Endemic Cholera Research Articles

Why the Endemoepidemicity Persistence of Cholera in Moba (DR. of Congo)? Preliminary Study in the Health Area of Regeza in 2016

Background: Cholera is a very old endemo-epidemic disease linked to the conditions of defective hygiene. It is a public health problem, mainly in Africa and Asia. Aim: The purpose of this preliminary study was to determine the level of knowledge of the population in relation to the factors favoring the endemicity and epidemicity of cholera among the exposed populations. Methods: This is a prospective, descriptive cross-sectional and analytical study. Interviewing and document analysis techniques were used in the different strata over the three-month period, from April to June 2016. Results: The profile of the respondents was mostly male (56.7%) aged over 30 years (61.2%), farmers (40.9%) or fishermen (26.1%) with a low level of instruction. The mean age was 32.1 ± 2.3 years with extremes ranking from 18 to 57 years. This study revealed that the main factors contributing to endemicity and epidemicity persistence of cholera were the low level of education, the environmental proximity with rivers and Lake Tanganyika, the incorrect habits of the population to think of the mystic in the genesis of cholera cases disease, low level of mobilization for cholera control, poor knowledge of the pathways of transmission of cholera, poor treatment of drinking water and the large consumption of inadequate water, knowledge of the critical moments of handwashing, the low use of soap or ash when washing hands, the large proportion of plots without latrines or with unhygienic latrines, poor management of household waste, poor organization of placement sessions at the level of cholera, poor knowledge of the means available to fight against cholera, poor management of faecal peril and poor general hygiene conditions. Conclusion: The conditions of poor knowledge of cholera and of deficient hygiene combined in our environment are favorable to the endemicity and sometimes the occurrence of cholera epidemics. Efforts should be made in relation to the improvement of hygiene conditions (individual and collective), communication for behavioral change and education of the population in the fight against cholera. The tree solution to the problems of cholera encountered in this study (in Appendix) may be the model to follow.

РАСПРОСТРАНЕННОСТЬ ICE ЭЛЕМЕНТОВ РАЗЛИЧНЫХ ТИПОВ У V. CHOLERAE

With the help of a virtual PCR in silico analysis of the local database 395 genome-nucleotide sequences of Vibrio cholerae in the presence of ICE element. The results showed widespread ICE member from toxigenic strains and nontoxigenic Vibrio cholerae O1 serotype. Thus all elements of ICE successfully typed three basic types – «Indian», «Mozambique», or «the SXT». In this case up to 40 % nontoxigenic strains O1 serovar and nonO1/nonO139 carried ICE element. When analyzed by PCR in vitro collection of 222 strains of Vibrio cholerae O1 serotype shows the presence of ICE element and determine its type in toxigenic strains isolated in recent years in the Russian Federation. All nontoxigenic O1, O139 and nonO1/nonO139 strains isolated in Russia, deprived of ICE element that differs from strains circulating in endemic cholera areas. This observation allows us to consider the presence of ICE element as a new epidemic marker «of invasive strains of» nontoxigenic Vibrio cholerae.

Identification of burden hotspots and risk factors for cholera in India: An observational study.

BackgroundEven though cholera has existed for centuries and many parts of the country have sporadic, endemic and epidemic cholera, it is still an under-recognized health problem in India. A Cholera Expert Group in the country was established to gather evidence and to prepare a road map for control of cholera in India. This paper identifies cholera burden hotspots and factors associated with an increased risk of the disease.Methodology/Principle findingsWe acquired district level data on cholera case reports of 2010–2015 from the Integrated Disease Surveillance Program. Socioeconomic characteristics and coverage of water and sanitation was obtained from the 2011 census. Spatial analysis was performed to identify cholera hotspots, and a zero-inflated Poisson regression was employed to identify the factors associated with cholera and predicted case count in the district. 27,615 cholera cases were reported during the 6-year period. Twenty-four of 36 states of India reported cholera during these years, and 13 states were classified as endemic. Of 641 districts, 78 districts in 15 states were identified as “hotspots” based on the reported cases. On the other hand, 111 districts in nine states were identified as “hotspots” from model-based predicted number of cases. The risk for cholera in a district was negatively associated with the coverage of literate persons, households using treated water source and owning mobile telephone, and positively associated with the coverage of poor sanitation and drainage conditions and urbanization level in the district.Conclusions/SignificanceThe study reaffirms that cholera continues to occur throughout a large part of India and identifies the burden hotspots and risk factors. Policymakers may use the findings of the article to develop a roadmap for prevention and control of cholera in India.

