Intestinal antibody responses to a live oral poliovirus vaccine challenge among adults previously immunized with inactivated polio vaccine in Sweden.

BACKGROUND: Our understanding of the acquisition of intestinal mucosal immunity and the control of poliovirus replication and transmission in later life is still emerging. METHODS: As part of a 2011 randomised, blinded, placebo-controlled clinical trial of the experimental antiviral agent pocapavir (EudraCT 2011-004804-38), Swedish adults, aged 18-50 years, who had previously received four doses of inactivated polio vaccine (IPV) in childhood were challenged with a single dose of monovalent oral polio vaccine type 1 (mOPV1). Using faecal samples collected before and serially, over the course of 45 days, after mOPV1 challenge from a subset of placebo-arm participants who did not receive pocapavir (N=12), we investigated the kinetics of the intestinal antibody response to challenge virus by measuring poliovirus type 1-specific neutralising activity and IgA concentrations. RESULTS: In faecal samples collected prior to mOPV1 challenge, we found no evidence of pre-existing intestinal neutralising antibodies to any of the three poliovirus serotypes. Despite persistent high-titered vaccine virus shedding and rising serum neutralisation responses after mOPV1 challenge, intestinal poliovirus type 1-specific neutralisation remained low with a titer of ≤18.4 across all time points and individuals. Poliovirus types 1-specific, 2-specific and 3-specific IgA remained below the limit of detection for all specimens collected postchallenge. INTERPRETATION: In contrast to recent studies demonstrating brisk intestinal antibody responses to oral polio vaccine challenge in young children previously vaccinated with IPV, this investigation finds that adults previously vaccinated with IPV have only modest intestinal poliovirus type 1-specific neutralisation and no IgA responses that are measurable in stool samples following documented mOPV1 infection.

Polio and Measles Down the Drain: Environmental Enterovirus Surveillance in the Netherlands, 2005 to 2015.

Polioviruses (PVs) are members of the genus Enterovirus In the Netherlands, the exclusion of PV circulation is based on clinical enterovirus (EV) surveillance (CEVS) of EV-positive cases and routine environmental EV surveillance (EEVS) conducted on sewage samples collected in the region of the Netherlands where vaccination coverage is low due to religious reasons. We compared the EEVS data to those of the CEVS to gain insight into the relevance of EEVS for poliovirus and nonpolio enterovirus surveillance. Following the polio outbreak in Syria, EEVS was performed at the primary refugee center in Ter Apel in the Netherlands, and data were compared to those of CEVS and EEVS. Furthermore, we assessed the feasibility of poliovirus detection by EEVS using measles virus detection in sewage during a measles outbreak as a proxy. Two Sabin-like PVs were found in routine EEVS, 11 Sabin-like PVs were detected in the CEVS, and one Sabin-like PV was found in the Ter Apel sewage. We observed significant differences between the three programs regarding which EVs were found. In 6 sewage samples collected during the measles outbreak in 2013, measles virus RNA was detected in regions where measles cases were identified. In conclusion, we detected PVs, nonpolio EVs, and measles virus in sewage and showed that environmental surveillance is useful for poliovirus detection in the Netherlands, where live oral poliovirus vaccine is not used and communities with lower vaccination coverage exist. EEVS led to the detection of EV types not seen in the CEVS, showing that EEVS is complementary to CEVS.IMPORTANCE We show that environmental enterovirus surveillance complements clinical enterovirus surveillance for poliovirus detection, or exclusion, and for nonpolio enterovirus surveillance. Even in the presence of adequate surveillance, only a very limited number of Sabin-like poliovirus strains were detected in a 10-year period, and no signs of transmission of oral polio vaccine (OPV) strains were found in a country using exclusively inactivated polio vaccine (IPV). Measles viruses can be detected during an outbreak in sewage samples collected and concentrated following procedures used for environmental enterovirus surveillance.

Antiviral Activity of Pocapavir in a Randomized, Blinded, Placebo-Controlled Human Oral Poliovirus Vaccine Challenge Model.

