Marycelin Baba
University of Maiduguri, Medical Laboratory Science, Faculty Member
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Research Interests: Epidemiology, Environmental Health, Developing Countries, Medicine, Disease Outbreaks, and 15 morePopulation, Humans, Endemic Diseases, Vaccination, Risk factors, Prevalence, Survival Rate, Risk Factors, Health Care Costs, Utilization review, Outbreak, Biochemistry and cell biology, Health Services Accessibility, Mass vaccination, and Medical biochemistry and metabolomics
We sequenced 109 type 2 Sabin-like poliovirus isolates that had been collected from acute flaccid paralysis patients or healthy children in Nigeria. Understanding the genetic makeup of these viruses may contribute to polio eradication... more
We sequenced 109 type 2 Sabin-like poliovirus isolates that had been collected from acute flaccid paralysis patients or healthy children in Nigeria. Understanding the genetic makeup of these viruses may contribute to polio eradication efforts.
(See the article by Neal et al., on pages 889–90.) Wild poliovirus has remained endemic in northern Nigeria because of low coverage achieved in the routine immunization program and in supplementary immunization activities (SIAs). An... more
(See the article by Neal et al., on pages 889–90.) Wild poliovirus has remained endemic in northern Nigeria because of low coverage achieved in the routine immunization program and in supplementary immunization activities (SIAs). An outbreak of infection involving 315 cases of type 2 circulating vaccine-derived poliovirus (cVDPV2;.1 % divergent from Sabin 2) occurred during July 2005–June 2010, a period when 23 of 34 SIAs used monovalent or bivalent oral poliovirus vaccine (OPV) lacking Sabin 2. In addition, 21 ‘‘pre-VDPV2’ ’ (0.5%–1.0 % divergent) cases occurred during this period. Both cVDPV and pre-VDPV cases were clinically indistinguishable from cases due to wild poliovirus. The monthly incidence of cases increased sharply in early 2009, as more children aged without trivalent OPV SIAs. Cumulative state incidence of pre-VDPV2/cVDPV2 was correlated with low childhood immunization against poliovirus type 2 assessed by various means. Strengthened routine immunization programs in countries with suboptimal coverage and balanced use of OPV formulations in SIAs are necessary to minimize risks of VDPV emergence and circulation. The cornerstone of the Global Polio Eradication Initiative is immunization of children with multiple doses of oral poliovirus vaccine (OPV), via both routine immunization (RI) and supplementary immunization activities (SIAs) [1]. The key advantages of OPV are ease of administration and efficient induction of mucosal immunity, thereby limiting poliovirus shedding and person-to-person transmission [2]. Through widespread implementation of this approach and with standardized
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Poor systematic surveillance for Yellow Fever virus (YFV) is primarily due to lack of affordable diagnostic facilities in resource‐constrained countries. This study aimed at providing evidence‐based information on immunity against Yellow... more
Poor systematic surveillance for Yellow Fever virus (YFV) is primarily due to lack of affordable diagnostic facilities in resource‐constrained countries. This study aimed at providing evidence‐based information on immunity against Yellow Fever with a view to assessing the possibility of the recent epidemics persisting in Nigeria. Six hundred patients with febrile illness seeking malaria test in selected hospitals were tested for YFV antibody using three serological assays: ELISA IgM, microneutralization test (MNT) and plaque reduction neutralization test (PRNT). The three assays commonly detected YFV antibody (Ab) in 1.7% patients, MNT: IgM in 8.3%, IgM: PRNT in 7.1%, and MNT: PRNT in 3.2%. Immunity against YF was significantly higher in Bauchi and Borno than Adamawa and children aged 0–9 years compared to 20–29 years. YFV neutralizing antibody (nAb) strongly correlated with the vaccination status of the patients. More unvaccinated patients had nAb compared with the vaccinated. Immunity against YF among treated patients with antibiotic and/or antimalaria before sample collection inversely correlated with the untreated. YVnAb among unvaccinated indicates natural infections. Acute YFV infections were mistaken for malaria and natural infections are ongoing. Individuals aged more than or equal to 20 years should be targeted during mass vaccination campaigns. With low population immunity, repetitive YF epidemics in Nigeria is not yet over. The current policy on Yellow Fever vaccination in Nigeria still leaves a large unimmunized population at the risk of epidemics. Sufficient mass vaccination in combination with National Programme on Immunization remains key to averting YF epidemics.
