizing poliovirus transmission and evolution: insights from modeling experiences with wild and vaccine-related polioviruses

With national and global health policymakers facing numerous complex decisions related to achieving and maintaining polio eradication, we expanded our previously developed dynamic poliovirus transmission model using information from an expert literature review process and including additional immunity states and the evolution of oral poliovirus vaccine (OPV). The model explicitly considers serotype differences and distinguishes fecal-oral and oropharyngeal transmission. We evaluated the model by simulating diverse historical experiences with polioviruses, including one country that eliminated wild poliovirus using both OPV and inactivated poliovirus vaccine (IPV) (USA), three importation outbreaks of wild poliovirus (Albania, the Netherlands, Tajikistan), one situation in which no circulating vaccine-derived polioviruses (cVDPVs) emerge despite annual OPV use and cessation (Cuba), three cVDPV outbreaks (Haiti, Madura Island in Indonesia, northern Nigeria), one area of current endemic circulation of all three serotypes (northern Nigeria), and one area with recent endemic circulation and subsequent elimination of multiple serotypes (northern India). We find that when sufficient information about the conditions exists, the model can reproduce the general behavior of poliovirus transmission and outbreaks while maintaining consistency in the generic model inputs. The assumption of spatially homogeneous mixing remains a significant limitation that affects the performance of the differential equation-based model when significant heterogeneities in immunity and mixing may exist. Further studies on OPV virus evolution and improved understanding of the mechanisms of mixing and transmission may help to better characterize poliovirus transmission in populations. Broad application of the model promises to offer insights in the context of global and national policy and economic models.

Interrupting wild poliovirus transmission using oral poliovirus vaccine: environmental surveillance in high-risks area of India

Global eradication of poliomyelitis has reached critical stage. Sabin Oral Poliovirus Vaccine (OPV) has been successful in three major regions of the world. In India eradication of poliomyelitis from states of Uttar Pradesh (UP) and Bihar has been difficult due to high population and low-socioeconomic standards of living. Acute flaccid paralysis (AFP) surveillance and intensive OPV rounds continues with the World Health Organization (WHO) operational strategies. Yet apparent lack of progress in reducing the number of wild cases has resulted in occasional impatience and frustration, even leading to questions about ultimate feasibility of global eradication using OPV. Lucknow in UP is in geographical area endemic for poliomyelitis and is surrounded by high-risk areas yet maintains a polio-free status since 2002. Environmental surveillance study was conducted (2004-2006) to authenticate the decline in the wild poliovirus (PV) cases in Lucknow. Sewage sample analyses were compared with stools of AFP patients and healthy children from same geographical area. Study reveals useful information on OPV circulation and proves important epidemiological tool to trust WHO's OPV immunization program. Genetic sequencing had detected silent wild PV-1 circulation of RCP1PGI (EU049849), RCP2PGI (EU049850), RCP3PGI (EU049851), and RCP4PGI (EU049852) in sewage waters. Properties of isolates from sewage reflected those of viruses excreted from human. This study provides valuable information and encouragement to AFP surveillance to maintain high levels of OPV immunization campaigns in the most difficult endemic region of India to interrupt the wild PV transmission.

Recombinant Sabin environmental isolates in Greece and Cyprus

AIMS

Twenty-one polioviruses (PVs) Sabin strains were isolated from sewage treatment plants from Metamorphosis, Athens, Greece during the time period from May to October 1996, and from two other sites located at Nicosia and Limassol in Cyprus between April and December 2003 were retrospectively investigated for the detection of recombinant PVs.

METHODS AND RESULTS

Three PVs isolates were found as tripartite recombinants, S3/S2/S1 in the 2C genomic viral region. The first recombination site S3/S2 was located close to the 5' end of 2C while the second recombination site S2/S1 was located towards the 3' end of 2C. Such recombination is a rare event producing a tripartite hybrid 2C protein. Three more PVs isolates were characterized as bipartite S2/S1 recombinants and one as S2/S3 bipartite recombinant.

CONCLUSIONS

Detection of recombinant circulating vaccine-derived PVs (cVDPVs) is crucial, since increased transmissibility over that of the parental Sabin strains has been proposed to be the result of recombination events.