BACKGROUND: Immunodeficient individuals who excrete vaccine-derived polioviruses threaten polio eradication. Antivirals address this threat. METHODS: In a randomized, blinded, placebo-controlled study, adults were challenged with monovalent oral poliovirus type 1 vaccine (mOPV1) and subsequently treated with capsid inhibitor pocapavir or placebo. The time to virus negativity in stool was determined. RESULTS: A total of 144 participants were enrolled; 98% became infected upon OPV challenge. Pocapavir-treated subjects (n = 93) cleared virus a median duration of 10 days after challenge, compared with 13 days for placebo recipients (n = 48; P = .0019). Fifty-two of 93 pocapavir-treated subjects (56%) cleared virus in 2-18 days with no evidence of drug resistance, while 41 of 93 (44%) treated subjects experienced infection with resistant virus while in the isolation facility, 3 (3%) of whom were infected at baseline, before treatment initiation. Resistant virus was also observed in 5 placebo recipients (10%). Excluding those with resistant virus, the median time to virus negativity was 5.5 days in pocapavir recipients, compared with 13 days in placebo recipients (P < .0001). There were no serious adverse events and no withdrawals from the study. CONCLUSIONS: Treatment with pocapavir was safe and significantly accelerated virus clearance. Emergence of resistant virus and transmission of virus were seen in the context of a clinical isolation facility. CLINICAL TRIALS REGISTRATION: EudraCT 2011-004804-38.

VIRO-TypeNed, systematic molecular surveillance of enteroviruses in the Netherlands between 2010 and 2014.

VIRO-TypeNed is a collaborative molecular surveillance platform facilitated through a web-based database. Genetic data in combination with epidemiological, clinical and patient data are shared between clinical and public health laboratories, as part of the surveillance underpinning poliovirus eradication. We analysed the combination of data submitted from 2010 to 2014 to understand circulation patterns of non-polio enteroviruses (NPEV) of public health relevance. Two epidemiological patterns were observed based on VIRO-TypeNed data and classical surveillance data dating back to 1996: (i) endemic cyclic, characterised by predictable upsurges/outbreaks every two to four years, and (ii) epidemic, where rare virus types caused upsurges/outbreaks. Genetic analysis suggests continuous temporal displacement of virus lineages due to the accumulation of (silent) genetic changes. Non-synonymous changes in the antigenic B/C loop suggest antigenic diversification, which may affect population susceptibility. Infections were frequently detected at an age under three months and at an older, parenting age (25-49 years) pointing to a distinct role of immunity in the circulation patterns. Upsurges were detected in the summer and winter which can promote increased transmissibility underlying new (cyclic) upsurges and requires close monitoring. The combination of data provide a better understanding of NPEV circulation required to control and curtail upsurges and outbreaks.

Antivirals against enteroviruses: a critical review from a public-health perspective.

The enteroviruses (EVs) of the Picornaviridae family are the most common viral pathogens known. Most EV infections are mild and self-limiting but manifestations can be severe in children and immunodeficient individuals. Antiviral development is actively pursued to benefit these high-risk patients and, given the alarming problem of antimicrobial drug resistance, antiviral drug resistance is a public-health concern. Picornavirus antivirals can be used off-label or as part of outbreak control measures. They may be used in the final stages of poliovirus eradication and to mitigate EV-A71 outbreaks. We review the potential emergence of drug-resistant strains and their impact on EV transmission and endemic circulation. We include non-picornavirus antivirals that inhibit EV replication, for example, ribavirin, a treatment for infection with HCV, and amantadine, a treatment for influenza A. They may have spurred resistance emergence in HCV or influenza A patients who are unknowingly coinfected with EV. The public-health challenge is always to find a balance between individual benefit and the long-term health of the larger population.

Intestinal immunity is a determinant of clearance of poliovirus after oral vaccination.