Epidemiology, determinants and dynamics of cholera in Pakistan: gaps and prospects for future research.

Cholera is one of the notifiable endemic diseases in Pakistan, but the reporting of cholera cases is still unsatisfactory. Most of the diagnosed cases are never reported to the relevant authorities. In the year 1993 - 2005, the country did not report any single case of cholera to the WHO. The objectives of this review were to understand the epidemiology and to identify the possible determinants of cholera infection in Pakistan. Medscape, Medline, PakMedinet and PubMed, was searched, using key words, epidemiology and determinants of cholera infection in Pakistan during 1995 - 2010. Morbidity and mortality due to cholera infection during 1995 - 2010, without any language restriction. Out of 27 articles published between 1995 - 2010, 17 articles were included in the review. Vibrio cholerae O139 identified as a major cause of infection in older age group, while O1 biotype of cholera as a predominant cause of cholera among young individuals. Mainly reported determinants of cholera in Pakistan include poor sanitation and hygiene practices, increased population density in urban areas, leading to rapid and unplanned urbanization of the major cities and climate change due to increased environmental pollution in Pakistan are plausible factors for endemicity of cholera in Pakistan. Cholera reporting as a notifiable disease to the relevant departments and timely action can prevent the risk of outbreaks. There is a need to identify specific behavioral and environmental determinants responsible for outbreaks and epidemics of cholera in Pakistan which can help to design appropriate preventive and control interventions.

Climate-driven endemic cholera is modulated by human mobility in a megacity

Although a differential sensitivity of cholera dynamics to climate variability has been reported in the spatially heterogeneous megacity of Dhaka, Bangladesh, the specific patterns of spread of the resulting risk within the city remain unclear. We build on an established probabilistic spatial model to investigate the importance and role of human mobility in modulating spatial cholera transmission. Mobility fluxes were inferred using a straightforward and generalizable methodology that relies on mapping population density based on a high resolution urban footprint product, and a parameter-free human mobility model. In accordance with previous findings, we highlight the higher sensitivity to the El Niño Southern Oscillation (ENSO) in the highly populated urban center than in the more rural periphery. More significantly, our results show that cholera risk is largely transmitted from the climate-sensitive core to the periphery of the city, with implications for the planning of control efforts. In addition, including human mobility improves the outbreak prediction performance of the model with an 11 month lead. The interplay between climatic and human mobility factors in cholera transmission is discussed from the perspective of the rapid growth of megacities across the developing world.

Retrospective Analysis of Serotype Switching of Vibrio cholerae O1 in a Cholera Endemic Region Shows It Is a Non-random Process.

Genomic data generated from clinical Vibrio cholerae O1 isolates collected over a five year period in an area of Kolkata, India with seasonal cholera outbreaks allowed a detailed genetic analysis of serotype switching that occurred from Ogawa to Inaba and back to Ogawa. The change from Ogawa to Inaba resulted from mutational disruption of the methyltransferase encoded by the wbeT gene. Re-emergence of the Ogawa serotype was found to result either from expansion of an already existing Ogawa clade or reversion of the mutation in an Inaba clade. Our data suggests that such transitions are not random events but rather driven by as yet unidentified selection mechanisms based on differences in the structure of the O1 antigen or in the serotype-determining wbeT gene.