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Background: Human non-polio enteroviruses (NPEVs) have been associated with certain life-threatening disorders in children. However, there is paucity of NPEV infection data in most developing countries. This study determined the 3-year... more
Background: Human non-polio enteroviruses (NPEVs) have been associated with certain life-threatening disorders in children. However, there is paucity of NPEV infection data in most developing countries. This study determined the 3-year prevalence of non-polio enteroviruses (NPEVs) among children in some Northern States of Nigeria. Materials and Methods: Duplicate stool samples were collected from 27778 children ≤15 years. These samples were processed and analyzed for characteristic NPEVs cytopathic effects (CPE) on L20B and RD cell lines. Tests were considered positive if the duplicate samples produced distinct CPE on both cell lines. Results: Of the 27778 samples processed, 3991 (14.4%) NPEVs were isolated. Participants of the male gender (14.5%) within the age range of 0-5 years (14.7%) from Yobe state (15.3%) whose samples were received in the month of June (22.2%) and in the year 2015 (18.8%) had the highest prevalence of NPEVs. June had significant risk factors of NPEVs (p˂0.00...
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Background: Human non-polio enteroviruses (NPEVs) have been associated with certain life-threatening disorders in children. However, there is paucity of NPEV infection data in most developing countries. This study determined the 3-year... more
Background: Human non-polio enteroviruses (NPEVs) have been associated with certain life-threatening disorders in children. However, there is paucity of NPEV infection data in most developing countries. This study determined the 3-year prevalence of non-polio enteroviruses (NPEVs) among children in some Northern States of Nigeria. Materials and Methods: Duplicate stool samples were collected from 27778 children ≤15 years. These samples were processed and analyzed for characteristic NPEVs cytopathic effects (CPE) on L20B and RD cell lines. Tests were considered positive if the duplicate samples produced distinct CPE on both cell lines. Results: Of the 27778 samples processed, 3991 (14.4%) NPEVs were isolated. Participants of the male gender (14.5%) within the age range of 0-5 years (14.7%) from Yobe state (15.3%) whose samples were received in the month of June (22.2%) and in the year 2015 (18.8%) had the highest prevalence of NPEVs. June had significant risk factors of NPEVs (p˂0.00...
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We followed the dynamics of capsid amino acid replacement among 403 Nigerian outbreak isolates of type 2 circulating vaccine-derived poliovirus (cVDPV2) from 2005 through 2011. Four different functional domains were analyzed: 1)... more
We followed the dynamics of capsid amino acid replacement among 403 Nigerian outbreak isolates of type 2 circulating vaccine-derived poliovirus (cVDPV2) from 2005 through 2011. Four different functional domains were analyzed: 1) neutralizing antigenic (NAg) sites, 2) residues binding the poliovirus receptor (PVR), 3) VP1 residues 1-32, and 4) the capsid structural core. Amino acid replacements mapped to 37 of 43 positions across all 4 NAg sites; the most variable and polymorphic residues were in NAg sites 2 and 3b. The most divergent of the 120 NAg variants had no more than 5 replacements in all NAg sites, and were still neutralized at titers similar to those of Sabin 2. PVR-binding residues were less variable (25 different variants; 0-2 replacements/isolate; 30/44 invariant positions), with the most variable residues also forming parts of NAg sites 2 and 3a. Residues 1-32 of VP1 were highly variable (133 different variants; 0-6 replacements/isolate; 5/32 invariant positions), with ...
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Measles is of particular concern in Nigeria because of the high fatality rate, and high morbidity rate, particularly in young children. Measles and its complications are a common reason for hospitalization, indicating very low... more
Measles is of particular concern in Nigeria because of the high fatality rate, and high morbidity rate, particularly in young children. Measles and its complications are a common reason for hospitalization, indicating very low immunization coverage. This study was carried out to elucidate the contributing factors from attitudes, beliefs and practices of mothers towards measles and its vaccination. A cross-sectional survey was conducted in Konduga Local Government Area. One per cent of the 500 mothers interviewed believed that measles is prevented by immunization, 16% that it is contagious or due to an infectious agent, 26% that it is caused by evil spirits, witchcraft and heat, and 25% had never heard of measles immunization. Twenty-seven per cent said they did not believe immunization was effective and 4% were not allowed to go for immunization by their husbands. Of those mothers whose children had developed measles, only 31% had been treated in formal health facilities. These resu...