BACKGROUND: Response to challenge with live, attenuated, oral polio vaccine (OPV) is a measure of immunity induced by prior immunization. METHODS: Using stool samples from a study from Oman in which an initial schedule of inactivated polio vaccine (IPV) was followed by an OPV type 1 challenge, we quantitated virus shed, sequenced capsid proteins of recovered virus, and developed assays for neutralization of poliovirus and mucosal immunoglobulin A (IgA) detection. RESULTS: Neutralizing activity correlated with detection of polio-specific IgA in stool suspensions collected 7 days after OPV type 1 challenge. Both neutralization and IgA in stool were associated with cessation of virus shedding by day 7. Rapid development of an IgA response with cessation of shedding suggests that IPV primed for the early response to challenge. Correlation of neutralization activity and IgA detection provides evidence that polio-specific IgA intestinal antibody is a determinant of mucosal shedding/transmission and that IgA functions through neutralization of virus. In contrast, neither presence nor quantity of serum or intestinal antibody induced by IPV prior to challenge correlated with cessation of shedding. CONCLUSIONS: These assays provide an opportunity to study other immunization schedules to gain a broader understanding of the appearance and duration of a protective mucosal response to polio vaccination.

September through October 2010 multi-centre study in the Netherlands examining laboratory ability to detect enterovirus 68, an emerging respiratory pathogen.

During September and October 2010, the Dutch Public Health Institute detected an enterovirus (EV) 68 (EV68) epidemic in the Netherlands through general practitioner-based surveillance of acute respiratory infections. EV68 shares phenotypic and genotypic properties with human rhinovirus (HRV). Despite increased EV and HRV detections, Dutch clinical laboratories did not identify EV68. To assess the capability of Dutch clinical laboratories to detect EV68, ten laboratories with more than eight detected EV and HRV cases in September and October 2010 provided information about their detection algorithms and testing results for a 2010 Dutch EV68 strain. For EV detection mostly stool specimens (median 49%), respiratory specimens (median 27%) and cerebrospinal fluid (median 22%) were used. For HRV detection only respiratory specimens were used. Except for the Seeplex® RV15ACE EV-specific assay, all EV and 73% of HRV assays, including those of the Public Health Institute, were able to detect EV68. Two-step EV RT-PCR protocols were the most sensitive. Thus, laboratories might have misidentified EV68 as HRV. In addition, EV68 cases might have also been missed because patients with respiratory diseases are usually not tested for EV infection. Therefore, clinical laboratories should include EV detection in the differential diagnosis of patients presenting with respiratory symptoms.

Rapid and accurate identification of poliovirus strains used for vaccine production.

In the context of eradication of poliomyelitis the World Health Organization stimulates the development of inactivated polio vaccines based on attenuated virus strains. In addition to vaccine development, tests have to be designed to assess the vaccine quality. An important test is the identification test for poliovirus strains that are used for the vaccine production. A rapid and accurate PCR method with fluorescent probes has been developed to identify unequivocally the vaccine-specific poliovirus strains, such as Mahoney, MEF-1, Saukett H, Sabin type 1, Sabin type 2 and Sabin type 3.

Emergence and epidemic occurrence of enterovirus 68 respiratory infections in The Netherlands in 2010.

Following an increase in detection of enterovirus 68 (EV68) in community surveillance of respiratory infections in The Netherlands in 2010, epidemiological and virological analyses were performed to investigate the possible public health impact of EV68 infections. We retrospectively tested specimens collected from acute respiratory infections surveillance and through three children cohort studies conducted in The Netherlands from 1994 through 2010. A total of 71 of 13,310 (0.5%) specimens were positive for EV68, of which 67 (94%) were from symptomatic persons. Twenty-four (34%) of the EV68 positive specimens were collected during 2010. EV68-positive patients with respiratory symptoms showed significantly more dyspnea, cough and bronchitis than EV68-negative patients with respiratory symptoms. Phylogenetic analysis showed an increased VP1 gene diversity in 2010, suggesting that the increased number of EV68 detections in 2010 reflects a real epidemic. Clinical laboratories should consider enterovirus diagnostics in the differential diagnosis of patients presenting with respiratory symptoms.

Detection of recombination breakpoints in the genomes of human enterovirus 71 strains isolated in the Netherlands in epidemic and non-epidemic years, 1963-2010.