Efficacy of a Single-Dose, Inactivated Oral Cholera Vaccine in Bangladesh

BackgroundA single-dose regimen of the current killed oral cholera vaccines that have been prequalified by the World Health Organization would make them more attractive for use against endemic and epidemic cholera. We conducted an efficacy trial of a single dose of the killed oral cholera vaccine Shanchol, which is currently given in a two-dose schedule, in an urban area in which cholera is highly endemic.MethodsNonpregnant residents of Dhaka, Bangladesh, who were 1 year of age or older were randomly assigned to receive a single dose of oral cholera vaccine or oral placebo. The primary outcome was vaccine protective efficacy against culture-confirmed cholera occurring 7 to 180 days after dosing. Prespecified secondary outcomes included protective efficacy against severely dehydrating culture-confirmed cholera during the same interval, against cholera and severe cholera occurring 7 to 90 versus 91 to 180 days after dosing, and against cholera and severe cholera according to age at baseline.ResultsA total of 101 episodes of cholera, 37 associated with severe dehydration, were detected among the 204,700 persons who received one dose of vaccine or placebo. The vaccine protective efficacy was 40% (95% confidence interval [CI], 11 to 60%; 0.37 cases per 1000 vaccine recipients vs. 0.62 cases per 1000 placebo recipients) against all cholera episodes, 63% (95% CI, 24 to 82%; 0.10 vs. 0.26 cases per 1000 recipients) against severely dehydrating cholera episodes, and 63% (95% CI, −39 to 90%), 56% (95% CI, 16 to 77%), and 16% (95% CI, −49% to 53%) against all cholera episodes among persons vaccinated at the age of 5 to 14 years, 15 or more years, and 1 to 4 years, respectively, although the differences according to age were not significant (P=0.25). Adverse events occurred at similar frequencies in the two groups.ConclusionsA single dose of the oral cholera vaccine was efficacious in older children (≥5 years of age) and in adults in a setting with a high level of cholera endemicity. (Funded by the Bill and Melinda Gates Foundation and others; ClinicalTrials.gov number, NCT02027207.)

Phylogenetic Diversity of Vibrio cholerae Associated with Endemic Cholera in Mexico from 1991 to 2008.

ABSTRACTAn outbreak of cholera occurred in 1991 in Mexico, where it had not been reported for more than a century and is now endemic. Vibrio cholerae O1 prototype El Tor and classical strains coexist with altered El Tor strains (1991 to 1997). Nontoxigenic (CTX−) V. cholerae El Tor dominated toxigenic (CTX+) strains (2001 to 2003), but V. cholerae CTX+ variant El Tor was isolated during 2004 to 2008, outcompeting CTX− V. cholerae. Genomes of six Mexican V. cholerae O1 strains isolated during 1991 to 2008 were sequenced and compared with both contemporary and archived strains of V. cholerae. Three were CTX+ El Tor, two were CTX− El Tor, and the remaining strain was a CTX+ classical isolate. Whole-genome sequence analysis showed the six isolates belonged to five distinct phylogenetic clades. One CTX− isolate is ancestral to the 6th and 7th pandemic CTX+ V. cholerae isolates. The other CTX− isolate joined with CTX− non-O1/O139 isolates from Haiti and seroconverted O1 isolates from Brazil and Amazonia. One CTX+ isolate was phylogenetically placed with the sixth pandemic classical clade and the V. cholerae O395 classical reference strain. Two CTX+ El Tor isolates possessing intact Vibrio seventh pandemic island II (VSP-II) are related to hybrid El Tor isolates from Mozambique and Bangladesh. The third CTX+ El Tor isolate contained West African-South American (WASA) recombination in VSP-II and showed relatedness to isolates from Peru and Brazil. Except for one isolate, all Mexican isolates lack SXT/R391 integrative conjugative elements (ICEs) and sensitivity to selected antibiotics, with one isolate resistant to streptomycin. No isolates were related to contemporary isolates from Asia, Africa, or Haiti, indicating phylogenetic diversity.

Predictive Time Series Analysis Linking Bengal Cholera with Terrestrial Water Storage Measured from Gravity Recovery and Climate Experiment Sensors.

Outbreaks of diarrheal diseases, including cholera, are related to floods and droughts in regions where water and sanitation infrastructure are inadequate or insufficient. However, availability of data on water scarcity and abundance in transnational basins, are a prerequisite for developing cholera forecasting systems. With more than a decade of terrestrial water storage (TWS) data from the Gravity Recovery and Climate Experiment, conditions favorable for predicting cholera occurrence may now be determined. We explored lead-lag relationships between TWS in the Ganges-Brahmaputra-Meghna basin and endemic cholera in Bangladesh. Since bimodal seasonal peaks in cholera in Bangladesh occur during spring and autumn seasons, two separate logistical models between TWS and disease time series (2002-2010) were developed. TWS representing water availability showed an asymmetrical, strong association with cholera prevalence in the spring (τ = -0.53; P < 0.001) and autumn (τ = 0.45; P < 0.001) up to 6 months in advance. One unit (centimeter of water) decrease in water availability in the basin increased odds of above normal cholera by 24% (confidence interval [CI] = 20-31%; P < 0.05) in the spring, while an increase in regional water by 1 unit, through floods, increased odds of above average cholera in the autumn by 29% (CI = 22-33%; P < 0.05).

