Identification and control of a poliomyelitis outbreak in Xinjiang, China

Thirty Years of Experience of Acute Flaccid Paralysis Surveillance for Polio - China, 1993-2022

Introduction

Detecting poliovirus infections proves to be highly challenging due to their asymptomatic nature and infectious potential, highlighting the crucial importance of effective detection methods in the context of polio eradication efforts. In many countries, including China, the primary approach for identifying polio outbreaks has been through acute flaccid paralysis (AFP) surveillance. In this study, we conducted an evaluation spanning three decades (1993-2022) to assess the effectiveness of AFP surveillance in China.

Methods

Data on all AFP cases identified since 1993 and national-level AFP surveillance system quality indicators aligned with the World Health Organization (WHO) standards were collected for analysis. The quality indicators assess surveillance sensitivity, completeness, timeliness of detection notification, case investigation, and laboratory workup. Surveillance sensitivity is determined by the non-polio AFP (NPAFP) detection rate among children under 15 years of age.

Results

Between 1993 and 2022, a total of 150,779 AFP cases were identified and reported. Within this pool, surveillance identified 95 cases of wild poliovirus (WPV) and 24 cases due to vaccine-derived poliovirus. From 1995 onwards, the detection rate of NPAFP cases consistently adhered to the WHO and national standards of ≥1 case per 100,000, falling between 1.38 and 2.76. Starting in 1997, all timeliness indicators consistently achieved the criteria of 80%, apart from the consistency in meeting standards set for the rate of positive specimens sent to the national laboratory.

Conclusions

AFP surveillance has been instrumental in China's accomplishment of maintaining a polio-free status. The ongoing adherence to key performance indicators, ensuring sensitivity and prompt specimen collection, demonstrates that AFP surveillance is proficient in detecting poliovirus in China. As we move into the post-eradication phase, AFP surveillance remains crucial for the sustained absence of polioviruses in the long term.

Identification and genetic characterization of a recently identified enterovirus C116 in China

Enterovirus C116 (EV-C116) is a new member of the enterovirus C group which is closely associated with several infectious diseases. Although sporadic studies have detected EV-C116 in clinical samples worldwide, there is currently limited information available. In this study, two EV-C-positive fecal specimens were detected in apparently healthy children, which harbored low abundance, through meta-transcriptome sequencing. Based on the prototypes of several EV-Cs, two lineages were observed. Lineage 1 included many types that could not cause EV-like cytopathic effect in cell culture. Three genogroups of EV-C116 were divided in the maximum likelihood tree, and the two strains in this study (XZ2 and XZ113) formed two different lineages, suggesting that EV-C116 still diffuses worldwide. Obvious inter-type recombination events were observed in the XZ2 strain, with CVA22 identified as a minor donor. However, another strain (XZ113) underwent different recombination situations, highlighting the importance of recombination in the formation of EV-Cs biodiversity. The EV-C116 strains could propagate in rhabdomyosarcoma cell cultures at low titer; however, EV-like cytopathic effects were not observed. HEp-2, L20B, VERO, and 293T cell lines did not provide an appropriate environment for EV-C116 growth. These results challenge the traditional recognition of the uncultured nature of EV-C116 strains and explain the difficulty of clinical detection.

Epidemiological survey and genetic characterization of type 3 vaccine-derived poliovirus isolated from a patient with four doses of inactivated polio vaccine in Henan Province, China

BACKGROUND

Vaccine-derived poliovirus (VDPV) is a potential threat to polio eradication because they can reintroduce into the general population and cause paralytic polio outbreaks, a phenomenon that has recently emerged as a prominent public health concern at the end of global polio eradication. This study aimed to describe the epidemiology and genetic characteristics of the first VDPV identified from a patient with acute flaccid paralysis (AFP), with four doses of inactivated polio vaccine immunization in Henan Province, China in 2017.

METHODS

The patient was diagnosed with type 3 VDPV. Subsequently, a series of epidemiological approaches was implemented, including a retrospective search of AFP cases, rate of vaccination assessment, study of contacts, and supplementary immunization activities. Fecal samples were collected, viral isolation was performed, and the viral isolates were characterized using full-length genomic sequencing and bioinformatic analysis.

RESULTS

Phylogenetic analysis showed that the viral isolates from the patient were different from other reported genetic clusters of type 3 VDPV worldwide. They were identified as a Sabin 3/Sabin 1 recombinant VDPV with a crossover site in the P2 region. Nucleotide substitutions, including U → C (472) and C → U (2493), have been identified, both of which are frequently observed as reversion mutations in neurovirulent type 3 poliovirus. A unique aspect of this case is that the patient had been vaccinated with four doses of inactive polio vaccine, and the serum neutralizing antibody for Sabin types 1 and 3 were 1∶16 and 1∶512, respectively. Thus, the patient was speculated to have been infected with type 3 VDPV, and the virus continued to replicate and be excreted for at least 41 d.

CONCLUSIONS

The existence of this kind of virus in human population is a serious risk and poses a severe challenge in maintaining a polio-free status in China. To the best of our knowledge, this is the first report of VDPV identified in the Henan province of China. Our results highlight the importance of maintaining a high-level vaccination rate and highly sensitive AFP case surveillance system in intercepting VDPV transmission.

Effects of maternal antibodies in infants on the immunogenicity and safety of inactivated polio vaccine in infants

The presence of maternal poliovirus antibodies may interfere with the immune response to inactivated polio vaccine (IPV), and its influence on the safety of vaccination is not yet understood. A total of 1146 eligible infants were randomly assigned (1:1) to the IPV and Sabin IPV (SIPV) groups to compare and analyze the efficacy of the two vaccines in preventing poliovirus infection. We pooled the SIPV and IPV groups and reclassified them into the maternal poliovirus antibody-positive group (MAPG; ≥1: 8) and the maternal poliovirus antibody-negative group (MANG; <1: 8). We evaluated the impact of maternal poliovirus antibodies by comparing the geometric mean titer (GMT), seroconversion rate, and geometric mean increase (GMI) of types I-III poliovirus neutralizing antibodies post-vaccination, and incidence rates of adverse reactions following vaccination between the MAPG and MANG. Respective seroconversion rates in the MAPG and MANG were 94% and 100%, 79.27% and 100%, and 93.26% and 100% (all serotypes, P < .01) for types I-III poliovirus, respectively. The GMT of all types of poliovirus antibodies in the MAPG (1319.13, 219.91, 764.11, respectively) were significantly lower than those in the MANG (1584.92, 286.73, 899.59, respectively) (P < .05). The GMI in the MAPG was significantly lower than that in the MANG (P < .05). No statistically significant difference in the incidence of local and systemic adverse reactions was observed between the MAPG and MANG. Thus, the presence of maternal poliovirus antibodies does not affect the safety of IPV but can negatively impact the immune responses in infants after IPV vaccination.

Outbreaks of Circulating Vaccine-derived Poliovirus in the World Health Organization Western Pacific Region, 2000-2021

The World Health Organization Western Pacific Region (WPR) has maintained the polio-free status for more than two decades. At the global level, there were only 6 confirmed polio cases due to wild type 1 poliovirus in Pakistan, Afghanistan, and Malawi in 2021, therefore, the risk of the importation of wild poliovirus from the endemic countries to the WPR is considerably lower than ever before. On the other hand, the risk of polio outbreaks associated with circulating vaccine-derived polioviruses (cVDPVs) still cannot be ignored even in the WPR. Since late 2010s, cVDPV outbreaks in the WPR have appeared to be more extensive in frequency and magnitude. Moreover, the emergence of concomitant polio outbreaks of type 1 and type 2 cVDPVs in the Philippines and Malaysia during 2019-2020 has highlighted the remaining risk of cVDPV outbreaks in high-risk areas and/or communities in the WPR. The previous cVDPV outbreaks in the WPR have been rapidly and effectively controlled, however, the future risk of polio outbreaks associated with cVDPVs needs to be reconsidered and polio immunization and surveillance strategies should be updated accordingly.