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Efficient implementation of the global eradication strategies consisting of Acute Flaccid Paralysis (AFP) surveillance and mass immunization campaigns led to interruption of indigenous wild poliovirus transmission in Cameroon in 1999.... more
Efficient implementation of the global eradication strategies consisting of Acute Flaccid Paralysis (AFP) surveillance and mass immunization campaigns led to interruption of indigenous wild poliovirus transmission in Cameroon in 1999. This study describes type 1 and type 3 wild poliovirus (WPV) importation, incidence, geographic distribution and control since the original interruption of transmission in Cameroon. Stool samples from AFP patients under the age of 15 years in Cameroon were collected nationwide and subjected to virus isolation on RD and L20B cell cultures. Resulting virus isolates were typed by intratypic differentiation (ITD) and analysis of the VP1 coding sequence of the viral genome. Surveillance data originating from Cameroon between 2000 and 2014 were considered for retrospective descriptive analyses. From 2003 to 2009, multiple WPV importation events from neighboring countries affected mainly in the northern regions of Cameroon but did not led to sustained local transmission. Throughout this period, 16 WPV1 and 5 WPV3 were detected and identified as members of multiple clusters within type-specific West Africa B genotypes (WEAF-B). In 2013-2014, a polio outbreak associated to a highly evolved ("orphan") WPV1 affected four southern regions of Cameroon. The appearance of highly evolved lineage of type 1 WPV suggests potential surveillance gap and underscore the need to maintain comprehensive polio immunization activities and sensitive surveillance systems in place as long as any country in the world remains endemic for WPV.
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Context: In spite of great advances observed in modern medicine, plants still make an important contribution to health care. Hence, there is need for unrelenting effort in the exploration of the health benefit of medicinal plants.... more
Context: In spite of great advances observed in modern medicine, plants still make an important contribution to health care. Hence, there is need for unrelenting effort in the exploration of the health benefit of medicinal plants. Purpose: This work was designed to determine the role of the volatile oil of Camellia sinensis on the extracellular protease, which is one of the major virulent factors in the pathogenesis of Shigella dysenteriae and its antibacterial effects on eight other enteric bacterial as compared with the antibiotics Finding: The total antimicrobial effect of the volatile oil (355.0 mm) was significantly higher (p<0.05) than the antibiotics tested (203.0 mm). The minimum inhibitory and bactericidal concentrations of the oils revealed Escherichia coli as the most sensitive. However, relatively higher concentrations of the oils is required to achieve similar sensitivity against Salmonella and Shigella species . The activity of the partially purified extracellular protease, which is one of the virulence factors of Shigella dysenteriae was inhibited by the oil from different parts of the plant especially the leaf. The activity of this enzyme increased steadily between pH 7.0 – 8.0 and 40 – 50 o C. Summary: The volatile oils possessed antimicrobial activity and showed both competitive and noncompetitive kinetic inhibition of the extracellular protease of Shigella dysenteriae. Implication: The inhibitory action of the oil on protease from Shigella dysenteriae suggests the possible mode of action. Volatile oil from Camellia sinensis, especially the leaf, may be an important source of antibiotic against these organisms particularly Shigella dysenteriae.
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In spite of great advances observed in modern medicine, plants still constitute a major source of medicine especially in developing countries. Hence, there is need for unrelenting effort in the exploration of the health benefit of... more
In spite of great advances observed in modern medicine, plants still constitute a major source of medicine especially in developing countries. Hence, there is need for unrelenting effort in the exploration of the health benefit of medicinal plants. This work was designed to determine the effect of the volatile oils of Camellia sinensis on the extracellular protease, which is one of the major virulent factors in the pathogenesis of Shigella dysenteriae and its antibacterial effects on eight other enteric bacterial as compared with the antibiotics. The average total growth inhibition of the volatile oils from the leaf, stem and root of Camellia sinensis (291.0±33.0 mm) was significantly higher (p>0.05) than the antibiotics tested (97.0±25.0 mm). The minimum inhibitory and bactericidal concentrations of the oils revealed Escherichia coli as the most sensitive organism. However, relatively higher concentrations of the oils are required to achieve similar sensitivity against Salmonella and Shigella species . The kinetics of partially purified extracellular protease, which is one of the adjuncts virulence factors of Shigella dysenteriae, was competitively (leaf and root) and noncompetitively (stem) inhibited by these oils from different parts of the plant. The activity of this enzyme increased steadily between pH 7.0 – 8.0 and 40 – 50 o C. The volatile oils possessed antimicrobial activity and showed both competitive and noncompetitive kinetic inhibition of the extracellular protease of Shigella dysenteriae. The inhibitory action of the oil on extracellular protease from Shigella dysenteriae suggests the possible mode of action. Volatile oil from Camellia sinensis, especially the leaf, may be an important source of antibiotic against these organisms particularly Shigella dysenteriae.
