The burden of cholera in the slums of Kolkata, India: data from a prospective, community based study

National Hospital-Based Sentinel Surveillance for Cholera in Bangladesh: Epidemiological Results from 2014 to 2021

Despite focusing on cholera burden, epidemiologic studies in Bangladesh tend to be limited in geographic scope. National-level cholera surveillance data can help inform cholera control strategies and assess the effectiveness of preventive measures. Hospital-based sentinel surveillance among patients with suspected diarrhea in different sites across Bangladesh has been conducted since 2014. We selected an age-stratified sample of 20 suspected cholera cases each week from each sentinel site, tested stool for the presence of Vibrio cholerae O1/O139 by culture, and characterized antibiotic susceptibility in a subset of culture-positive isolates. We estimated the odds of being culture positive among suspected cholera cases according to different potential risk factors. From May 4, 2014 through November 30, 2021, we enrolled 51,414 suspected cases from our sentinel surveillance sites. We confirmed V. cholerae O1 in 5.2% of suspected cases through microbiological culture. The highest proportion of confirmed cholera cases was from Chittagong (9.7%) and the lowest was from Rangpur Division (0.9%). Age, number of purges, duration of diarrhea, occupation, and season were the most relevant factors in distinguishing cholera-positive suspected cases from cholera-negative suspected cases. Nationwide surveillance data show that cholera is circulating in Bangladesh and the southern region is more affected than the northern region. Antimicrobial resistance patterns indicate that multidrug resistance (resistance to three or more classes of antibiotics) of V. cholerae O1 could be a major threat in the future. Alignment of these results with Bangladesh's cholera-control program will be the foundation for future research into the efficacy of cholera-control initiatives.

Seasonality of cholera in Kolkata and the influence of climate

BACKGROUND

Cholera in Kolkata remains endemic and the Indian city is burdened with a high number of annual cases. Climate change is widely considered to exacerbate cholera, however the precise relationship between climate and cholera is highly heterogeneous in space and considerable variation can be observed even within the Indian subcontinent. To date, relatively few studies have been conducted regarding the influence of climate on cholera in Kolkata.

METHODS

We considered 21 years of confirmed cholera cases from the Infectious Disease Hospital in Kolkata during the period of 1999-2019. We used Generalised Additive Modelling (GAM) to extract the non-linear relationship between cholera and different climatic factors; temperature, rainfall and sea surface temperature (SST). Peak associated lag times were identified using cross-correlation lag analysis.

RESULTS

Our findings revealed a bi-annual pattern of cholera cases with two peaks coinciding with the increase in temperature in summer and the onset of monsoon rains. Variables selected as explanatory variables in the GAM model were temperature and rainfall. Temperature was the only significant factor associated with summer cholera (mean temperature of 30.3 °C associated with RR of 3.8) while rainfall was found to be the main driver of monsoon cholera (550 mm total monthly rainfall associated with RR of 3.38). Lag time analysis revealed that the association between temperature and cholera cases in the summer had a longer peak lag time compared to that between rainfall and cholera during the monsoon. We propose several mechanisms by which these relationships are mediated.

CONCLUSIONS

Kolkata exhibits a dual-peak phenomenon with independent mediating factors. We suggest that the summer peak is due to increased bacterial concentration in urban water bodies, while the monsoon peak is driven by contaminated flood waters. Our results underscore the potential utility of preventative strategies tailored to these seasonal and climatic patterns, including efforts to reduce direct contact with urban water bodies in summer and to protect residents from flood waters during monsoon.

Estimating the proportion of clinically suspected cholera cases that are true Vibrio cholerae infections: A systematic review and meta-analysis

BACKGROUND

Cholera surveillance relies on clinical diagnosis of acute watery diarrhea. Suspected cholera case definitions have high sensitivity but low specificity, challenging our ability to characterize cholera burden and epidemiology. Our objective was to estimate the proportion of clinically suspected cholera that are true Vibrio cholerae infections and identify factors that explain variation in positivity.