The Molecular Evolution of Type 2 Vaccine-Derived Polioviruses in Individuals with Primary Immunodeficiency Diseases

The oral poliovirus vaccine (OPV), which prevents person-to-person transmission of poliovirus by inducing robust intestinal immunity, has been a crucial tool for global polio eradication. However, polio outbreaks, mainly caused by type 2 circulating vaccine-derived poliovirus (cVDPV2), are increasing worldwide. Meanwhile, immunodeficiency-associated vaccine-derived poliovirus (iVDPV) is considered another risk factor during the final stage of global polio eradication. Patients with primary immunodeficiency diseases are associated with higher risks for long-term iVDPV infections. Although a limited number of chronic iVDPV excretors were reported, the recent identification of a chronic type 2 iVDPV (iVDPV2) excretor in the Philippines highlights the potential risk of inapparent iVDPV infection for expanding cVDPV outbreaks. Further research on the genetic characterizations and molecular evolution of iVDPV2, based on comprehensive iVDPV surveillance, will be critical for elucidating the remaining risk of iVDPV2 during the post-OPV era.

The association between the density of vaccination workers and immunization coverage in Zhejiang province, East China

Background: We aimed to evaluate whether the density of vaccination workers was associated with the immunization coverage in Zhejiang province.Methods: The immunization coverage of measles-containing vaccine (MCV), the third dose of diphtheria, tetanus, and pertussis combined vaccine (DTP3), and the third dose of poliomyelitis vaccine (PV3) was selected as the dependent variables. Immunization coverage data of children aged 13-23 months were taken from the Zhejiang immunization information system (ZJIIS). The aggregate density of vaccination workers was an independent variable in one set of regressions, while the full-time and part-time vaccination workers were adopted separately in other sets.Results: The density of total vaccination workers was positively and significantly associated with the immunization coverage (MCV: AOR = 3.36; DTP3: AOR = 2.68; PV3: AOR = 2.37). However, when the effects of full-time vaccination workers and part-time vaccination workers were assessed separately, we only found that the density of full-time vaccination workers was positively and significantly associated with the immunization coverage (MCV: AOR = 5.59; DTP3: AOR = 4.13; PV3: AOR = 3.28). The proportion of migrant children < 7 years and Land area were found as negative and significant factors for immunization coverage.Conclusions: A higher density of vaccination workers could improve the availability of vaccination services and immunization coverage. We recommended that government or other non-government organization should, apart from vaccine-related assistance, focus their efforts on human resources for vaccination.

Implication of a High Risk for Type 2 Vaccine-Derived Poliovirus Emergence and Transmission After the Switch From Trivalent to Bivalent Oral Poliovirus Vaccine

BACKGROUND

China implemented the globally synchronized switch from trivalent oral poliovirus vaccine (tOPV) to bivalent OPV (bOPV) and introduced 1 dose of inactivated poliovirus vaccine on 1 May 2016. We assessed the impact of the switch on the immunity level against poliovirus, especially type 2.

METHODS

Children born between 2014 and 2017, who were brought to the hospitals in Urumqi city, Xinjiang Province in 2017, were enrolled and blood samples were collected to test for antibody titers against poliovirus. A comparison of seroprevalence between the children born before (preswitch group) and after the switch (postswitch group) was performed to assess the impact of the switch on the immunity level against polio.

RESULTS

A total of 172 subjects were enrolled. The overall seroprevalences were 98.8%, 79.1%, and 98.3% for types 1, 2, and 3, respectively. Seroprevalence for type 2 significantly decreased from 91.6% in the preswitch group to 67.4% in the postswitch group, but no statistically significant change was observed for both types 1 and 3.

CONCLUSIONS

The switch from tOPV to bOPV can provide high-level immunity against types 1 and 3 but not against type 2, indicating a high risk of type 2 vaccine-derived poliovirus emergence and transmission.

Temporal phylogeny and molecular characterization of echovirus 30 associated with aseptic meningitis outbreaks in China

BACKGROUND

An outbreak of aseptic meningitis occurred from June to August 2016, in Inner Mongolia Autonomous Region, China.

METHODS

To determine its epidemiological characteristics, etiologic agent, and possible origin, specimens were collected for virus isolation and identification, followed by molecular epidemiological analysis.

RESULTS

A total of 363 patients were clinically diagnosed from June 1st to August 31st 2016, and most cases (63.1%, n = 229) were identified between June 22nd and July 17th, with children aged 6 to 12 years constituting the highest percentage (68.9%, n = 250). All viral isolates from this study belonged to genotype C of echovirus 30 (E30), which dominated transmission in China. To date, two E30 transmission lineages have been identified in China, of which Lineage 2 was predominant. We observed fluctuant progress of E30 genetic diversity, with Lineage 2 contributing to increased genetic diversity after 2002, whereas Lineage 1 was significant for the genetic diversity of E30 before 2002.

CONCLUSIONS

We identified the epidemiological and etiological causes of an aseptic meningitis outbreak in Inner Mongolia in 2016, and found that Lineage 2 played an important role in recent outbreaks. Moreover, we found that Gansu province could play an important role in E30 spread and might be a possible origin site. Furthermore, Fujian, Shandong, Taiwan, and Zhejiang provinces also demonstrated significant involvement in E30 evolution and persistence over time in China.

Cross-neutralization Capacity of Immune Serum from Different Dosage of Sabin Inactivated Poliovirus Vaccine Immunization against Multiple Individual Polioviruses

Introduction: Sabin strain inactivated poliovirus vaccine (sIPV) developed by Sinovac Biotech Co., Ltd., has shown good safety and immunogenicity against parental strains among infants in several finished pre-licensure clinical trials.Areas covered: To further study the neutralizing capacity of investigational sIPV immune serum against Sabin, Salk and recently circulating poliovirus strains, neutralization assay against ten individual strains was performed on backup serum collected from 250 infant participants of the finished phase II clinical trial.Expert commentary:: The sIPV can generate good immunogenicity against Sabin, Salk and recently circulating poliovirus strains. Taking into account its lower containment requirements and financial costs compared with the conventional Salk strain inactivated poliovirus vaccine, sIPV is an affordable and practical option for polio eradication.

COVID-19 and Vaccination Campaigns as "Western Plots" in Pakistan: Government Policies, (Geo-)politics, Local Perceptions, and Beliefs

Vaccination encounters multiple context-specific challenges-socio-cultural, economic, and political-that substantially affect its uptake. Likewise, natural disasters and health emergencies considerably impact immunization endeavors, such as the coronaviurs 2019 (COVID-19) pandemic that has overwhelmed the entire world. It was already anticipated that the pandemic would severely affect Pakistan's vaccination programs due to interruptions in routine vaccination and the overstretching of healthcare systems. Consequently, there are anticipations of outbreaks of other vaccine-preventable diseases (VPDs). Yet empirical evidence is missing. Drawing on qualitative research, this article focuses on the impact of COVID-19 on routine vaccination programs in Pakistan. Our data come from a small village located in Pakistan's Sindh province where local people refused the routine polio vaccine that was stopped for a while, then resumed in July 2020. They suspected both the vaccine and COVID-19 to be a "Western plot." We argue that these perceptions and practices can be seen against the backdrop of economic, socio-cultural, and (geo)political forces, which are encoded in "societal memory." Not only is there a need to reverse the significant impacts of COVID-19 on routine vaccination by arranging supplementary immunization activities (SIAs), but also the government must deal with other pressing issues that affect the vaccination programs in the country.