Peru-15 (Choleragarde®), a live attenuated oral cholera vaccine, is safe and immunogenic in human immunodeficiency virus (HIV)-seropositive adults in Thailand

BackgroundMany areas with endemic and epidemic cholera report significant levels of HIV transmission. According to the World Health Organization (WHO), over 95% of reported cholera cases occur in Africa, which also accounts for nearly 70% of people living with HIV/AIDS globally. Peru-15, a promising single dose live attenuated oral cholera vaccine (LA-OCV), was previously found to be safe and immunogenic in cholera endemic areas. However, no data on the vaccine's safety among HIV-seropositive adults had been collected. MethodsThis study was a double-blinded, individually randomized, placebo-controlled trial enrolling HIV-seropositive adults, 18–45 years of age, conducted in Bangkok, Thailand, to assess the safety of Peru-15 in a HIV-seropositive cohort. Results32 HIV infected subjects were randomized to receive either a single oral dose of the Peru-15 vaccine with a buffer or a placebo (buffer only). No serious adverse events were reported during the follow-up period in either group. The geometric mean fold (GMF) rise in V. cholerae O1 El Tor specific antibody titers between baseline and 7 days after dosing was 32.0 (p<0.001) in the vaccine group compared to 1.6 (p<0.14) in the placebo group. Among the 16 vaccinees,14 vaccinees (87.5%) had seroconversion compared to 1 of 16 placebo recipients (6.3%). V. cholerae was isolated from the stool of one vaccinee, and found to be genetically identical to the Peru-15 vaccine strain. There were no significant changes in HIV viral load or CD4 T-cell counts between vaccine and placebo groups. ConclusionPeru-15 was shown to be safe and immunogenic in HIV-seropositive Thai adults.

Trends in the genomic epidemiology of Vibrio cholerae O1 isolated worldwide since 1961

Here we describe the international scenario of Vibrio cholerae with a comparative analysis of different aspects of typing. Representative V. cholerae strains (n=108) associated with endemic cholera regions from 29 states of India and worldwide were subjected to microbiological, molecular and phylogenetic study. All of the strains were V. cholerae serogroup O1 biotype El Tor and were typed according to both the new phage (NP) type and Basu & Mukherjee (BM) typing schemes. The predominant phage type was T-27 (NP)/T-4 (BM) (65.7%; n=71), followed by phage type T-27 (NP)/T-2 (BM) (14.8%; n=16), T-26 (NP)/T4 (BM) (12.0%; n=13), T-13 (NP)/T-4 (BM) (2.8%; n=3), T-20 (NP)/T-4 (BM) (1.9%; n=2), T-3 (NP)/T-4 (BM) (0.9%; n=1), T-23 (NP)/T-4 (BM) (0.9%; n=1) and T-24 (NP)/T-2 (BM) (0.9%; n=1). Mismatch amplification mutation assay PCR (MAMA-PCR) findings showed the dominance of ctxB El Tor genotype (77.1%; 54/70) from 1961–1991, whilst the next two epochs showed the supremacy of ctxB classical genotype. Multidrug-resistant strains showed resistance to erythromycin, streptomycin, trimethoprim/sulfamethoxazole, norfloxacin and ampicillin. The regional resistance of epidemic clones in India draws a layout of the rapid dissemination of resistance in the past 30 years and the necessity of proper treatment to protect populations at risk.

Role of phytoplankton in maintaining endemicity and seasonality of cholera in Bangladesh.