Evolutionary history of human enterovirus 71 (EV71) in the Netherlands shows displacement of virus subgenogroups, that only partly can be explained by antigenic changes. Additionally, occasional epidemics have occurred that remain to be explained. Previous studies have shown subgenogroup specific recombination events in the genome of Asian EV71 strains. To find clues on the role of genome recombination in evolution of the EV71 subgenogroups found in Europe and in the evolution of strains capable of causing outbreaks, we analyzed the genomes of 19 strains representing the genetic diversity of EV71 in the Netherlands between 1963 and 2010. We selected viruses from EV71 endemic and epidemic years (1986 and 2007). Subgenogroup specific genome recombination events were detected for subgenogroup B0, B1 and B2 viruses, in line with observed genome recombination events in Asian subgenogroup B3 and B4 viruses. Considering recombination events distinguishing strains from epidemic years from those of non-epidemic years, breakpoints for recombination were detected in the 5'UTR of B2 viruses from the outbreak in 1986, with highest similarity of the 5'UTR to B4 and B3 strains isolated during outbreaks in the Asian Pacific region. No indications for recombination were found in genogroup C isolates. Except for the '86 B2 isolates' Dutch isolates phylogenetically interspersed with international reference strains of the same subgenogroup, indicating a global dissemination of (recombinant) EV71 viruses. The difference observed in the 5'UTR of EV71 strains isolated in endemic versus epidemic years suggests that changes in the 5'UTR cause evolution of strains capable of causing outbreaks.

Metagenomic sequencing for virus identification in a public-health setting.

The use of metagenomics for virus discovery in clinical samples has opened new opportunities for understanding the aetiology of unexplained illness. This study explores the potential of this sequence-independent approach in a public-health setting, by systematic analysis of samples cultured from patients with unexplained illness through a combination of PCR-based assays and viral metagenomics. In total, 1834 cell-culture isolates were collected between 1994 and 2007 through the Enterovirus Surveillance programme in the Netherlands. During the 13 year period, seven samples that exhibited reproducible cytopathogenic effects in cell culture tested negative in standard PCR assays for a range of viruses. In order to fill the diagnostic gap, viral metagenomics was applied to these culture supernatants, resulting in the rapid identification of viruses in all of the samples. The unexplained samples contained BK polyomavirus, herpes simplex virus, Newcastle disease virus and the recently discovered Saffold viruses (SAFV) (which dominated the unexplained samples; n=4). The full genomic sequences of four SAFV genotype 3 (SAFV-3) viruses, which share 88-93 % nucleotide identity with known SAFV-3 viruses, are reported. Further screening for SAFV in additional cultured, unidentified clinical isolates from 2008 and 2009 resulted in identification of another SAFV-positive sample. Although the pathogenicity of the identified viruses has not been established, this study demonstrates that viral metagenomics is a powerful tool that can be integrated into public-health monitoring efforts to investigate unidentified viruses in cell cultures from clinical isolates where standard PCR assays fail to detect viruses.

Fractional doses of inactivated poliovirus vaccine in Oman.

BACKGROUND: We conducted a clinical trial of fractional doses of inactivated poliovirus vaccine administered to infants in Oman, in order to evaluate strategies for making the vaccine affordable for use in developing countries. METHODS: We compared fractional doses of inactivated poliovirus vaccine (0.1 ml, representing one fifth of a full dose) given intradermally with the use of a needle-free jet injector device, with full doses of vaccine given intramuscularly, with respect to immunogenicity and reactogenicity. Infants were randomly assigned at birth to receive either a fractional dose or a full dose of inactivated poliovirus vaccine at 2, 4, and 6 months. We also administered a challenge dose of monovalent type 1 oral poliovirus vaccine at 7 months and collected stool samples before and 7 days after administration of the challenge dose. RESULTS: A total of 400 infants were randomized, of whom 373 (93.2%) fulfilled the study requirements. No significant baseline differences between the groups were detected. Thirty days after completion of the three-dose schedule, the rates of seroconversion to types 1, 2, and 3 poliovirus were 97.3%, 95.7%, and 97.9%, respectively, in the fractional-dose group, as compared with 100% seroconversion to all serotypes in the full-dose group (P=0.01 for the comparison with respect to type 2 poliovirus; results with respect to types 1 and 3 poliovirus were not significant). The median titers were significantly lower in the fractional-dose group than in the full-dose group (P<0.001 for all three poliovirus serotypes). At 7 months, 74.8% of the infants in the fractional-dose group and 63.1% of those in full-dose group excreted type 1 poliovirus (P=0.03). Between birth and 7 months, 42 hospitalizations were reported, all related to infectious causes, anemia, or falls, with no significant difference between vaccination groups. CONCLUSIONS: These data show that fractional doses of inactivated poliovirus vaccine administered intradermally at 2, 4, and 6 months, as compared with full doses of inactivated poliovirus vaccine given intramuscularly on the same schedule, induce similar levels of seroconversion but significantly lower titers. (Current Controlled Trials number, ISRCTN17418767.)