Molecular Epidemiological, Serological, and Pathogenic Analysis of EV-B75 Associated With Acute Flaccid Paralysis Cases in Tibet, China

Enterovirus B75 (EV-B75) is a newly identified serotype of the enterovirus B species. To date, only 112 cases related to EV-B75 have been reported worldwide, and research on EV-B75 is still limited with only two full-length genome sequences available in GenBank. The present study reported seven EV-B75 sequences from a child with acute flaccid paralysis and six asymptomatic close contacts in Shigatse, Tibet. Phylogenetic analysis revealed that the Tibetan strain was possibly imported from neighboring India. Seroepidemiological analyses indicated that EV-B75 has not yet caused a large-scale epidemic in Tibet. Similarity plots and boot scanning analyses revealed frequent intertypic recombination in the non-structural region of all seven Tibet EV-B75 strains. All seven Tibetan strains were temperature-sensitive, suggesting their poor transmissibility in the environment. Overall, though the seven Tibetan strains did not cause large-scale infection, prevention and control of the novel enterovirus cannot be underestimated.

Analysis of Monitoring, Early Warning and Emergency Response System for New Major Infectious Diseases in China and Overseas

In recent years, the impact of new major infectious diseases on people's normal life is becoming more and more frequent, which has brought great impact on people's life safety and social economy, especially the corona virus disease 2019, which has been sweeping the globe. Public health and disease prevention and control systems in different countries have different performances in response to the pandemic, but they all have exposed many shortcomings. Countries around the world urgently need to improve the monitoring, early warning and emergency response systems for new major infectious diseases. As the outpost and main part of medical rescue, the hospital urgently needs to establish a set of scientifically advanced emergency response mechanism that is suitable for the business process of the medical system and unified standards in order to improve the response efficiency and quality of emergency treatment.

Seroprevalence of poliovirus antibodies before and after polio vaccine switch in 2012 and 2017 in Beijing

In 2000, China was declared polio-free. However, in 2018, wild poliovirus (WPV) was still endemic in two of its neighboring countries, making WPV importation and outbreak alarming possibilities. This study documents the seroprevalence of poliovirus antibodies before and after the polio vaccine switch in 2012 and 2017 in Beijing. Cross-sectional population-based serologic surveys were conducted in 2012 and 2017 in Beijing. The study subjects were selected from 10 different age groups (<1, 1-4, 5-9, 10-14, 15-19, 20-24, 25-29, 30-34, 35-39, and ≥40 y) using a multi-stage-stratified sampling method. Neutralizing antibody titers against poliovirus serotypes 1 (P1), 2 (P2), and 3 (P3) were assayed by World Health Organization standards. The seropositive rates (SR) and geometric mean titer (GMT) of the neutralizing antibodies were 91.71% and 1:130.26, respectively, for P1, 94.09% and 1:113.39, respectively, for P2, and 88.78% and 1:79.65, respectively, for P3 before the switch in 2012, and 87.78% and 1:108.93, respectively, for P1, and 81.67% and 1:70.56, respectively, for P3 after the switch in 2017, with a statistically significant difference for P1 and P3 between 2012 and 2017. The neutralizing antibodies for all poliovirus serotypes differed among different age and vaccination groups in both 2012 and 2017. After switching polio vaccines twice in 2014 and 2016, the P1 and P3 polio antibody levels were lower in 2017 than in 2012. The P2 antibody levels were determined from the first dose of IPV. The seroprevalence of poliovirus antibodies after adjustment of the immunization schedule of the polio vaccine on January 1, 2020, must be further monitored.

Immunogenicity of Oral Polio Vaccine and Salk Inactive Polio Vaccine Against Xinjiang Imported Type 1 Wild Poliovirus

BACKGROUND

An outbreak of an imported Type 1 wild poliovirus from Pakistan occurred in the Xinjiang Uygur Autonomous Region of China in 2011, although the local immunity status of the oral polio vaccine (OPV) was relatively satisfied.

METHODS

Neutralizing antibody titers against the Xinjiang strain and Sabin 1 strain were measured in 237 sera from 3 groups of fully OPV-vaccinated persons and 1 group of infants fully vaccinated with the inactive polio vaccine (IPV). Additionally, 17 sera collected from 1 Xinjiang poliomyelitis case and his 16 contacts were also tested. Genomic sequencing was conducted the Xinjiang strain.

RESULTS

The antibody titers against the Xinjiang strain in each of 237 sera were significantly lower than those against the Sabin 1 strain. Notably, 40.0% of children in Group 1 were seronegative against the Xinjiang strain, which indicated that they might play an important role in wild poliovirus transmission, although their antibody titers against the Sabin 1 strain varied between 1:8 and 1:512. Meanwhile, serological results of the Xinjiang poliomyelitis case and his contacts also provided evidence that a proportion of OPV-vaccinated children had indeed been involved in the transmission chain of the Xinjiang outbreak. Genomic sequencing indicated that the Xinjiang strain was greatly distinguishable from the Sabin 1 strain in neutralizing antigenic sites.

CONCLUSION

The lack of neutralizing antibodies against the Xinjiang strain in persons vaccinated by OPV may be associated with the transmission of Type 1 wild poliovirus in Xinjiang. Using Salk IPV along with OPV might be considered in a wild poliovirus outbreak response, especially in the countries which continued to have persistent wild poliovirus circulation.

A Large-Scale Outbreak of Echovirus 30 in Gansu Province of China in 2015 and Its Phylodynamic Characterization

Background

Echovirus 30 (E-30) has been investigated and reported worldwide and is closely associated with several infectious diseases, including encephalitis; myocarditis; and hand, foot, and mouth disease. Although many E-30 outbreaks associated with encephalitis have been reported around the world, it was not reported in northwest China until 2015.

Methods

The clinical samples, including the feces, serum, throat swabs, and cerebrospinal fluid, were collected for this study and were analyzed for diagnosis. E-30 was isolated and processed according to the standard procedures. The epidemiological and phylogenetic analysis were performed to indicate the characteristics of E-30 outbreaks and phylodynamics of E-30 in China.

Results

The E-30 outbreaks affected nine towns of Gansu Province in 2015, starting at a school of Nancha town and spreading to other towns within 1 month. The epidemiological features showed that children aged 6–15 years were more susceptible to E-30 infection. The genotypes B and C cocirculated in the world, whereas the latter dominated the circulation of E-30 in China. The genome sequences of this outbreak present 99.3–100% similarity among these strains, indicating a genetic-linked aggregate outbreak of E-30 in this study. Two larger genetic diversity expansions and three small fluctuations of E-30 were observed from 1987 to 2016 in China, which revealed the oscillating patterns of E-30 in China. In addition, the coastal provinces of China, such as Zhejiang, Fujian, and Shandong, were initially infected, followed by other parts of the country. The E-30 strains isolated from mainland of China may have originated from Taiwan of China in the last century.

Conclusion

The highly similar E-30 genomes in this outbreak showed an aggregate outbreak of E-30, with nine towns affected. Our results suggested that, although the genetic diversity of E-30 oscillates, the dominant lineages of E-30 in China has complex genetic transmission. The coastal provinces played an important role in E-30 spread, which implied further development of effective countermeasures. This study provides a further insight into the E-30 outbreak and transmission and illustrates the importance of valuable surveillance in the future.

Phylogenetic analysis and phenotypic characterisatics of two Tibet EV-C96 strains

BACKGROUND

Enterovirus C96 (EV-C96) is a newly named type of enterovirus belonging to species C, and the prototype strain (BAN00-10488) was firstly isolated in 2000 from a stool specimen of a patient with acute flaccid paralysis in Bangladesh. In this study, we report the genomic and phenotypic characteristics of two EV-C96 strains isolated from individuals from the Tibet Autonomous Region of China.

METHODS

Human rhabdomyosarcoma (RD), human laryngeal epidermoid carcinoma (HEp-2), and human cervical cancer (Hela) cells were infected with the Tibet EV-C96 strains, and enterovirus RNA in the cell culture was detected with a real time RT-PCR-based enterovirus screening method. The temperature sensitivity of Tibet EV-C96 strains were assayed on a monolayer of RD cells in 24-well plates. Full-length genome sequencing was performed by a 'primer-walking' strategy, and the evolutionary history of EV-C96 was studied by maximum likelihood analysis.