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To assess the dynamics of genetic reversion of live poliovirus vaccine in humans, we studied molecular evolution in Sabin-like poliovirus isolates from Nigerian acute flaccid paralysis cases obtained from routine surveillance. We employed... more
To assess the dynamics of genetic reversion of live poliovirus vaccine in humans, we studied molecular evolution in Sabin-like poliovirus isolates from Nigerian acute flaccid paralysis cases obtained from routine surveillance. We employed a novel modeling approach to infer substitution and recombination rates from whole-genome sequences and information about poliovirus infection dynamics and the individual vaccination history. We confirmed observations from a recent vaccine trial that VP1 substitution rates are increased for Sabin-like isolates relative to the rate for the wild type due to increased nonsynonymous substitution rates. We also inferred substitution rates for attenuating nucleotides and confirmed that reversion can occur in days to weeks after vaccination. We combine our observations for Sabin-like virus evolution with the molecular clock for VP1 of circulating wild-type strains to infer that the mean time from the initiating vaccine dose to the earliest detection of ci...
Research Interests: Biology, Nigeria, Medicine, Molecular Epidemiology, Biological Sciences, and 15 morePhylogeny, Humans, Child, Female, Male, Infant, Molecular Phylogenetics and Evolution, Poliomyelitis, Newborn Infant, Time Factors, Mutation Rate, Poliovirus, Child preschool, Sequence homology, and Medical and Health Sciences
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ABSTRACT: The goal of point-of-care testing is to provide fast, convenient, and easy-to-use diagnostic assays that shorten the turnaround time of intervention. Several diagnostic tests have already migrated from the centralized... more
ABSTRACT: The goal of point-of-care testing is to provide fast, convenient, and easy-to-use diagnostic assays that shorten the turnaround time of intervention. Several diagnostic tests have already migrated from the centralized laboratory to patients’ bedside, physician offices and domestic environments in more developed countries. However, the situation is dramatically different in countries of the developing world where lack of facilities and resources still results in diagnosis to be inferred mostly from the symptoms only. Reliable and rapid diagnosis is urgently needed particularly in case of viral diseases with the concrete risk of outbreaks going undetected in the early stages. In this article we will advocate the necessity to implement robust point-of-care testing for viral diseases to overcome the diagnostic gap of less developed countries.
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Research Interests: Nigeria, Medicine, Hepatitis C, HIV, Hepatitis B, and 15 moreHumans, Female, Male, Prevalence, Antibody, Adult, Blood Transfusion, Blood Donors, Hepatitis B virus, Sensitivity and Specificity, Cross Sectional Studies, Enzyme Linked Immunosorbent Assay, Hepacivirus, immunoglobulin M, and HIV infections
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Research Interests: Microbiology, Epidemiology, Gastroenterology, Southeast Asia, Medical Microbiology, and 14 moreMedicine, Hepatology, Refugees, Humans, Country of Origin, United States, Clinical Sciences, Prevalence, Time Factors, Virus infection, chronic hepatitis B, Confidence Interval, Medical biochemistry and metabolomics, and Hepatitis B surface antigen
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A novel picornavirus genome was sequenced, showing 42.6%, 35.2%, and 44.6% of deduced amino acid identities corresponding to the P1, P2, and P3 regions, respectively, of the Aichi virus. Divergent strains of this new virus, which we named... more
A novel picornavirus genome was sequenced, showing 42.6%, 35.2%, and 44.6% of deduced amino acid identities corresponding to the P1, P2, and P3 regions, respectively, of the Aichi virus. Divergent strains of this new virus, which we named salivirus, were detected in 18 stool samples from Nigeria, Tunisia, Nepal, and the United States. A statistical association was seen between virus shedding and unexplained cases of gastroenteritis in Nepal ( P = 0.0056). Viruses with approximately 90% nucleotide similarity, named klassevirus, were also recently reported in three cases of unexplained diarrhea from the United States and Australia and in sewage from Spain, reflecting a global distribution and supporting a pathogenic role for this new group of picornaviruses.