SIGNIFICANCE AND IMPACT OF THE STUDY

Importation of recombinant cVDPVs evolved derivatives pose a serious threat to public health and environmental surveillance should be implemented during and after PVs eradication.

Poliovirus vaccine strains in sewage and river water in South Africa

Since the initiation of the global poliomyelitis eradication program in 1988, the number of wild-type polio cases decreased from 350,000 to fewer than 500, and the number of polio endemic countries declined from more than 125 to 10. The last case of polio in South Africa caused by a wild-type poliovirus (PV) occurred in 1989. The live attenuated oral poliovirus vaccine (OPV) has been effectively used in the reduction and control of poliomyelitis. However, as OPV strains are excreted in stools after vaccination, this vaccine could become a source of dissemination of PVs in the environment and the potential cause of poliomyelitis. Therefore, the aim of the study was to determine the occurrence of OPV strains in selected sewage and river water samples. During the period between 2001 and 2003, 138 samples of river water and 213 samples of settled sewage were collected from selected areas of South Africa. A total of 860 plaques were analysed, which consisted of 703 plaques from the sewage and 157 plaques from the river water samples. Using a reverse transcriptase (RT)-multiplex PCR, 49 PVs were successfully distinguished from 176 non-polio enteroviruses (NPEVs). The 176 NPEVs consisted of 50 coxsackie B2 viruses (CBV2), followed by 39 echoviruses 11 (ECV11), 25 CBV5, 21 CBV3, 15 CBV4, 14 coxsackie A6 viruses (CAV6), 7 CBV6, 2 CAV5, 2 CBV1, and 1 ECV19, which was in agreement with the prevalence of these EVs in other parts of the world. The Sabin-specific RT-triplex PCR revealed the presence of 29 Sabin PV type 1, 8 Sabin PV type 2, and 12 Sabin PV type 3 isolates. Buffalo green monkey kidney and primary liver carcinoma cell cultures allowed the amplification of a broad spectrum of EVs, whereas human epidermoid carcinoma cells were more selective for PVs. This study addressed some of the issues regarding the prevalence of OPV strains in the environment. The identification of 49 viable OPV isolates confirmed the presence and circulation of PV vaccine strains in sewage and river water. The extent of the potential health risk constituted by these OPV isolates remains to be investigated.

Molecular characterization of wild-type polioviruses isolated in Greece during the 1996 outbreak in Albania

During the present study three type 1 poliovirus strains isolated in Greece during the 1996 poliomyelitis outbreak in Albania were retrospectively investigated and determination of their relationship with other epidemic strains isolated in Albania or elsewhere during previous epidemics was attempted. SimPlot analysis revealed that the three Greek strains are the result of a recombination event in the VP2 coding region.

Molecular mechanisms of poliovirus variation and evolution

Replication of poliovirus RNA is accomplished by the error-prone viral RNA-dependent RNA polymerase and hence is accompanied by numerous mutations. In addition, genetic errors may be introduced by nonreplicative mechanisms. Resulting variability is manifested by point mutations and genomic rearrangements (e.g., deletions, insertions and recombination). After description of basic mechanisms underlying this variability, the review focuses on regularities of poliovirus evolution (mutation fixation) in tissue cultures, human organisms and populations.

A dynamic model of poliomyelitis outbreaks: learning from the past to help inform the future

Policy-makers now face important questions regarding the tradeoffs among different strategies for managing poliomyelitis risks after they succeed with polio eradication. To estimate the potential consequences of reintroductions of polioviruses and the resulting outbreaks, the authors developed a dynamic disease transmission model that can simulate many aspects of outbreaks for different posteradication conditions. In this paper, the authors identify the issues related to prospective modeling of future outbreaks using such a model, including the reality that accurate prediction of conditions and associated model inputs prior to future outbreaks remains challenging. The authors explored the model's behavior in the context of three recent outbreaks resulting from importation of poliovirus into previously polio-free countries and found that the model reproduced reported data on the incidence of cases. The authors expect that this model can provide important insights into the dynamics of future potential poliomyelitis outbreaks and in this way serve as a useful tool for risk assessment.