RESULTS

Strain 2005-T49 grew in all three kinds of cells, and it was not temperature sensitive. In contrast, none of the three cells produced CPE for strain 2012-94H. Phylogenetic analysis of the two Tibetan viruses, other EV-C96 strains, and EV-C prototypes showed that EV-C96 strains were grouped into three clusters (Cluster1-3) based on their VP1 sequences, which may represent three genotypes. Phylogenetic trees based on the P2 and P3 regions highlighted the difference between Chinese EV-C96 strains and the EV-C96 prototype strain BAN-10488. All Chinese strains formed a cluster separate from BAN-10488, which clustered with CV-A1/CV-A22/CV-A19.

CONCLUSIONS

There is genetic variability between EV-C96 strains which suggest that at least few genetic lineages co-exist and there has been some degree of circulation in different geographical regions for some time. Some recombination events must have occurred during EV-C96 evolution as EV-C96 isolates cluster with different EV-C prototype strains in phylogenetic trees in different genomic regions. However, recombination does not seem to have occurred frequently as EV-C96 isolates from different years and locations appear to cluster together in all genomic regions analysed. These findings expand the understanding of the characterization of EV-C96 and are meaningful for the surveillance of the virus.

Profile of polio-compatible cases in Nigeria, 2006-2016

Background

The tremendous progress made by Nigeria towards polio eradication has recently suffered a setback with the isolation of circulating vaccine-derived poliovirus (cVDPV) type 2 from environmental samples and confirmation of four wild poliovirus (WPV) cases from acute flaccid paralysis (AFP) cases, with dates of onset of paralysis in July and August 2016. All these viruses were confirmed from the security-challenged northeastern state of Borno. Polio-compatible cases exist in Nigeria, and they indicate surveillance failure. Surveillance, therefore, has to be strengthened for the country to achieve certification. The objective of this paper is to highlight the epidemiological profile and magnitude of polio-compatible cases in Nigeria during the reporting period, as well as immunization and surveillance response activities conducted to close immunity and surveillance gaps.

Methods

We conducted a retrospective review of AFP surveillance performance and polio-compatible cases in Nigeria between 2006 and 2016 from the AFP database at the World Health Organization Country Office. We also reviewed and compared key epidemiological features of polio-compatible cases with those of wild poliovirus cases during the reporting period.

Results

The non-polio AFP rate improved from 6.5 in 2006 to 19.5 in 2016. The corresponding figures for stool adequacy rates were 88 and 98%. The total number of polio-compatible cases reported during the reporting period was 888, with the highest number (194) of cases reported in 2006 and the least (24) in 2016. Clusters of polio-compatible cases were reported every year during the reporting period except in 2015. The highest number (65) of polio-compatible cases in clusters was reported in 2006. The key epidemiological features of polio-compatible and wild poliovirus cases were similar.

Conclusion

AFP surveillance performance has improved significantly during the reporting period. Surveillance gaps still existed as shown by the presence of orphan viruses and polio-compatible cases, and these gaps need to be identified and closed to achieve certification.

A review of documents prepared by international organizations about influenza pandemics, including the 2009 pandemic: a bibliometric analysis

Background

World Health Organization (WHO), the World Bank, UN System Influenza Coordination (UNSIC) and other international organizations released a series of documents to fight against the influenza pandemic. Those documents have great significance on guiding influenza pandemic preparedness and responses and providing a multilevel, multi-directional influenza pandemic prevention and control network for their member countries. This study focuses on the above-mentioned influenza pandemic preparedness guidelines with the aim of exploring the roles of the society, defining the relationship of different interventions and evaluating the planning on influenza pandemic preparedness.

Methods

Documents about pandemic influenza preparedness were retrieved from the official websites of the following three international organizations, World Health Organization (WHO), the World Bank, UN System Influenza Coordination (UNSIC) with the key words ‘pandemic’, ‘influenza’ and the Boolean combinations of these words as the retrieval strategy. Guidelines, research study and meeting reports were included in the study. The categories of the ministries/departments involved and their roles/responsibilities in pandemic influenza preparedness were summarized. Word frequency of selected vocabularies about pandemic influenza preventive measures were collected from the documents and the correlations between the word frequency of these measures were analyzed. Ochiai coefficient was employed to show the correlation between the word vocabularies.

Results

A total of 38 records on the topic of pandemic influenza preparedness were included. The responsibilities of the whole-of-society mentioned in the international organizations’ documents varied across the 2009 influenza pandemic period. Meanwhile, it had been emphasized that a comprehensive influenza prevention and control plan in every sector should be developed and evaluated. Because various measures were emphasized in the guidelines after 2009 pandemic influenza, the correlations between the word frequencies of the various influenza preventive measures became stronger after the pandemic influenza.

Conclusions

Responsibilities of ministries of education, ministries of energy, ministries of agriculture and animal health, ministries of communication and the business sector in the pandemic influenza preparedness were described more comprehensively in the international organizations’ documents in 2017. Better understanding the variations of the guidelines delivered by international organizations would be useful for the member countries to strengthen their influenza control network.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3286-3) contains supplementary material, which is available to authorized users.

Landscape of emerging and re-emerging infectious diseases in China: impact of ecology, climate, and behavior

For the past several decades, the infectious disease profile in China has been shifting with rapid developments in social and economic aspects, environment, quality of food, water, housing, and public health infrastructure. Notably, 5 notifiable infectious diseases have been almost eradicated, and the incidence of 18 additional notifiable infectious diseases has been significantly reduced. Unexpectedly, the incidence of over 10 notifiable infectious diseases, including HIV, brucellosis, syphilis, and dengue fever, has been increasing. Nevertheless, frequent infectious disease outbreaks/events have been reported almost every year, and imported infectious diseases have increased since 2015. New pathogens and over 100 new genotypes or serotypes of known pathogens have been identified. Some infectious diseases seem to be exacerbated by various factors, including rapid urbanization, large numbers of migrant workers, changes in climate, ecology, and policies, such as returning farmland to forests. This review summarizes the current experiences and lessons from China in managing emerging and re-emerging infectious diseases, especially the effects of ecology, climate, and behavior, which should have merits in helping other countries to control and prevent infectious diseases.

Models and analyses to understand threats to polio eradication

To achieve complete polio eradication, the live oral poliovirus vaccine (OPV) currently used must be phased out after the end of wild poliovirus transmission. However, poorly understood threats may arise when OPV use is stopped. To counter these threats, better models than those currently available are needed. Two articles recently published in BMC Medicine address these issues. Mercer et al. (BMC Med 15:180, 2017) developed a statistical model analysis of polio case data and characteristics of cases occurring in several districts in Pakistan to inform resource allocation decisions. Nevertheless, despite having the potential to accelerate the elimination of polio cases, their analyses are unlikely to advance our understanding OPV cessation threats. McCarthy et al. (BMC Med 15:175, 2017) explored one such threat, namely the emergence and transmission of serotype 2 circulating vaccine derived poliovirus (cVDPV2) after OPV2 cessation, and found that the risk of persistent spread of cVDPV2 to new areas increases rapidly 1-5 years after OPV2 cessation. Thus, recently developed models and analysis methods have the potential to guide the required steps to surpass these threats. 'Big data' scientists could help with this; however, datasets covering all eradication efforts should be made readily available.Please see related articles: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-017-0937-y and https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-017-0941-2 .

China's Silk Road and global health

In 2013, China proposed its Belt and Road Initiative to promote trade, infrastructure, and commercial associations with 65 countries in Asia, Africa, and Europe. This initiative contains important health components. Simultaneously, China launched an unprecedented overseas intervention against Ebola virus in west Africa, dispatching 1200 workers, including Chinese military personnel. The overseas development assistance provided by China has been increasing by 25% annually, reaching US$7 billion in 2013. Development assistance for health from China has particularly been used to develop infrastructure and provide medical supplies to Africa and Asia. China's contributions to multilateral organisations are increasing but are unlikely to bridge substantial gaps, if any, vacated by other donors; China is creating its own multilateral funds and banks and challenging the existing global architecture. These new investment vehicles are more aligned with the geography and type of support of the Belt and Road Initiative. Our analysis concludes that China's Belt and Road Initiative, Ebola response, development assistance for health, and new investment funds are complementary and reinforcing, with China shaping a unique global engagement impacting powerfully on the contours of global health.