METHODS AND FINDINGS

We conducted a systematic review of studies that tested ≥10 suspected cholera cases for V. cholerae O1/O139 using culture, PCR, and/or a rapid diagnostic test. We searched PubMed, Embase, Scopus, and Google Scholar for studies that sampled at least one suspected case between January 1, 2000 and April 19, 2023, to reflect contemporary patterns in V. cholerae positivity. We estimated diagnostic test sensitivity and specificity using a latent class meta-analysis. We estimated V. cholerae positivity using a random-effects meta-analysis, adjusting for test performance. We included 119 studies from 30 countries. V. cholerae positivity was lower in studies with representative sampling and in studies that set minimum ages in suspected case definitions. After adjusting for test performance, on average, 52% (95% credible interval (CrI): 24%, 80%) of suspected cases represented true V. cholerae infections. After adjusting for test performance and study methodology, the odds of a suspected case having a true infection were 5.71 (odds ratio 95% CrI: 1.53, 15.43) times higher when surveillance was initiated in response to an outbreak than in non-outbreak settings. Variation across studies was high, and a limitation of our approach was that we were unable to explain all the heterogeneity with study-level attributes, including diagnostic test used, setting, and case definitions.

CONCLUSIONS

In this study, we found that burden estimates based on suspected cases alone may overestimate the incidence of medically attended cholera by 2-fold. However, accounting for cases missed by traditional clinical surveillance is key to unbiased cholera burden estimates. Given the substantial variability in positivity between settings, extrapolations from suspected to confirmed cases, which is necessary to estimate cholera incidence rates without exhaustive testing, should be based on local data.

Mucosal and systemic immune responses to Vibrio cholerae infection and oral cholera vaccines (OCVs) in humans: a systematic review

INTRODUCTION

Cholera is an enteric disease caused by Vibrio cholerae, a water-borne pathogen, and characterized by severe diarrhea. Vaccines have been recommended for use by the WHO in resource-limited settings. Efficacies of the currently licensed cholera vaccines are not optimal in endemic settings and low in children below the age of five, a section of the population most susceptible to the disease. Development of next generation of cholera vaccines would require a detailed understanding of the required protective immune responses.

AREA COVERED

In this review, we revisit clinical trials which are focused on the early transcriptional mucosal responses elicited during Vibrio cholerae infection and upon vaccination along with summarizing various components of the effector immune response against Vibrio cholerae.

EXPERT OPINION

The inability of currently licensed killed/inactivated vaccines to elicit key inflammatory pathways locally may explain their restricted efficacy in endemic settings. More studies are required to understand the immunogenicity of the live attenuated cholera vaccine in these regions. Various extrinsic and intrinsic factors influence anti-cholera immunity and need to be considered to develop region-specific next generation vaccines.

Cholera Outbreaks in India, 2011–2020: A Systematic Review

Fecal contamination of water sources and open defecation have been linked to cholera outbreaks in India. However, a systematic review on the drivers responsible for these outbreaks has yet to be published. Here, we systematically review the published literature on cholera outbreaks in India between 2011 and 2020. We searched studies in English in three databases (MEDLINE, EMBASE, and Web of Science) and the Integrated Disease Surveillance Program that tracks cholera outbreaks throughout India. Two authors independently extracted data and assessed the quality of the included studies. Quantitative data on the modes of transmission reviewed in this study were assessed for any change over time between 2011–2015 and 2016–2020. Our search retrieved 10823 records initially, out of which 81 full-text studies were assessed for eligibility. Among these 81 studies, 20 were eligible for inclusion in this review. There were 565 reported outbreaks between 2011 and 2020 that led to 45,759 cases and 263 deaths. Outbreaks occurred throughout the year; however, they exploded with monsoons (June through September). In Tamil Nadu, a typical peak of cholera outbreaks was observed from December to January. Seventy-two percent (33,089/45,759) of outbreak-related cases were reported in five states, namely Maharashtra, West Bengal, Punjab, Karnataka, and Madhya Pradesh. Analysis of these outbreaks highlighted the main drivers of cholera including contaminated drinking water and food, inadequate sanitation and hygiene (including open defecation), and direct contact between households. The comparison between 2011–2015 and 2016–2020 showed a decreasing trend in the outbreaks that arose due to damaged water pipelines. Many Indians still struggle with open defecation, sanitation, and clean water access. These issues should be addressed critically. In addition, it is essential to interrupt cholera short-cycle transmission (mediated by households, stored drinking water and foodstuffs) during an outbreak. As cholera is associated with deprivation, socio-economic development is the only long-term solution.