Vaccination coverage among adolescents in certain provinces of Greece

AIM

To estimate the vaccination coverage in a sample of adolescents in Greece.

METHODS

Vaccination status was estimated in 483 adolescents aged 15-19 y in four prefectures. The criteria for full vaccination were based on the recommendations of the Greek National Vaccination Schedule.

RESULTS

The participation rate in the study was 78.7% (380/483 adolescents). The rates of full vaccination were 94.2% for poliomyelitis, 78.4% for hepatitis B, 77.4% for BCG, 65.0% for tetanus and 54.4% for diphtheria. The rates of full vaccination for measles, rubella and mumps were 65.0%, 57.6%, and 56.0%, respectively. For pertussis, the full vaccination rate was only 36.0%, and 7.1% of the study population was totally unvaccinated. The most missed dose for all vaccines was the final booster dose, which is usually administered in older children or adolescents.

CONCLUSION

Adolescent vaccination coverage was not satisfactory in this study, mainly due to non-compliance to the final booster dose. Completion of missing vaccines at this age represents the last opportunity for massive intervention and would be of essential value for individual and community protection against common preventable diseases.

A seroprevalence study of poliovirus antibody in the population of northern Greece

This study assessed immunity to poliomyelitis in a representative sample of 1064 persons living in northern Greece. Antibody prevalences in the individuals tested were 91.1% (95% confidence interval (CI): 89.4-92.8), 92.1% (95% CI: 90.5-93.7) and 83.1% (95% CI: 80.8-85.4) for poliovirus types 1, 2 and 3, respectively. For poliovirus type 3, a gap in immunity was found in individuals aged 10-29 years. Re-vaccination of adolescents living in northern Greece is suggested to ensure herd immunity and to minimise the risk of importation of wild poliovirus from endemic countries.

Analysis of antigenic profiles of inactivated poliovirus vaccine and vaccine-derived polioviruses by block-ELISA method

A new block-ELISA test for quantitative evaluation of relative reactivity of antigenic sites was developed and used to reveal the detailed epitope structure of inactivated poliovirus vaccines (IPV) and live poliovirus strains. Poliovirus was captured on ELISA plates coated with rabbit anti-poliovirus IgG and blocked by monoclonal antibodies (Mabs) specific to individual epitopes before the remaining reactive antigenic sites were quantified by polyclonal anti-poliovirus IgG conjugate. The decrease of conjugate binding by the pre-treatment with a Mab reflects its contribution to the overall reactivity of poliovirus antigen. The level of block activity of Mabs for a given antigen can be expressed as a percent of reduction of antigenic reactivity as determined by ELISA test. It can be normalized by expressing this value as a ratio to the block activity of a reference sample. The data on the blocking-activity of a panel of monoclonal antibodies specific to different antigenic sites represents the epitope composition (antigenic profile) of a sample. Quantitative differences in epitope composition were determined for nine samples of inactivated poliovirus vaccine (IPV) and compared with the International Reference Reagent. This method could be used for monitoring consistency of IPV production, comparison of vaccines made by different manufacturers, and for the analysis of antigenically modified strains of attenuated poliovirus. Antigenic structures of two isolates of type 1 vaccine-derived poliovirus (VDPV) were compared with the structures of parental Sabin 1 and wild-type Mahoney strains using 17 monoclonal antibodies and revealed significant differences, suggesting that the method can be used for screening of field isolates and rapid identification of antigenically divergent VDPV strains.

Poliovirus sampling by using sodium dodecyl sulfate/EDTA-pretreated chromatography paper strips

To achieve the goal of poliovirus eradication, surveillance of endemic areas is a crucial step in the poliovirus eradication program. Currently, six countries still have endemic poliovirus. We have tested a novel method which uses SDS/EDTA-treated chromatography paper strips to collect and transport poliovirus-containing stool samples. The SDS/EDTA-treated paper strips were soaked with different dilutions of poliovirus-containing feces and stored at different temperatures. After storing the SDS/EDTA paper strips for 5 months at 37 degrees C, poliovirus RNA could be successfully amplified using RT-PCR. Infectivity of wild-type poliovirus type 1, 2, and 3 was lost upon contact with the SDS/EDTA-treated strips. This easy, inexpensive, and biosafe chromatography paper strip method for the collection and transportation of poliovirus samples can be of use in poliovirus surveillance and polio vaccination programs.