Vaccine-derived poliovirus surveillance in China during 2001-2013: the potential challenge for maintaining polio free status

Background

The goal of polio eradication is to complete elimination and containment of all wild, vaccine-related and Sabin polioviruses. Vaccine-derived poliovirus (VDPV) surveillance in China from 2001–2013 is summarized in this report, which has important implications for the global polio eradication initiative.

Methods

Acute flaccid paralysis (AFP) cases and their contacts with VDPVs isolated from fecal specimens were identified in our AFP surveillance system or by field investigation. Epidemiological and laboratory information for these children were analyzed and the reasons for the VDPV outbreak was explored.

Results

VDPVs were isolated from a total of 49 children in more than two-thirds of Chinese provinces from 2001–2013, including 15 VDPV cases, 15 non-polio AFP cases and 19 contacts of AFP cases or healthy subjects. A total of 3 circulating VDPVs (cVDPVs) outbreaks were reported in China, resulting in 6 cVDPVs cases who had not been vaccinated with oral attenuated poliomyelitis vaccine. Among the 4 immunodeficiency-associated VDPVs (iVDPVs) cases, the longest duration of virus excretion was about 20 months. In addition, one imported VDPV case from Myanmar was detected in Yunnan Province.

Conclusions

Until all wild, vaccine-related and Sabin polioviruses are eradicated in the world, high quality routine immunization and sensitive AFP surveillance should be maintained, focusing efforts on underserved populations in high risk areas.

The Global Polio Laboratory Network as a Platform for the Viral Vaccine-Preventable and Emerging Diseases Laboratory Networks

The Global Polio Laboratory Network (GPLN) began building in the late 1980s on a 3-tiered structure of 146 laboratories with different and complementary technical and support capacities (poliovirus isolation, molecular strain characterization including sequencing, quality assurance, and research). The purpose of this network is to provide timely and accurate laboratory results to the Global Polio Eradication Initiative. Deeply integrated with field case-based surveillance, it ultimately provides molecular epidemiological data from polioviruses used to inform programmatic and immunization activities. This network of global coverage requires substantial investments in laboratory infrastructure, equipment, supplies, reagents, quality assurance, staffing and training, often in resource-limited settings. The GPLN has not only developed country capacities, but it also serves as a model to other global laboratory networks for vaccine-preventable diseases that will endure after the polio eradication goal is achieved. Leveraging lessons learned during past 27 years, the authors discuss options for transitioning GPLN assets to support control of other viral vaccine-preventable, emerging, and reemerging diseases.

Implementing the communication for development strategy to improve knowledge and coverage of measles vaccination in western Chinese immunization programs: a before-and-after evaluation

Background

Communication for Development (C4D) is a strategy promoted by the United Nations Children’s Fund to foster positive and measurable changes at the individual, family, community, social, and policy levels of society. In western China, C4D activities have previously been conducted as part of province-level immunization programs. In this study, we evaluated the association of C4D with changes in parental knowledge of immunization services, measles disease, and measles vaccine, and changes in their children’s measles vaccine coverage.

Methods

From April 2013 to April 2014, C4D activities were implemented as part of provincial immunization programs in the Inner Mongolia, Guangxi, Chongqing, Guizhou, Tibet, Shaanxi, Gansu, Ningxia, and Qinghai provinces. We used a before-and-after study design and employed face-to-face interviews to assess changes in parental knowledge and vaccination coverage.

Results

We surveyed 2 107 households at baseline and 2 070 households after 1 year of C4D activities. Following C4D, 95% of caregivers were aware of the vaccination record check requirement for entry into kindergarten and primary school; 80% of caregivers were aware that migrant children were eligible for free vaccination; more than 70% of caregivers knew that measles is a respiratory infectious disease; and 90% of caregivers knew the symptoms of measles. Caregivers’ willingness to take their children to the clinic for vaccination increased from 51.3% at baseline to 67.4% in the post-C4D survey. Coverage of one-dose measles-containing vaccine (MCV) increased from 83.8% at baseline to 90.1% after C4D. One-dose MCV coverage was greater than 95% in the Guangxi, Shaanxi, and Gansu provinces. Two-dose MCV coverage increased from 68.5 to 77.6%. House-to-house communication was the most popular C4D activity among caregivers (91.6% favoring), followed by posters and educational talks (64.8 and 49.9% favoring).

Conclusions

C4D is associated with increased caregiver knowledge about measles, increased willingness to seek immunization services for their children, and increased measles vaccination coverage. Tailored communication strategies based on insights gained from these analyses may be able to increase vaccination coverage in hard-to-reach areas. C4D should be considered for larger scale implementation in China.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-017-0261-y) contains supplementary material, which is available to authorized users.

Lessons learnt to keep Europe polio-free: a review of outbreaks in the European Union, European Economic Area, and candidate countries, 1973 to 2013

Between 1973 and 2013, 12 outbreaks of paralytic poliomyelitis with a cumulative total of 660 cases were reported in the European Union, European Economic Area and candidate countries. Outbreaks lasted seven to 90 weeks (median: 24 weeks) and were identified through the diagnosis of cases of acute flaccid paralysis, for which infection with wild poliovirus was subsequently identified. In two countries, environmental surveillance was in place before the outbreaks, but did not detect any wild strain before the occurrence of clinical cases. This surveillance nonetheless provided useful information to monitor the outbreaks and their geographical spread. Outbreaks were predominantly caused by poliovirus type 1 and typically involved unvaccinated or inadequately vaccinated groups within highly immunised communities. Oral polio vaccine was primarily used to respond to the outbreaks with catch-up campaigns implemented either nationwide or in restricted geographical areas or age groups. The introduction of supplementary immunisation contained the outbreaks. In 2002, the European region of the World Health Organization was declared polio-free and it has maintained this status since. However, as long as there are non-vaccinated or under-vaccinated groups in European countries and poliomyelitis is not eradicated, countries remain continuously at risk of reintroduction and establishment of the virus. Continued efforts to reach these groups are needed in order to ensure a uniform and high vaccination coverage.

Safety, immunogenicity and persistence of immune response to the combined diphtheria, tetanus, acellular pertussis, poliovirus and Haemophilus influenzae type b conjugate vaccine (DTPa-IPV/Hib) administered in Chinese infants

We conducted 3 phase III, randomized, open-label, clinical trials assessing the safety, reactogenicity (all studies), immunogenicity (Primary vaccination study) and persistence of immune responses (Booster study) to the combined diphtheria, tetanus, pertussis, poliomyelitis, and Haemophilus influenzae type b vaccine (DTPa-IPV/Hib) in Chinese infants and toddlers.

In the Pilot study (NCT00964028), 50 infants (randomized 1:1) received 3 doses of DTPa-IPV/Hib at 2–3–4 (Group A) or 3–4–5 months of age (Group B). In the Primary study (NCT01086423), 984 healthy infants (randomized 1:1:1) received 3 doses of DTPa-IPV/Hib at 2–3–4 (Group A) or 3–4–5 (Group B) months of age, or concomitant DTPa/Hib and poliomyelitis (IPV) vaccination at 2–3–4 months of age (Control group); 825 infants received a booster dose of DTPa/Hib and IPV at 18–24 months of age (Booster study; NCT01449812).