Water, Sanitation, and Hygiene Practices in Urban Slums of Eastern India

Background

The Sustainable Development Goals identified universal access to water and sanitation facilities as key components for improving health. We assessed water, sanitation, and hygiene (WASH) practices and associated determinants among residents of urban slums in Kolkata, India.

Methods

Information on WASH practices was collected in 2 surveys (2018 and 2019) from participants of a prospective enteric fever surveillance conducted in 2 municipal wards of Kolkata. A composite WASH practice score was computed and a hierarchical stepwise multiple linear regression model constructed to identify key determinants of improved WASH score.

Results

Over 90% of households had access to piped water; 6% reported access to continuous supply. Adult women (61% in 2018; 45% in 2019) spent 20 minutes daily to fetch water. Access to improved latrines was almost universal, although 80% used shared facilities. Unhealthy disposal of children’s stools was reported in both rounds. Food hygiene practices were high, with most (>90%) washing uncooked items before eating; frequent consumption of street food items was reported.

Conclusions

The study area reported high WASH coverage. Unhygienic behavioral patterns predisposing to food- or water-borne diseases were also noted. Awareness building and sustainable community mobilization for food hygiene needs to be emphasized to ensure community well-being.

Cholera knowledge, socioeconomic and WaSH characteristics in Aden - Yemen, 2017: a community-based comparative survey

OBJECTIVES

To improve prevention and control response to the cholera outbreak, we sought to assess and compare the community's cholera awareness and needs in high and low epidemic areas in Aden.

METHODS

A community-based comparative survey was conducted in 2017. We used multi-stage cluster sampling. Eligible household heads in high and low epidemic areas were interviewed. The data collected from both areas using a pretested questionnaire.

RESULTS

Cholera cases and mortality were higher in high epidemic areas compared with low epidemic areas. Socioeconomic, water, sanitation, and hygienic conditions were poorer in high epidemic areas compared with low epidemic areas. Knowledge of cholera transmission and prevention was sub-optimal in both areas. We found a mismatch between the delivered education and distributed preventive materials.

CONCLUSIONS

Stakeholders should tailor the design, content, and implementation of future cholera prevention and control methods to meet the needs of the community. Future educational camping should focus on the transmission prevention, including vaccination. Education and sustainable interventions should be implemented to improve the water, sanitation, and hygiene.

Protracted cholera outbreak in the Central Region, Ghana, 2016

OBJECTIVE

On 24th October 2016, the Central Regional Health Directorate received report of a suspected cholera outbreak in the Cape Coast Metropolis (CCM). We investigated to confirm the diagnosis, identify risk factors and implement control measures.

DESIGN

We used a descriptive study followed by 1:2 unmatched case-control study.

DATA SOURCE

We reviewed medical records, conducted active case search and contact tracing, interviewed case-patients and their contacts and conducted environmental assessment. Case-patients' stool samples were tested with point of care test kits (SD Bioline Cholera Ag 01/0139) and sent to the Cape Coast Teaching Hospital Laboratory for confirmation.

MAIN OUTCOMES

Cause of outbreak, risk factors associated with spread of outbreak.

RESULTS

Vibrio cholerae serotype Ogawa caused the outbreak. There was no mortality. Of 704 case-patients, 371(52.7%) were males and 55(7.8%) were aged under-five years. The median age was 23 years (interquartile range: 16-32 years). About a third 248(35.2%) of the case patients were aged 15-24 years. The University of Cape Coast subdistrict was the epicenter with 341(48.44%) cases. Compared to controls, cholera case-patients were more likely to have visited Cholera Treatment Centers (CTC) (aOR=12.1, 95%CI: 1.5-101.3), drank pipe-borne water (aOR=11.7, 95%CI: 3.3-41.8), or drank street-vended sachet water (aOR=11.0, 95%CI: 3.7-32.9). Open defecation and broken sewage pipes were observed in the epicenter.

CONCLUSION

Vibrio cholerae serotype Ogawa caused the CCM cholera outbreak mostly affecting the youth. Visiting CTC was a major risk factor. Prompt case-management, contact tracing, health education, restricting access to CTC and implementing water sanitation and hygiene activities helped in the control.