Retrospective study on poliomyelitis cases in northern Greece

Here we report the results of a retrospective study on the epidemiological characteristics and genetic relationships of the virus isolates responsible for the last poliomyelitis cases in Greece. The last wild poliomyelitis case in Greece was detected in 1996, and the last vaccine-related strain was isolated in 1998. The whole of Europe, including Greece, is now considered to be polio-free.

Phylogenetic analysis of wild-type 1 polioviruses isolated during the final period of transmission in Turkey

The last poliomyelitis case associated with a wild poliovirus in Turkey occurred in November 1998. This was the last known case of paralytic poliomyelitis caused by indigenous wild poliovirus in the World Health Organization's European Region. This study investigated the genetic relationships of wild-type 1 polioviruses at the latest period of transmission. A phylogenetic tree was constructed on the basis of the VP1/2A sequence from 14 wild-type 1 polioviruses isolated from Turkey in 1994–1998, along with those from other areas of the world. The Turkey isolates in the latest period of transmission were closely related to each other, forming a cluster distinct from other strains. The results showed that these viruses had been spreading indigenously in the eastern and south-eastern parts of Turkey, and ceased transmission there during 1998. This finding serves as a reference for future poliovirus surveillance both in Turkey and worldwide.

Immunity to diphtheria among refugees in southern Italy

This study assessed the immune status against diphtheria of a sample of refugees (mainly Kosovars and Kurds) in southern Italy (Puglia). The 54.8% of 1128 subjects showed full protection against diphtheria, 30.1% had basic protection and 15.1% resulted seronegative for antitoxin antibody. Only from 45.9 to 73.9% of 0-10 years old refugees were fully protected while from 12.3 to 24.2% were seronegative to diphtheria with the poorest protection rate among Kurdish children from Turkey. Kosovars showed the highest protection rate to diphtheria whereas data suggest a probable endemic level of diphtheria in Iraq. The screening of refugees revealed a low coverage rate for diphtheria, especially in children, probably due to deterioration of the health service infrastructure or intermittent basic health care in the country of provenience. In terms of public health measures, there is the need of administering booster doses to all refugees coming into Italy and into other host countries to increase the coverage rate against diphtheria. The implementation of the immunization programs against diphtheria in the countries of provenience is also strongly recommended.

Enterovirus surveillance of Italian healthy children

Surveillance of acute flaccid paralysis (AFP) is the golden strategy recommended by the WHO to verify the condition of polio eradication in a country. Because of the difficulty to detect all of the expected AFP cases and to reach the target incidence of 1/100,000 requested by WHO, the surveillance of enteroviruses in the population has been adopted by several countries as an important additional method to verify the absence of wild-poliovirus circulation. To complete the results of AFP surveillance set up in Italy in 1996, we have conducted a wild poliovirus surveillance by examining stool samples from 1551 healthy children aged less than 5 years, collected during the period January 1997 to January 1998. The children were from three cities (Parma, Rome and Bari) located in northern, central and southern Italy. Thirty-nine polioviruses, 72 non-polio enteroviruses and 50 enteric, nonentero (NE), viruses were isolated from stool specimens. Polioviruses identified were nine type 1, seven type 2 and twenty-three type 3. Characterization of isolates by both antigenic and molecular methods showed that all polioviruses were of vaccine origin. As expected, most polioviruses, especially types 2 and 3, presented retromutations known to be associated with loss of the Sabin attenuated phenotype. The results of this study support the data obtained from the active AFP surveillance conducted in Italy in the same period--on the absence of paralytic disease due to wild poliovirus--and altogether demonstrate the effectiveness of the vaccination program.