In the Pilot study, unsolicited symptoms were more frequent in Group A (16 versus 1 infant; mostly upper respiratory tract infection and pyrexia); this observation was attributed to an epidemic outbreak of viral infections. Non-inferiority of 3-dose primary vaccination with DTPa-IPV/Hib over separately administered DTPa/Hib and IPV was demonstrated for Group A (primary objective). Similar antibody concentrations were observed in all groups, except for anti-polyribosyl-ribitol phosphate and anti-poliovirus types 1–3 which were higher in DTPa-IPV/Hib recipients. Protective antibody levels against all vaccine antigens remained high until booster vaccination. Three-dose vaccination with DTPa-IPV/Hib had a clinically acceptable safety profile.

Circulation of multiple serotypes of highly divergent enterovirus C in the Xinjiang Uighur Autonomous Region of China

Poliomyelitis associated with circulating vaccine-derived polioviruses (cVDPVs) is a serious public health issue in the post-eradication era, and the occurrence of recombinant cVDPVs emphasizes the need to elucidate enterovirus C (EV-C) epidemiology. Stool samples were collected from 826 healthy children in Southern Xinjiang in 2011 to investigate EV-C circulation and epidemiology. Thirty-six EV-Cs were isolated and assigned to eight EV-C serotypes by molecular serotyping, suggesting the circulation of diverse EV-Cs in Xinjiang. Phylogenetic analysis showed that the Xinjiang EV-C strains had larger variation compared to the prototype and other modern strains. Additionally, the results showed unique characteristics of Xinjiang EV-Cs, such as the cytopathicity of CV-A1 strains to RD cells; the high divergence in CV-A11, CV-A13, CV-A17, and CV-A20 strains; the divergence of Xinjiang CV-A24 from AHC-related CV-A24 variant stains distributed worldwide; and the circulation of two novel EV-C serotypes (EV-C96 and EV-C99). Evaluations of this dense and diverse EV-C ecosystem will help elucidate the processes shaping enteroviral biodiversity. This study will improve our understanding of the evolution of enteroviruses and the recombination potential between polioviruses and other EV-Cs.

Resurgence of Vaccine-Preventable Diseases in the United States: Anesthetic and Critical Care Implications

Vaccine-preventable diseases (VPDs) such as measles and pertussis are becoming more common in the United States. This disturbing trend is driven by several factors, including the antivaccination movement, waning efficacy of certain vaccines, pathogen adaptation, and travel of individuals to and from areas where disease is endemic. The anesthesia-related manifestations of many VPDs involve airway complications, cardiovascular and respiratory compromise, and unusual neurologic and neuromuscular symptoms. In this article, we will review the presentation and management of 9 VPDs most relevant to anesthesiologists, intensivists, and other hospital-based clinicians: measles, mumps, rubella, pertussis, diphtheria, influenza, meningococcal disease, varicella, and poliomyelitis. Because many of the pathogens causing these diseases are spread by respiratory droplets and aerosols, appropriate transmission precautions, personal protective equipment, and immunizations necessary to protect clinicians and prevent nosocomial outbreaks are described.

Immunogenicity of Two Different Sequential Schedules of Inactivated Polio Vaccine Followed by Oral Polio Vaccine Versus Oral Polio Vaccine Alone in Healthy Infants in China

BACKGROUND

Two vaccination schedules where inactivated polio vaccine (IPV) was followed by oral polio vaccine (OPV) were compared to an OPV-only schedule.

METHODS

Healthy Chinese infants received a 3-dose primary series of IPV-OPV-OPV (Group A), IPV-IPV-OPV (Group B), or OPV-OPV-OPV (Group C) at 2, 3, and 4 months of age. At pre-Dose 1, 1-month, and 14-months post-Dose 3, polio 1, 2, and 3 antibody titers were assessed by virus-neutralizing antibody assay with Sabin or wild-type strains. Adverse events were monitored.

RESULTS

Anti-polio 1, 2, and 3 titers were ≥8 (1/dil) in >99% of participants, and Group A and Group B were noninferior to Group C at 1-month post-Dose 3 as assessed by Sabin strain-based assay (SSBA). In Group A 1-month post-Dose 3, there was no geometric mean antibody titers (GMT) differences for types 1 and 3; type 2 GMTs were ≈3-fold higher by wild-type strain-based assay (WTBA) versus SSBA. For Group B, GMTs were ≈1.7- and 3.6-fold higher for types 1 and 2 via WTBA, while type 3 GMTs were similar. For Group C, GMTs were ≈6.3- and 2-fold higher for types 1 and 3 with SSBA, and type 2 GMTs were similar. Antibodies persisted in >96.6% of participants. Adverse event incidence in each group was similar.

CONCLUSIONS

A primary series of 1 or 2 IPV doses followed by 2 or 1 OPV doses was immunogenic and noninferior to an OPV-only arm. SSBA was better at detecting antibodies elicited by OPV with antibody titers correlated to the number of OPV doses (NCT01475539).

High-performance integrated virtual environment (HIVE): a robust infrastructure for next-generation sequence data analysis

The High-performance Integrated Virtual Environment (HIVE) is a distributed storage and compute environment designed primarily to handle next-generation sequencing (NGS) data. This multicomponent cloud infrastructure provides secure web access for authorized users to deposit, retrieve, annotate and compute on NGS data, and to analyse the outcomes using web interface visual environments appropriately built in collaboration with research and regulatory scientists and other end users. Unlike many massively parallel computing environments, HIVE uses a cloud control server which virtualizes services, not processes. It is both very robust and flexible due to the abstraction layer introduced between computational requests and operating system processes. The novel paradigm of moving computations to the data, instead of moving data to computational nodes, has proven to be significantly less taxing for both hardware and network infrastructure.

The honeycomb data model developed for HIVE integrates metadata into an object-oriented model. Its distinction from other object-oriented databases is in the additional implementation of a unified application program interface to search, view and manipulate data of all types. This model simplifies the introduction of new data types, thereby minimizing the need for database restructuring and streamlining the development of new integrated information systems. The honeycomb model employs a highly secure hierarchical access control and permission system, allowing determination of data access privileges in a finely granular manner without flooding the security subsystem with a multiplicity of rules. HIVE infrastructure will allow engineers and scientists to perform NGS analysis in a manner that is both efficient and secure. HIVE is actively supported in public and private domains, and project collaborations are welcomed.

Database URL: https://hive.biochemistry.gwu.edu

Household survey analysis of the impact of comprehensive strategies to improve the expanded programme on immunisation at the county level in western China, 2006-2010

OBJECTIVE

To evaluate interventions to improve routine vaccination coverage and caregiver knowledge in China's remote west, where routine immunisation is relatively weak.

DESIGN

Prospective pre-post (2006-2010) evaluation in project counties; retrospective comparison based on 2004 administrative data at baseline and surveyed post-intervention (2010) data in selected non-project counties.

SETTING

Four project counties and one non-project county in each of four provinces.

PARTICIPANTS

3390 children in project counties at baseline, and 3299 in project and 830 in non-project counties post-intervention; and 3279 caregivers at baseline, and 3389 in project and 830 in non-project counties post-intervention.

INTERVENTION

Multicomponent inexpensive knowledge-strengthening and service-strengthening and innovative, multisectoral engagement.

DATA COLLECTION

Standard 30-cluster household surveys of vaccine coverage and caregiver interviews pre-intervention and post-intervention in each project county. Similar surveys in one non-project county selected by local authorities in each province post-intervention. Administrative data on vaccination coverage in non-project counties at baseline.

PRIMARY OUTCOME MEASURES

Changes in vaccine coverage between baseline and project completion (2010); comparative caregiver knowledge in all counties in 2010.

ANALYSIS

Crude (χ(2)) analysis of changes and differences in vaccination coverage and related knowledge. Multiple logistic regression to assess associations with timely coverage.

RESULTS

Timely coverage of four routine vaccines increased by 21% (p<0.001) and hepatitis B (HepB) birth dose by 35% (p<0.001) over baseline in project counties. Comparison with non-project counties revealed secular improvement in most provinces, except new vaccine coverage was mostly higher in project counties. Ethnicity, province, birthplace, vaccination site, dual-parental out-migration and parental knowledge had significant associations with coverage. Knowledge increased for all variables but one in project counties (highest p<0.05) and was substantially higher than in non-project counties (p<0.01).