In Bangladesh, cholera is endemic and maintains a regular seasonal pattern. The role of phytoplankton in maintaining endemicity and seasonality of cholera was monitored in Matlab, Bangladesh. Phytoplankton and water samples were collected from two ponds bi-weekly for 1 year. The association of Vibrio cholerae O1 with phytoplankton was studied by culture and direct fluorescent antibody techniques. The bio-physicochemical parameters of water were measured and data for cases of cholera were collected from the records of Matlab hospital. The correlation of cholera cases with levels of phytoplankton, V. cholerae and bio-physicochemical parameters of water was carried out using Pearson's correlation coefficients. V. cholerae O1 survived for 48 days in association with Anabaena variabilis in a culturable state, but survived for a year in a viable but non-culturable (VBNC) state. V. cholerae survived for 12 and 32 days in a culturable state in control water (without algae) and water with algae, respectively. There was a significant correlation between changing levels of cholera cases in the community and the blue green algae and total phytoplankton in the aquatic environment. A significant correlation was also found between the cholera cases and chlorophyll-a and VBNC V. cholerae O1 in the aquatic environment. This study demonstrated the role of phytoplankton in maintaining endemicity and seasonality of cholera in Bangladesh.

Feasibility and effectiveness of oral cholera vaccine in an urban endemic setting in Bangladesh: a cluster randomised open-label trial

Cholera is endemic in Bangladesh with epidemics occurring each year. The decision to use a cheap oral killed whole-cell cholera vaccine to control the disease depends on the feasibility and effectiveness of vaccination when delivered in a public health setting. We therefore assessed the feasibility and protective effect of delivering such a vaccine through routine government services in urban Bangladesh and evaluated the benefit of adding behavioural interventions to encourage safe drinking water and hand washing to vaccination in this setting. We did this cluster-randomised open-label trial in Dhaka, Bangladesh. We randomly assigned 90 clusters (1:1:1) to vaccination only, vaccination and behavioural change, or no intervention. The primary outcome was overall protective effectiveness, assessed as the risk of severely dehydrating cholera during 2 years after vaccination for all individuals present at time of the second dose. This study is registered with ClinicalTrials.gov, number NCT01339845. Of 268,896 people present at baseline, we analysed 267,270: 94,675 assigned to vaccination only, 92,539 assigned to vaccination and behavioural change, and 80,056 assigned to non-intervention. Vaccine coverage was 65% in the vaccination only group and 66% in the vaccination and behavioural change group. Overall protective effectiveness was 37% (95% CI lower bound 18%; p=0·002) in the vaccination group and 45% (95% CI lower bound 24%; p=0·001) in the vaccination and behavioural change group. We recorded no vaccine-related serious adverse events. Our findings provide the first indication of the effect of delivering an oral killed whole-cell cholera vaccine to poor urban populations with endemic cholera using routine government services and will help policy makers to formulate vaccination strategies to reduce the burden of severely dehydrating cholera in such populations. Bill & Melinda Gates Foundation.

Microcystin-producing and non-producing cyanobacterial blooms collected from the Central India harbor potentially pathogenic Vibrio cholerae

On the basis of relative abundance, frequency and biovolume, the important value index ranks were assigned to individual cyanobacteria in phytoplankton samples collected from fourteen water resources of Central India. The mcyABDE genes were detected in all the blooms with Microcystis (-aeruginosa, –viridis, -panniformis, –botrys) as being the major constituent morphospecies. On the other hand, blooms composed of primarily Oscillatoria (-limosa,-agardhii, -laetevirens) along with Anabaena, Nostoc, Phormidium and Spirulina as sub-dominant forms exhibited quite a patchy distribution of one or the other mcy genes. Fifty percent of Microcystis- but none of the Oscillatoria dominant blooms produced microcystins–RR and desmethyl–RR at 0.03–0.41mgg−1 bloom dry mass. Traces of dissolved microcystin was detected in lake water, which is well below the WHO guideline. Irrespective of cyanobacterial composition and microcystin production ability, during the study period 43–64% of the cyanobacterial bloom samples exhibited association of viable but nonculturable forms of Vibrio cholerae O1 and O139, as evident from amplification of the antigen genes. We believe that spread of endemic cholera is the major threat associated with harmful algal blooms.

Detection of Vibrio cholerae O1 and O139 in environmental waters of rural Bangladesh: a flow-cytometry-based field trial.