Molecular epidemiology and evolution of coxsackievirus A9

Genetic relationships between 35 clinical isolates of coxsackievirus A9 (CAV9), collected during the last five decades from different geographical regions, were investigated by partial sequencing. Analysis of a 150 nucleotide sequence at the VP1/2A junction region identified 12 CAV9 genotypes. While most of the strains within each genotype showed geographical clustering, the analysis also provided evidence for long-range importation of virus strains. Phylogenetic analysis of a longer region around the VP1/2A junction (approximately 390 nucleotides) revealed that the designated genotypes actually represented phylogenetic lineages. The phylogenetic grouping pattern of the isolates in the analysis of the VP4/VP2 region was similar to that obtained in the VP1/2A region whereas analysis of the 3D region indicated a strikingly different grouping, which suggests that recombination events may occur in the region encoding the nonstructural proteins. Analysis of the deduced amino acid sequences of the VP1 polypeptide demonstrated that the RGD (arginine-glycine-aspartic acid) motif, implicated in the interaction of the virus with integrin, was fully conserved among the isolates.

Surveillance of acute flaccid paralysis in Italy: 1996-1997. AFP Study Group. Acute flaccid paralysis

The last case of poliomyelitis due to transmission of indigenous wild poliovirus occurred in Italy in 1982. To achieve the certification of the eradication of poliomyelitis in Italy, an active surveillance of acute flaccid paralysis (AFP) in the population aged less than 15 years was set up following the World Health Organization (WHO) guidelines. The survey started in 1996 with a pilot study involving 4 out of 21 regions, and was gradually extended to a national level in 1997. The two-year survey identified five patients with diagnosis of vaccine associated paralytic poliomyelitis (VAPP). Polioviruses type 2 and 3 Sabin-like were isolated and characterized in three of them. In the remaining two cases, samples were collected late after the onset of symptoms, and poliovirus could not be isolated. No wild polioviruses were detected during the survey. The rate of non-polio AFP found in Italy in 1997 was 0.61 cases per 100,000, which is lower than the level of 1.0 case per 100,000 considered as acceptable by the WHO. This was mainly due to the delay in organizing the hospital network and starting the active search of AFP cases in the largest and most densely populated regions. Therefore, the overall rate of AFP found in Italy underestimates the global effectiveness of the program, which however will be better evaluated in the next few years. This study is the first systematic attempt to determine the rate of AFP in Italy.

Molecular detection and typing of human picornaviruses

Picornaviruses include several important clinical pathogens which cause diseases varying from common cold to poliomyelitis and hepatitis. Introduction of RT-PCR methods for the detection of these viruses has significantly facilitated the diagnosis of picornavirus infections and elucidated their etiological role in clinical illnesses. Partial sequence analysis of the genomes has been used for typing of the viruses and in studies of molecular epidemiology of picornaviruses. These molecular approaches are likely to become the most predominant techniques for the diagnosis and epidemiological analysis, particularly in the enterovirus infections.

Genomic characterization of human and environmental polioviruses isolated in Albania

Between April and December 1996, a serious outbreak of poliomyelitis occurred in Albania; almost 140 subjects were involved, and the episode presented an unusually high mortality rate (12%). During the outbreak, water samples from the Lana River in Tirana, Albania, and stool samples from two cases of paralytic poliomyelitis were collected and analyzed for the presence of polioviruses. Six polioviruses were isolated from the environmental and human samples, according to standard methods. All the samples were characterized by partial genomic sequencing of 330 bases across the 5' untranslated region (5'-UTR) (nucleotide positions 200 to 530) and of 300 bases across the VP1 region (nucleotide positions 2474 to 2774). Comparison of these sequences with those present in data banks permitted the identification of environmental isolates Lana A and Lana B as, respectively, a Sabin-like type 2 poliovirus and an intertypic recombinant poliovirus (Sabin-like type 2/wild type 1), both bearing a G instead of an A at nucleotide position 481. The two other environmental polioviruses were similar to the isolates from the paralytic cases. They were characterized by a peculiar 5'-UTR and by a VP1 region showing 98% homology with the Albanian epidemic type 1 isolates reported by other authors. This study confirms the environmental circulation in Albania of recombinant poliovirus strains, likely sustained by a massive vaccination effort and by the presence in the environment of a type 1 poliovirus, as isolated from the Lana River in Tirana about 2 months before the first case of symptomatic acute flaccid paralysis was reported in this town.