CONCLUSIONS

Comprehensive but inexpensive strategies improved vaccination coverage and caretaker knowledge in western China. Establishing multisectoral leadership, involving the education sector and including immunisation in public-sector performance standards, are affordable and effective interventions.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

A probable case of poliomyelitis imported to Malaysia

We report a previously well 10-month-old Somalian girl who acquired asymmetric lower limb weakness in July 2013 in Mogadishu, Banadir, before arriving in Malaysia at 12 months of age. In May 2013, there was a wild poliomyelitis outbreak in that area, as reported by the World Health Organization. Laboratory investigation, including cerebrospinal fluid, was unremarkable, and electrophysiological studies showed active axonal denervation in the left lower limb. The whole spine T2-weighted MRI revealed non-enhancing hyperintensities of the bilateral anterior horn cells, predominantly on the left side at T11-12. The viral isolations from two stool specimens at her presentation to our centre, 2 months after the onset of illness and 2 weeks apart, were negative. Despite lacking the acute virological evidence of poliomyelitis, in view of the girl's clinical, electrophysiological and classical spinal neuroradiological features, together with her temporal relationship with a World Health Organization reported wild poliomyelitis outbreak, we believe these findings are consistent with a diagnosis of imported poliomyelitis. A review at 30 months of age showed persistent left lower limb monoplegia with little recovery. Our patient reiterates the importance of maintaining awareness of wild polio importation, and keeping abreast of the latest news of global poliomyelitis outbreaks when treating patients with flaccid paralysis, even if they arrive from non-endemic poliomyelitis areas.

Polio in Pakistan: Social constraints and travel implications

The Global Polio Eradication Initiative (GPEI) in Pakistan has faced failure despite being implemented successfully. Polio cases were successfully reduced by 99% until 2005. However, thereafter, new polio cases were registered, which continue to rise annually. This repeat polio outbreak has placed the country on watch by the World Health Organization (WHO) due to travelers, and Hajj and Umrah pilgrims. The present report reviews the published literature for determining the social constraints to the polio eradication initiative in Pakistan. Religion, politics, awareness, insecurity, inequity, governance, and social responsibility have been identified as key social factors in the failure of any vaccination campaign. Possible interventions have been proposed, which include effectively using modern mass media and educating vaccinators on the social and cultural background of the target community.

A national cross-sectional study for poliovirus seroprevalence in the Republic of Korea in 2012: implication for deficiency in immunity to polio among middle-aged people

Background

A worldwide poliomyelitis eradication program was initiated in 1988; however, strains of wild poliovirus (WPV) are still endemic in some countries. Until WPV transmission is eradicated globally, importation and outbreaks of WPV are alarming possibilities. This study is the first report to document the polio immunity after 2004, when an inactivated polio vaccine (IPV) was introduced in the Republic of Korea.

Methods

A total of 745 serum samples from randomly selected patients ranging from 6 to 84 years of age were used for neutralization tests, performed in the World Health Organization polio national reference laboratory.

Results

Among the 745 tested sera, 439 (58.9%) were seropositive and 19 (2.6%) were seronegative to all PV serotypes. In all age groups, PV3 showed the lowest level of seroprevalence, at 509 cases (68.3%), compared to 616 (82.7%) for PV1 and 685 (91.9%) for PV2. In the 6–10-year age group, which included IPV-immunized children, the highest seropositive rate was observed and the difference in seroprevalence between PV3 and other serotypes was the lowest compared to the other age groups immunized with oral PV vaccines (OPV). In addition, the seronegative rates of all three PV types in children aged 6–10 in this study were found to be lower than those in OPV-immunized children reported in a previous study from the Republic of Korea. Meanwhile, middle-aged subjects (41–60 years) had the lowest seroprevalence and geometric mean titer.

Conclusions

This study indicates a deficiency in immunity to PV in middle-aged individuals, and low seroprevalence to PV3 in all age groups. In addition, due to the ongoing risk of importing PV, middle-aged people should consider PV vaccination before visiting a PV-endemic country. Our findings provide data to assist those involved in deciding future national polio vaccination strategies for the maintenance of a polio-free status in Korea.

The role of China in the global spread of the current cholera pandemic

Epidemics and pandemics of cholera, a severe diarrheal disease, have occurred since the early 19th century and waves of epidemic disease continue today. Cholera epidemics are caused by individual, genetically monomorphic lineages of Vibrio cholerae: the ongoing seventh pandemic, which has spread globally since 1961, is associated with lineage L2 of biotype El Tor. Previous genomic studies of the epidemiology of the seventh pandemic identified three successive sub-lineages within L2, designated waves 1 to 3, which spread globally from the Bay of Bengal on multiple occasions. However, these studies did not include samples from China, which also experienced multiple epidemics of cholera in recent decades. We sequenced the genomes of 71 strains isolated in China between 1961 and 2010, as well as eight from other sources, and compared them with 181 published genomes. The results indicated that outbreaks in China between 1960 and 1990 were associated with wave 1 whereas later outbreaks were associated with wave 2. However, the previously defined waves overlapped temporally, and are an inadequate representation of the shape of the global genealogy. We therefore suggest replacing them by a series of tightly delineated clades. Between 1960 and 1990 multiple such clades were imported into China, underwent further microevolution there and then spread to other countries. China was thus both a sink and source during the pandemic spread of V. cholerae, and needs to be included in reconstructions of the global patterns of spread of cholera.

Cholera is a life-threatening, diarrheal disease caused by the bacterium Vibrio cholerae. After a long interregnum of decades without epidemics, the seventh cholera pandemic spread globally since 1961, causing considerable morbidity and mortality. Our analysis of published and newly sequenced genomes provides details on genetic groupings within V. cholerae, so-called clades, that have developed during the recent pandemic spread of these bacteria, and, in some cases, persisted to modern times. We reconstructed some of the pathways taken by the current pandemic since its origins in Indonesia, and show that both South Asia and East Asia are important pathogenic reservoirs and sources of international transmissions.

The compatibility of inactivated-Enterovirus 71 vaccination with Coxsackievirus A16 and Poliovirus immunizations in humans and animals

Enterovirus 71 (EV71) is the key pathogen for Hand, Foot, and Mouth Disease (HFMD) and can result in severe neurological complications and death among young children. Three inactivated-EV71 vaccines have gone through phase III clinical trials and have demonstrated good safety and efficacy. These vaccines will benefit young children under the threat of severe HFMD. However, the potential immunization-related compatibility for different enterovirus vaccines remains unclear, making it hard to include the EV71 vaccine in Expanded Program on Immunization (EPI). Here, we measured the neutralizing antibodies (NTAbs) against EV71, Coxsackievirus A16 (CA16) and Poliovirus from infants enrolled in those EV71 vaccine clinical trials. The results indicated that the levels of NTAb GMTs for EV71 increased significantly in all 3 vaccine groups (high, middle and low dosages, respectively) post-vaccination. Seroconversion ratios and Geometric mean fold increase were significantly higher in the vaccine groups (≥ 7/9 and 8.9 ～ 228.1) than in the placebo group (≤ 1/10 and 0.8 ～ 1.7, P < 0.05). But no similar NTAb response trends were found in CA16 and 3 types of Poliovirus. The decrease of 3 types of Poliovirus NTAb GMTs and an increase of CA16 GMTs post-EV71-vaccination were found in vaccine and placebo groups. Further animal study on CA16 and poliovirus vaccine co-immunization or pre-immunization with EV71 vaccine in mice indicated that there was no NTAb cross-activity between EV71 and CA16/Poliovirus. Our research showed that inactivated-EV71 vaccine has good specific-neutralizing capacity and can be included in EPI.

Performance of acute flaccid paralysis surveillance compared with World Health Organization standards

AIM

To compare acute flaccid paralysis (AFP) surveillance systems used by members of the International Network of Paediatric Surveillance Units (INoPSU) across the five AFP surveillance performance indicators recommended by the World Health Organization (WHO) for the maintenance of polio-free certification.