Presence of Vibrio cholerae serogroups O1 and O139 in the waters of the rural area of Matlab, Bangladesh, was investigated with quantitative measurements performed with a portable flow cytometer. The relevance of this work relates to the testing of a field-adapted measurement protocol that might prove useful for cholera epidemic surveillance and for validation of mathematical models. Water samples were collected from different water bodies that constitute the hydrological system of the region, a well-known endemic area for cholera. Water was retrieved from ponds, river waters, and irrigation canals during an inter-epidemic time period. Each sample was filtered and analysed with a flow cytometer for a fast determination of V. cholerae cells contained in those environments. More specifically, samples were treated with O1- and O139-specific antibodies, which allowed precise flow-cytometry-based concentration measurements. Both serogroups were present in the environmental waters with a consistent dominance of V. cholerae O1. These results extend earlier studies where V. cholerae O1 and O139 were mostly detected during times of cholera epidemics using standard culturing techniques. Furthermore, our results confirm that an important fraction of the ponds' host populations of V. cholerae are able to self-sustain even when cholera cases are scarce. Those contaminated ponds may constitute a natural reservoir for cholera endemicity in the Matlab region. Correlations of V. cholerae concentrations with environmental factors and the spatial distribution of V. cholerae populations are also discussed.

Comparative effectiveness of different strategies of oral cholera vaccination in bangladesh: a modeling study.

BackgroundKilled, oral cholera vaccines have proven safe and effective, and several large-scale mass cholera vaccination efforts have demonstrated the feasibility of widespread deployment. This study uses a mathematical model of cholera transmission in Bangladesh to examine the effectiveness of potential vaccination strategies.Methods & FindingsWe developed an age-structured mathematical model of cholera transmission and calibrated it to reproduce the dynamics of cholera in Matlab, Bangladesh. We used the model to predict the effectiveness of different cholera vaccination strategies over a period of 20 years. We explored vaccination programs that targeted one of three increasingly focused age groups (the entire vaccine-eligible population of age one year and older, children of ages 1 to 14 years, or preschoolers of ages 1 to 4 years) and that could occur either as campaigns recurring every five years or as continuous ongoing vaccination efforts. Our modeling results suggest that vaccinating 70% of the population would avert 90% of cholera cases in the first year but that campaign and continuous vaccination strategies differ in effectiveness over 20 years. Maintaining 70% coverage of the population would be sufficient to prevent sustained transmission of endemic cholera in Matlab, while vaccinating periodically every five years is less effective. Selectively vaccinating children 1–14 years old would prevent the most cholera cases per vaccine administered in both campaign and continuous strategies.ConclusionsWe conclude that continuous mass vaccination would be more effective against endemic cholera than periodic campaigns. Vaccinating children averts more cases per dose than vaccinating all age groups, although vaccinating only children is unlikely to control endemic cholera in Bangladesh. Careful consideration must be made before generalizing these results to other regions.

Household Transmission of Vibrio cholerae in Bangladesh.

Background Vibrio cholerae infections cluster in households. This study's objective was to quantify the relative contribution of direct, within-household exposure (for example, via contamination of household food, water, or surfaces) to endemic cholera transmission. Quantifying the relative contribution of direct exposure is important for planning effective prevention and control measures.Methodology/Principal FindingsSymptom histories and multiple blood and fecal specimens were prospectively collected from household members of hospital-ascertained cholera cases in Bangladesh from 2001–2006. We estimated the probabilities of cholera transmission through 1) direct exposure within the household and 2) contact with community-based sources of infection. The natural history of cholera infection and covariate effects on transmission were considered. Significant direct transmission (p-value<0.0001) occurred among 1414 members of 364 households. Fecal shedding of O1 El Tor Ogawa was associated with a 4.9% (95% confidence interval: 0.9%–22.8%) risk of infection among household contacts through direct exposure during an 11-day infectious period (mean length). The estimated 11-day risk of O1 El Tor Ogawa infection through exposure to community-based sources was 2.5% (0.8%–8.0%). The corresponding estimated risks for O1 El Tor Inaba and O139 infection were 3.7% (0.7%–16.6%) and 8.2% (2.1%–27.1%) through direct exposure, and 3.4% (1.7%–6.7%) and 2.0% (0.5%–7.3%) through community-based exposure. Children under 5 years-old were at elevated risk of infection. Limitations of the study may have led to an underestimation of the true risk of cholera infection. For instance, available covariate data may have incompletely characterized levels of pre-existing immunity to cholera infection. Transmission via direct exposure occurring outside of the household was not considered.ConclusionsDirect exposure contributes substantially to endemic transmission of symptomatic cholera in an urban setting. We provide the first estimate of the transmissibility of endemic cholera within prospectively-followed members of households. The role of direct transmission must be considered when planning cholera control activities.