Evolutionary trajectory of the VP1 gene of human enterovirus 71 genogroup B and C viruses.

From 1963 to 1986, human enterovirus 71 (HEV71) infections in the Netherlands were successively caused by viruses of subgenogroups B0, B1 and B2. A genogroup shift occurred in 1987, after which viruses of subgenogroups C1 and C2 were detected exclusively. This is in line with HEV71 typing in Australia, Europe and the USA, but is distinct from that in the Asian Pacific region, where HEV71 subgenogroups B3-B5 and C4-C5 have caused large outbreaks since 1997. To understand these observations in HEV71 epidemiology, the VP1-encoding regions of 199 HEV71 strains isolated in the Netherlands between 1963 and 2008 were used to study the detailed evolutionary trajectory and population dynamics of HEV71. Genogroup B viruses showed an epochal evolution, whereas genogroup C viruses evolved independently, which is in line with the co-circulation of C1 and C2 viruses in the Netherlands since 1997. Considering that strains from the Netherlands are interspersed phylogenetically with GenBank reference strains, the evolution of B1-B2, C1-C2 viruses has a global nature. Phylodynamic analysis confirmed that increased reporting of HEV71 infections in 1986 and 2007 reflected true epidemics of B2 and C2 viruses, respectively. Sequence analysis of the complete capsid region of a subset of isolates revealed several (sub)genogroup-specific residues. Subgenogroup B2-specific rabbit antiserum showed cross-neutralization of B0, B1 and B2 viruses, but not of subgenogroup C1 or C2 viruses, probably explaining the global shift to genogroup C in 1987 following a B2 epidemic. Anti-C1 rabbit serum neutralized both genogroup B and C viruses. Global herd immunity against C1 and C2 viruses possibly explains why epidemics with subgenogroups B4 and C4 are restricted to the Asian Pacific region.

Epidemiology of enterovirus 71 in the Netherlands, 1963 to 2008.

The incidence of enterovirus 71 (EV71) infection has greatly increased in the Asian Pacific region since 1997. Several large outbreaks, caused by different subgenogroups of EV71, occurred with high rates of morbidity and a substantial number of deaths. In 2007, 58 cases of EV71 infection requiring hospitalization were reported in The Netherlands after a period of low endemicity of 21 years. These events triggered a study on the epidemiology of EV71 in The Netherlands. Genetic analysis of the VP1 capsid region of 199 EV71 isolates collected from 1963 to 2008 as part of enterovirus surveillance activities revealed a change in the prevailing subgenogroups over time. From 1963 to 1986 infections were caused by three different and successive lineages belonging to subgenogroup B (the novel lineage designated B0, as well as B1 and B2). In 1987, following a major epidemic the previous year, the B genogroup was replaced by genogroup C strains of lineages C1 and, later, C2. Analyses of the clinical data suggested that there were differences between infection with genogroup B and with genogroup C strains in terms of the age groups affected and the severity of illness. From comparative analysis with genomic data available in the public domain, we concluded that EV71 strain evolution shows a global pattern, which leads to the question of whether the recently emerged C4 lineage strains will also spread outside of Asia.

Shedding of vaccine viruses with increased antigenic and genetic divergence after vaccination of newborns with monovalent type 1 oral poliovirus vaccine.