METHODS

A survey was administered to AFP surveillance co-ordinators in five INoPSU member countries (Australia, Belgium, Canada, New Zealand and Switzerland). Data collected included information on surveillance system processes, WHO-recommended performance indicators, investigative practices and final diagnoses of cases from 2006 to 2010.

RESULTS

All countries contacted completed the survey. Each country used similar case definitions and processes for collecting AFP data. All countries used at least one of the WHO indicators for surveillance. No country consistently met the performance indicator for incidence or stool sampling. In all countries, at least one form of neurological testing was used to diagnose cases of AFP. Guillain-Barré syndrome was the most common final diagnosis in all countries for all years examined.

CONCLUSIONS

Industrialised countries surveyed do not consistently meet the WHO-recommended AFP surveillance performance indicators. An opportunity exists for INoPSU to suggest a standard way for member countries to collect AFP data in order to examine the potential for strengthening the current systems or introducing additional enterovirus surveillance or alternative/complementary neurological performance measures suitable for countries that have eliminated polio. INoPSU member countries are evaluating these possibilities.

An outbreak following importation of wild poliovirus in Xinjiang Uyghur Autonomous Region, China, 2011

Background

After more than 10 years without a case of wild poliovirus (WPV) in China, an outbreak occurred in 2011 in Xinjiang Uyghur Autonomous Region.

Methods

Acute flaccid paralysis (AFP) case surveillance was strengthened with epidemiological investigations and specimen collection and serological surveys were conducted among hospitalized patients.

Results

There were 21 WPV cases and 23 clinical compatible polio cases reported. WPV was isolated from 14 contacts of AFP cases and 13 in the healthy population. Incidence of WPV and clinical compatible polio cases were both highest among children <1 years, however, 24/44 (54.5%) polio cases were reported among adults aged 15–39 years.

Conclusions

High coverage of routine immunization should be maintained among children until WPV transmission is globally eradicated. Expansion of AFP case surveillance and use of serologic surveys to estimate population immunity should be conducted rapidly to guide preparedness and response planning for future WPV outbreaks.

Cross-border collaboration between China and Myanmar for emergency response to imported vaccine derived poliovirus case

Background

This report describes emergency response following an imported vaccine derived poliovirus (VDPV) case from Myanmar to Yunnan Province, China and the cross-border collaboration between China and Myanmar. Immediately after confirmation of the VDPV case, China disseminated related information to Myanmar with the assistance of the World Health Organization.

Methods

A series of epidemiological investigations were conducted, both in China and Myanmar, including retrospective searches of acute flaccid paralysis (AFP) cases, oral poliovirus vaccine (OPV) coverage assessment, and investigation of contacts and healthy children.

Results

All children <2 years of age had not been vaccinated in the village where the VDPV case had lived in the past 2 years. Moreover, most areas were not covered for routine immunization in this township due to vaccine shortages and lack of operational funds for the past 2 years.

Conclusions

Cross-border collaboration may have prevented a potential outbreak of VDPV in Myanmar. It is necessary to reinforce cross-border collaboration with neighboring countries in order to maximize the leverage of limited resources.

Factors contributing to outbreaks of wild poliovirus type 1 infection involving persons aged ≥15 years in the Democratic Republic of the Congo, 2010-2011, informed by a pre-outbreak poliovirus immunity assessment

BACKGROUND

The Democratic Republic of the Congo (DRC) experienced atypical outbreaks of wild poliovirus type 1 (WPV1) infection during 2010-2011 in that they affected persons aged ≥15 years in 4 (Bandundu, Bas Congo, Kasaï Occidental, and Kinshasa provinces) of the 6 provinces with outbreaks.

METHODS

Analyses of cases of WPV1 infection with onset during 2010-2011 by province, age, polio vaccination status, and sex were conducted. The prevalence of antibodies to poliovirus (PV) types 1, 2, and 3 was assessed in sera collected before the outbreaks from women attending antenatal clinics in 3 of the 4 above-mentioned provinces.

RESULTS

Of 193 cases of WPV1 infection during 2010-2011, 32 (17%) occurred in individuals aged ≥15 years. Of these 32 cases, 31 (97%) occurred in individuals aged 16-29 years; 9 (28%) were notified in Bandundu, 17 (53%) were notified in Kinshasa, and 22 (69%) had an unknown polio vaccination status. In the seroprevalence assessment, PV type 1 and 3 seroprevalence was lower among women aged 15-29 years in Bandundu and Kinshasa, compared with those in Kasaï Occidental. Seropositivity to PVs was associated with increasing age, more pregnancies, and a younger age at first pregnancy.

CONCLUSIONS

This spatiotemporal analysis strongly suggests that the 2010-2011 outbreaks of WPV1 infection affecting young adults were caused by a PV type 1 immunity gap in Kinshasa and Bandundu due to insufficient exposure to PV type 1 through natural infection or vaccination. Poliovirus immunity gaps in this age group likely persist in DRC.

An outbreak of type π vaccine-derived poliovirus in Sichuan province, China: emergence and circulation in an under-immunized population

BACKGROUND

During August 2011-February 2012, an outbreak of type Π circulating vaccine-derived poliovirus (cVDPVs) occurred in Sichuan Province, China.

METHODS

A field investigation of the outbreak was conducted to characterize outbreak isolates and to guide emergency response. Sequence analysis of poliovirus capsid protein VP1 was performed to determine the viral propagation, and a coverage survey was carried out for risk assessment.

RESULTS

One clinical compatible polio case and three VDPV cases were determined in Ngawa County, Ngawa Tibetan and Qiang Autonomous Prefecture, Sichuan Province. Case patients were unimmunized children, 0.8-1 years old. Genetic sequencing showed that the isolates diverged from the VP1 region of the type Π Sabin strain by 5-12 nucleotides (nt) and shared the same 5 nt VP1 substitutions, which indicate single lineage of cVDPVs. Of the 7 acute flaccid paralysis cases (all>6 months) reported in Ngawa Prefecture in 2011, 4 (57.1%) cases (including 2 polio cases) did not receive oral attenuated poliovirus vaccine. Supplementary immunization activities (SIAs) were conducted in February-May, 2012, and the strain has not been isolated since.

CONCLUSION

High coverage of routine immunization should be maintained among children until WPV transmission is globally eradicated. Risk assessments should be conducted regularly to pinpoint high risk areas or subpopulations, with SIAs developed if necessary.

Immunity to polio, measles and rubella in women of child-bearing age and estimated congenital rubella syndrome incidence, Cambodia, 2012

Significant gaps in immunity to polio, measles, and rubella may exist in adults in Cambodia and threaten vaccine-preventable disease (VPD) elimination and control goals, despite high childhood vaccination coverage. We conducted a nationwide serological survey during November-December 2012 of 2154 women aged 15-39 years to assess immunity to polio, measles, and rubella and to estimate congenital rubella syndrome (CRS) incidence. Measles and rubella antibodies were detected by IgG ELISA and polio antibodies by microneutralization testing. Age-structured catalytic models were fitted to rubella serological data to predict CRS cases. Overall, 29.8% of women lacked immunity to at least one poliovirus (PV); seroprevalence to PV1, PV2 and PV3 was 85.9%, 93.4% and 83.3%, respectively. Rubella and measles antibody seroprevalence was 73.3% and 95.9%, respectively. In the 15-19 years age group, 48.2% [95% confidence interval (CI) 42.4-54.1] were susceptible to either PV1 or PV3, and 40.3% (95% CI 33.0-47.5) to rubella virus. Based on rubella antibody seroprevalence, we estimate that >600 infants are born with CRS in Cambodia annually. Significant numbers of Cambodian women are still susceptible to polio and rubella, especially those aged 15-19 years, emphasizing the need to include adults in VPD surveillance and a potential role for vaccination strategies targeted at adults.