FUNDING

This work was supported by Ghana Field Epidemiology and Laboratory Training Program (GFELTP), University of Ghana.

The history of OCV in India and barriers remaining to programmatic introduction

Cholera-endemic Eastern India has played an important role in the development of oral cholera vaccines (OCV) through conduct of pivotal trials in Kolkata which led to the registration of the first low-cost bivalent killed whole cell OCV in India in 2009, and subsequent prequalification by the World Health Organization prequalification in 2011. Odisha hosted an influential early demonstration project for use of the vaccine in a high-risk population and provided data and lessons that were crucial input in the Vaccine Investment Strategy developed by Gavi, the Vaccine Alliance in 2013. With Gavi's decision to finance an OCV stockpile, the demand for OCV surged and vaccine has been deployed with great success worldwide in areas of need in response to outbreaks and disasters, most notably in Africa. However, although India is considered one of the highest burden countries, no further use of OCV has occurred since the demonstration project in Odisha in 2011. In this paper we will summarize the important contributions of India to the development and use of OCV and discuss the possible barriers to OCV introduction as a public health tool to control cholera.

Mapping cholera outbreaks and antibiotic resistant Vibrio cholerae in India: An assessment of existing data and a scoping review of the literature

Although fluid and electrolyte replenishment remains the mainstay of clinical management of cholera, antibiotics are an important component of the strategy for clinical management of moderate to severe cases of cholera. The emergence of antibiotic resistance (ABR) in Vibrio cholerae has led to difficulties in case management. The past decade has also seen the development of cheap and effective oral cholera vaccines (OCVs). In addition to the two-dose strategy for widespread immunization, OCVs have also been shown to be effective in containing outbreaks using a single-dose schedule. In this scoping review we map the states and union territories (SUTs) of India which are prone to cholera outbreaks followed by a scoping review of peer-reviewed publications about ABR outbreaks of cholera employing the Arksey and O'Malley framework. Using the data reported by the Integrated Disease Surveillance Program (IDSP), we identified 559 outbreaks of cholera between 2009 and 2017, affecting 27 SUTs. We defined SUTs which had reported outbreaks in at least three out of the last five years (2012-2016) or had experienced two or more outbreaks in the same year in at least two of the last five years to be outbreak-prone. The scoping review identified 62 ABR outbreaks, with four SUTs accounting for two-thirds of them: West Bengal (14), Maharashtra (10), Odisha (10) and Delhi (7). Overall, this scoping review suggests that there is an increasing trend of ABR in Vibrio cholerae isolated from outbreaks in India. This opens up avenues for exploring the role of antibiotic stewardship in the clinical management of diarrhea, the institution of vaccination as an infection prevention intervention to reduce selection pressure, and the deployment of high quality surveillance systems which report accurate, real-time data allowing appropriate and timely public health responses. It is crucial to counter the issue of ABR in cholera before it assumes a menacing magnitude.

Economic burden of cholera in Asia

BACKGROUND

The economic burden data can provide a basis to inform investments in cholera control and prevention activities. However, treatment costs and productivity loss due to cholera are not well studied.

METHODS

We included Asian countries that either reported cholera cases to the World Health Organization (WHO) in 2015 or were considered cholera endemic in 2015 global burden of disease study. Public health service delivery costs for hospitalization and outpatient costs, out-of-pocket costs to patients and households, and lost productivity were extracted from literature. A probabilistic multivariate sensitivity analysis was conducted for key outputs using Monte Carlo simulation. Scenario analyses were conducted using data from the WHO cholera reports and conservative and liberal disease burden estimates.

RESULTS

Our analysis included 14 Asian countries that were estimated to have a total of 850,000 cholera cases and 25,500 deaths in 2015 While, the WHO cholera report documented around 60,000 cholera cases and 28 deaths. We estimated around $20.2 million (I$74.4 million) in out-of-pocket expenditures, $8.5 million (I$30.1 million) in public sector costs, and $12.1 million (I$43.7 million) in lost productivity in 2015. Lost productivity due to premature deaths was estimated to be $985.7 million (I$3,638.6 million). Our scenario analyses excluding mortality costs showed that the economic burden ranged from 20.3% ($8.3 million) to 139.3% ($57.1 million) in high and low scenarios when compared to the base case scenario ($41 million) and was least at 10.1% ($4.1 million) when estimated based on cholera cases reported to WHO.