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39 40 Since 2005, a large poliomyelitis outbreak associated with type 2 circulating vaccine41 derived poliovirus (cVDPV2) has occurred in northern Nigeria, where immunization coverage 42 with trivalent oral poliovirus vaccine (tOPV) has... more
39 40 Since 2005, a large poliomyelitis outbreak associated with type 2 circulating vaccine41 derived poliovirus (cVDPV2) has occurred in northern Nigeria, where immunization coverage 42 with trivalent oral poliovirus vaccine (tOPV) has been low. Phylogenetic analysis of P1/capsid 43 region sequences of isolates from each of the 403 cases reported in 2005–2011 resolved the 44 outbreak into 23 independent VDPV2 emergences, at least seven of which established circulating 45 lineage groups. Virus from one emergence (lineage group 2005-8; 361 isolates) was estimated to 46 have circulated for over six years. The population of the major cVDPV2 lineage group expanded 47 rapidly in early 2009, fell sharply after two tOPV rounds in mid-2009, and gradually expanded 48 again through 2011. The two major determinants of attenuation of the Sabin 2 OPV strain (A481 49 in the 5′-untranslated region [5′-UTR] and VP1-Ile143) had been replaced in all VDPV2 isolates; 50 most A481 5′-UTR replacements oc...
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Simultaneous Hepatitis B (HBV) and hepatitis C (HCV) virus infections have always been rare, but the situation could occur after accidental needle-stick injury and blood transfusion in the past. Rapid diagnostic tests were used to screen... more
Simultaneous Hepatitis B (HBV) and hepatitis C (HCV) virus infections have always been rare, but the situation could occur after accidental needle-stick injury and blood transfusion in the past. Rapid diagnostic tests were used to screen for HBsAg and anti-HCV antibodies among sutdents’ of University of Maiduguri in Northern Nigeria. Of the 200 volunteers screened, 8(4.0%) and 9(4.5%) were positive for HCV and HBV respectively while 1(0.5%) were found to be coinfected with the viruses. The gender related prevalence of HCV was 2.6% in females and 4.9% in males while for HBsAg was 2.6% in females and 5.7% in males. Coinfection was 0% and 1.3%% for males and females respectively (p > 0.05). Age related prevalence for HCV was 2.7% and 5.7% among those aged 18 - 25 years and 26-45 years respectively and similarly 5.4 and 3.4% for HBsAg, respectively. Coinfection was 0% among those aged 18 - 25 years old and 1.1% among those that were 26-45 years old. There was no statistically signifi...
Expanded program on immunization is one of the strategic universally accepted method for the control of childhood diseases which include poliomyelitis. In Nigeria both monovalent and trivalent oral polio vaccines are routinely used.... more
Expanded program on immunization is one of the strategic universally accepted method for the control of childhood diseases which include poliomyelitis. In Nigeria both monovalent and trivalent oral polio vaccines are routinely used. Thirty-six OPV vaccines representing three different batches of the vaccines in three different levels of health care vaccination centres (federal, state and local government) were monitored and tested. The vaccines were tested using L20B which is mouse cell line genetically 155 engineered with human poliovirus receptors; (CD ). All the 36 samples were found to be potent with a 10 maximum titre of log (8.38) and a minimum titre of log (7.58). The minimum titre was observed only in a primary vaccination centre. In addition, thermal stability was obtained using 16 vials obtained from 10 different storage facilities, had titres which ranged from log 6.5 to 8.4. These values still fell within the 10 normal limits recommended by WHO as minimum accepted values...
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Group A rotaviruses (RVA) are the leading cause of acute gastroenteritis (AGE) in children worldwide and cause up to 455,000 deaths annually, mostly in developing countries. During 2013, 66 RVAs from children with AGE admitted to four... more
Group A rotaviruses (RVA) are the leading cause of acute gastroenteritis (AGE) in children worldwide and cause up to 455,000 deaths annually, mostly in developing countries. During 2013, 66 RVAs from children with AGE admitted to four Nigerian hospitals were investigated. The G3P[6], G1P[8] and G2P[4] genotypes predominated. The VP7 and/or VP4 genes of 18 G3P[6]/[8]/[4], six G2P[4], three G12P[8]/[4], and two G1P[8] RVA strains were sequenced. The G3P[6] strains belonged to lineage G3-III and were different from G3 strains widespread in Asia. Phylogenetic analysis revealed substantial sequence conservation, suggesting continuing evolution and genomic reassortment but no zoonotic RVA transmission from animals.