Descriptive characterization of the 2010 cholera outbreak in Nigeria.

BackgroundIn 2010, 18 States of Nigeria reported cholera outbreaks with a total of 41,787 cases including 1,716 deaths (case-fatality rate [CFR]: 4.1%). This exceeded the mean overall CFR of 2.4% reported in Africa from 2000–2005 and the WHO acceptable rate of 1%. We conducted a descriptive analysis of the 2010 cholera outbreak to determine its epidemiological and spatio-temporal characteristics.MethodsWe conducted retrospective analysis of line lists obtained from 10 of the 18 states that submitted line lists to the Federal Ministry of Health (FMOH). We described the outbreak by time, place and person and calculated the attack rates by state as well as the age- and sex-specific CFR from cholera cases for whom information on age, sex, place of residence, onset of symptoms and outcome were available.ResultsA total of 21,111 cases were reported with an overall attack rate and CFR of 47.8 cases /100,000 population and 5.1%, respectively. The CFR ranged in the states between 3.8% and 8.9%. The age-specific CFR was highest among individuals 65 years and above (14.6%). The epidemiological curve showed three peaks with increasing number of weekly reported cases. A geographical clustering of LGAs reporting cholera cases could be seen in all ten states. During the third peak which coincided with flooding in five states the majority of newly affected LGAs were situated next to LGAs with previously reported cholera cases, only few isolated outbreaks were seen.ConclusionOur study showed a cholera outbreak that grew in magnitude and spread to involve the whole northern part of the country. It also highlights challenges of suboptimal surveillance and response in developing countries as well as potential endemicity of cholera in the northern part of Nigeria. There is the need for a harmonized, coordinated approach to cholera outbreaks through effective surveillance and response with emphasis on training and motivating front line health workers towards timely detection, reporting and response. Findings from the report should be interpreted with caution due to the high number of cases with incomplete information, and lack of data from eight states.

High-frequency rugose exopolysaccharide production by Vibrio cholerae strains isolated in Haiti.

In October, 2010, epidemic cholera was reported for the first time in Haiti in over 100 years. Establishment of cholera endemicity in Haiti will be dependent in large part on the continued presence of toxigenic V. cholerae O1 in aquatic reservoirs. The rugose phenotype of V. cholerae, characterized by exopolysaccharide production that confers resistance to environmental stress, is a potential contributor to environmental persistence. Using a microbiologic medium promoting high-frequency conversion of smooth to rugose (S–R) phenotype, 80 (46.5%) of 172 V. cholerae strains isolated from clinical and environmental sources in Haiti were able to convert to a rugose phenotype. Toxigenic V. cholerae O1 strains isolated at the beginning of the epidemic (2010) were significantly less likely to shift to a rugose phenotype than clinical strains isolated in 2012/2013, or environmental strains. Frequency of rugose conversion was influenced by incubation temperature and time. Appearance of the biofilm produced by a Haitian clinical rugose strain (altered biotype El Tor HC16R) differed from that of a typical El Tor rugose strain (N16961R) by confocal microscopy. On whole-genome SNP analysis, there was no phylogenetic clustering of strains showing an ability to shift to a rugose phenotype. Our data confirm the ability of Haitian clinical (and environmental) strains to shift to a protective rugose phenotype, and suggest that factors such as temperature influence the frequency of transition to this phenotype.

Cholera at the crossroads: the association between endemic cholera and national access to improved water sources and sanitation.

We evaluated World Health Organization (WHO) national water and sanitation coverage levels and the infant mortality rate as predictors of endemic cholera in the 5-year period following water and sanitation coverage estimates using logistic regression, receiver operator characteristic curves, and different definitions of endemicity. Each was a significant predictors of endemic cholera at P < 0.001. Using a value of 250 for annual cases reported in 3 of 5 years, a national water access level of 71% has 65% sensitivity and 65% specificity in predicting endemic cholera, a sanitation access level of 39% has 63% sensitivity and 62% specificity, and an infant mortality rate of 65/1,000 has 67% sensitivity and 69% specificity. Our findings reveal the tradeoff between sensitivity and specificity for these predictors of endemic cholera and highlight the substantial uncertainty in the data. More accurate global surveillance data will enable more precise characterization of the benefits of improved water and sanitation.