For the final stages in the eradication of poliovirus type 1 (P1), the World Health Organization advocates the selective use of monovalent type 1 oral poliovirus vaccine (mOPV1). To compare the immunogenicity of mOPV1 with that of trivalent OPV (tOPV) in infants, a study was performed in Egypt in 2005. Newborns were vaccinated with mOPV1 or tOPV immediately after birth and were challenged with mOPV1 after 1 month. Vaccination with mOPV1 at birth resulted in significantly higher seroconversion against P1 viruses and lower excretion of P1 viruses than vaccination with tOPV. Intratypic differentiation of the viruses shed by the newborns revealed the presence of remarkably high numbers of antigenically divergent (AD) P1 isolates, especially in the mOPV1 study group. The majority of these AD P1 isolates (71%) were mOPV1 challenge derived and were shed by newborns who did not seroconvert to P1 after the birth dose. Genetic characterization of the viruses revealed that amino acid 60 of the VP3 region was mutated in all AD P1 isolates. Isolates with substitution of residue 99 of the VP1 region had significantly higher numbers of nonsynonymous mutations in the VP1 region than isolates without this substitution and were preferentially shed in the mOPV1 study group. The widespread use of mOPV1 has proven to be a powerful tool for fighting poliovirus circulation in the remaining areas of endemicity. This study provides another justification for the need to achieve high vaccination coverage in order to prevent the circulation of AD strains.

Monovalent type 1 oral poliovirus vaccine in newborns.

BACKGROUND: In 1988, the World Health Assembly resolved to eradicate poliomyelitis. Although substantial progress toward this goal has been made, eradication remains elusive. In 2004, the World Health Organization called for the development of a potentially more immunogenic monovalent type 1 oral poliovirus vaccine. METHODS: We conducted a trial in Egypt to compare the immunogenicity of a newly licensed monovalent type 1 oral poliovirus vaccine with that of a trivalent oral poliovirus vaccine. Subjects were randomly assigned to receive one dose of monovalent type 1 oral poliovirus vaccine or trivalent oral poliovirus vaccine at birth. Thirty days after birth, a single challenge dose of monovalent type 1 oral poliovirus vaccine was administered in all subjects. Shedding of serotype 1 poliovirus was assessed through day 60. RESULTS: A total of 530 subjects were enrolled, and 421 fulfilled the study requirements. Thirty days after the study vaccines were administered, the rate of seroconversion to type 1 poliovirus was 55.4% in the monovalent-vaccine group, as compared with 32.1% in the trivalent-vaccine group (P<0.001). Among those with a high reciprocal titer of maternally derived antibodies against type 1 poliovirus (>64), 46.0% of the subjects in the monovalent-vaccine group underwent seroconversion, as compared with 21.3% in the trivalent-vaccine group (P<0.001). Seven days after administration of the challenge dose of monovalent type 1 vaccine, a significantly lower proportion of subjects in the monovalent-vaccine group than in the trivalent-vaccine group excreted type 1 poliovirus (25.9% vs. 41.5%, P=0.001). None of the serious adverse events reported were attributed to the trial interventions. CONCLUSIONS: When given at birth, monovalent type 1 oral poliovirus vaccine is superior to trivalent oral poliovirus vaccine in inducing humoral antibodies against type 1 poliovirus, overcoming high preexisting levels of maternally derived antibodies, and increasing the resistance to excretion of type 1 poliovirus after administration of a challenge dose. (Current Controlled Trials number, ISRCTN76316509.)

Prevalence of human parechovirus in the Netherlands in 2000 to 2007.

Infection with human parechovirus 3 (HPeV3) was described for the first time in Japan in 2004 and reportedly is more often associated with severe disease than infection with HPeV1 or HPeV2. In 2004, infections with HPeV3 were observed for the first time in The Netherlands. Genetic analysis showed several different lineages, suggesting endemic circulation. We analyzed 163 cell culture isolates from the same number of patients tested in routine virological laboratories as part of the national enterovirus surveillance program. Isolates were collected between 2000 and 2007 and could not be characterized by routine methods. In total, 155 isolates (95%) were found positive for HPeV by a reverse transcription-PCR assay targeting the 5' untranslated region, explaining the majority of the diagnostic deficit in enterovirus surveillance for these years. Typing of the isolates by use of partial genome sequencing of the VP1/2A region revealed the presence of 55 HPeV1, 2 HPeV2, 89 HPeV3, 1 HPeV4, and 8 HPeV5 isolates. We compared isolation dates, age groups affected, and clinical pictures, which were reported as part of the routine surveillance. Clear differences in epidemiology were observed, with HPeV3 occurring at intervals of 2 years and in the spring-summer season, whereas HPeV1 was observed in small numbers throughout each year, with a low in the summer months. HPeV3 infection affected younger children than HPeV1 infection and was significantly more often associated with fever, meningitis, and viremia.