Research Interests: Microbiology, Medical Microbiology, Brazil, Nigeria, Ireland, and 26 moreDiarrhea, Biological Sciences, Phylogeny, Disease Outbreaks, Humans, Sequence alignment, Hospitalization, Female, Male, Gastroenteritis, Infant, Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis, Newborn Infant, Aged, Rotavirus, Genotype, Molecular Characterization, Medical virology, Public health systems and services research, Feces, Brazilian, Genetic variation, Base Sequence, Enzyme Linked Immunosorbent Assay, Molecular Sequence Data, and Acute Disease
Clinical symptoms of malaria and typhoid infections are virtually indistinguishable from those initially seen in many arbovirus infections. Here we describe arbovirus co-infection detected in 310 sera samples collected from febrile,... more
Clinical symptoms of malaria and typhoid infections are virtually indistinguishable from those initially seen in many arbovirus infections. Here we describe arbovirus co-infection detected in 310 sera samples collected from febrile, clinically suspected malaria/typhoid patients in Borno State, Nigeria. Tested initially for Plasmodium falciparum by microscopy and for Salmonella Typhi by Widal test, samples were subsequently tested for chikungunya (CHIKV), yellow fever (YFV), dengue (DENV) and West Nile viruses (WNV) by plaque reduction neutralization test. While 92% of patients tested positive for malaria, typhoid, an arbovirus infection, or a combination of one or more of these types of infections, less than 1% of the patients tested positive for malaria alone and only 3.9% tested positive for typhoid alone. Approximately half of the patients tested positive for infection with a single arbovirus (48%) regardless of the presence or absence of malaria or typhoid. Of those who showed ...
Research Interests: Nigeria, Adolescent, Humans, Child, Female, and 11 moreAnimals, Male, Coinfection, Young Adult, Infant, Typhoid Fever, Aged, Middle Aged, Adult, Fever, and Arboviruses
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The largest recorded outbreak of a circulating vaccine-derived poliovirus (cVDPV), detected in Nigeria, provides a unique opportunity to analyze the pathogenicity of the virus, the clinical severity of the disease, and the effectiveness... more
The largest recorded outbreak of a circulating vaccine-derived poliovirus (cVDPV), detected in Nigeria, provides a unique opportunity to analyze the pathogenicity of the virus, the clinical severity of the disease, and the effectiveness of control measures for cVDPVs as compared with wild-type poliovirus (WPV). We identified cases of acute flaccid paralysis associated with fecal excretion of type 2 cVDPV, type 1 WPV, or type 3 WPV reported in Nigeria through routine surveillance from January 1, 2005, through June 30, 2009. The clinical characteristics of these cases, the clinical attack rates for each virus, and the effectiveness of oral polio vaccines in preventing paralysis from each virus were compared. No significant differences were found in the clinical severity of paralysis among the 278 cases of type 2 cVDPV, the 2323 cases of type 1 WPV, and the 1059 cases of type 3 WPV. The estimated average annual clinical attack rates of type 1 WPV, type 2 cVDPV, and type 3 WPV per 100,000 susceptible children under 5 years of age were 6.8 (95% confidence interval [CI], 5.9 to 7.7), 2.7 (95% CI, 1.9 to 3.6), and 4.0 (95% CI, 3.4 to 4.7), respectively. The estimated effectiveness of trivalent oral polio vaccine against paralysis from type 2 cVDPV was 38% (95% CI, 15 to 54%) per dose, which was substantially higher than that against paralysis from type 1 WPV (13%; 95% CI, 8 to 18%), or type 3 WPV (20%; 95% CI, 12 to 26%). The more frequent use of serotype 1 and serotype 3 monovalent oral polio vaccines has resulted in improvements in vaccine-induced population immunity against these serotypes and in declines in immunity to type 2 cVDPV. The attack rate and severity of disease associated with the recent cVDPV identified in Nigeria are similar to those associated with WPV. International planning for the management of the risk of WPV, both before and after eradication, must include scenarios in which equally virulent and pathogenic cVDPVs could emerge.