Containment of polioviruses after eradication and OPV cessation: characterizing risks to improve management.

The goal of the World Health Organization is to stop routine use of oral poliovirus vaccine shortly after interruption of wild poliovirus transmission. A key component of this goal is to minimize the risk of reintroduction by destruction of polioviruses except in an absolute minimum number of facilities that serve essential functions and implement effective containment. Effective containment begins with a complete facility risk assessment. This article focuses on characterizing the risks of exposure to polioviruses from the essential vaccine production, quality control, and international reference and research facilities that remain. We consider the potential exposure pathways that might lead to a poliovirus reintroduction, including para-occupational exposures and releases to the environment, and review the literature to provide available estimates and a qualitative assessment of containment risks. Minimizing the risk of poliovirus transmission from a poliovirus facility to increasingly susceptible communities is a crucial and ongoing effort requiring understanding and actively managing the potential exposure pathways.

Syndromic surveillance in the Netherlands for the early detection of West Nile virus epidemics.

West Nile virus (WNV) is an arthropod-borne flavivirus that is endemic in Africa, Europe, and Eastern Asia. The recent introduction and rapid dissemination of the virus in the United States as well as an increase in WNV outbreaks in Europe, has raised concerns for its spread in Europe. A surveillance system was developed to allow timely detection of an introduction of WNV infections in The Netherlands. This program focuses on cases presenting with neurological disease and includes the monitoring of hospital discharge diagnoses, trends in cerebrospinal fluid (CSF) diagnostic requests, laboratory testing of CSF, and monitoring of neurological disease in horses. Retrospective data from the hospital discharge records showed yearly peaks of unexplained meningitis and (meningo)encephalitis in the summer. A total of 781 CSF samples from humans and 71 serum and/or CSF samples from horses presenting with neurological disease of suspected viral etiology tested negative for the presence of specific antibodies to WNV. With a coverage rate of 59% in 2003, the probability that a cluster of five WNV cases presenting with neurological symptoms would have been detected was 99%. We conclude that, from 1999 to 2004, no evidence of WNV infection could be found in either humans or horses in The Netherlands.

Risk of introduction of poliovirus into a Dutch Cape Verdian community during an outbreak of poliovirus in Cape Verde, 2000.

OBJECTIVE: To assess the risk of introduction of polio virus in a Cape Verdian community of Rotterdam, during the polio epidemic in Cape Verde in 2000. METHODS: All 225 insufficiently vaccinated 0-14-year-old Cape Verdian children (n=4188) and a random sample of 285 out of all 15-30-year-old Cape Verdians (n=5074) in Rotterdam were surveyed to assess travel behaviour and vaccination coverage. Faecal specimens were collected and sewage samples taken in neighbourhoods with a sizable Cape Verdian population for testing of polio virus. RESULTS: During the polio epidemic in Cape Verde, 10% of insufficiently vaccinated children aged 0-14 years and 17% of adults aged 15-30 years living in Rotterdam reported travelling to Cape Verde. 94.6% of Cape Verdians in Rotterdam aged 0-14 years were sufficiently vaccinated against polio, but 9 of 91 insufficiently vaccinated children had travelled to Cape Verde during the epidemic. Of those aged 15-30 years, 10% were not vaccinated against polio. In the faeces of 80 insufficiently vaccinated individuals aged 0-14 years and in 74 adults aged 15-30 years, no poliovirus was detected. Samples of sewage from six sites were negative for poliovirus. CONCLUSION: No evidence of poliovirus infection was found in the Cape Verde population in Rotterdam despite extensive travel to the Cape Verde during the outbreak.