CONCLUSION

The economic burden of cholera in Asia provides a better understanding of financial offsets that can be achieved, and the value of investments on cholera control measures. With a clear understanding of the limitations of the underlying assumptions, the information may be used in economic evaluations and policy decisions.

Mr.Vc: a database of microarray and RNA-seq of Vibrio cholerae

Gram-negative bacterium Vibrio cholerae is the causative agent of cholera, a life-threatening diarrheal disease. During its infectious cycle, V. cholerae routinely switches niches between aquatic environment and host gastrointestinal tract, in which V. cholerae modulates its transcriptome pattern accordingly for better survival and proliferation. A comprehensive resource for V. cholerae transcriptome will be helpful for cholera research, including prevention, diagnosis and intervention strategies. In this study, we constructed a microarray and RNA-seq database of V. cholerae (Mr.Vc), containing gene transcriptional expression data of 145 experimental conditions of V. cholerae from various sources, covering 25 937 entries of differentially expressed genes. In addition, we collected relevant information including gene annotation, operons they may belong to and possible interaction partners of their protein products. With Mr.Vc, users can easily find transcriptome data they are interested in, such as the experimental conditions in which a gene of interest was differentially expressed in, or all genes that were differentially expressed in an experimental condition. We believe that Mr.Vc database is a comprehensive data repository dedicated to V. cholerae and could be a useful resource for all researchers in related fields. Mr.Vc is available for free at http://bioinfo.life.hust.edu.cn/mrvc.

Individual and Household Risk Factors for Symptomatic Cholera Infection: A Systematic Review and Meta-analysis

Background

Cholera has caused 7 global pandemics, including the current one which has been ongoing since 1961. A systematic review of risk factors for symptomatic cholera infection has not been previously published.

Methods

In accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we performed a systematic review and meta-analysis of individual and household risk factors for symptomatic cholera infection.

Results

We identified 110 studies eligible for inclusion in qualitative synthesis. Factors associated with symptomatic cholera that were eligible for meta-analysis included education less than secondary level (summary odds ratio [SOR], 2.64; 95% confidence interval [CI], 1.41-4.92; I2 = 8%), unimproved water source (SOR, 3.48; 95% CI, 2.18-5.54; I2 = 77%), open container water storage (SOR, 2.03; 95% CI, 1.09-3.76; I2 = 62%), consumption of food outside the home (SOR, 2.76; 95% CI, 1.62-4.69; I2 = 64%), household contact with cholera (SOR, 2.91; 95% CI, 1.62-5.25; I2 = 89%), water treatment (SOR, 0.37; 95% CI, .21-.63; I2 = 74%), and handwashing (SOR, 0.29; 95% CI, .20-.43; I2 = 37%). Other notable associations with symptomatic infection included income/wealth, blood group, gastric acidity, infant breastfeeding status, and human immunodeficiency virus infection.

Conclusions

We identified potential risk factors for symptomatic cholera infection including environmental characteristics, socioeconomic factors, and intrinsic patient factors. Ultimately, a combination of interventional approaches targeting various groups with risk-adapted intensities may prove to be the optimal strategy for cholera control.

Environmental Surveillance of Vibrio cholerae O1/O139 in the Five African Great Lakes and Other Major Surface Water Sources in Uganda

Cholera is a major public health problem in the African Great Lakes basin. Two hypotheses might explain this observation, namely the lakes are reservoirs of toxigenic Vibrio cholerae O1 and O139 bacteria, or cholera outbreaks are a result of repeated pathogen introduction from the neighboring communities/countries but the lakes facilitate the introductions. A prospective study was conducted in Uganda between February 2015 and January 2016 in which 28 selected surface water sources were tested for the presence of V. cholerae species using cholera rapid test and multiplex polymerase chain reaction. Of 322 water samples tested, 35 (10.8%) were positive for V. cholerae non O1/non O139 and two samples tested positive for non-toxigenic atypical V. cholerae O139. None of the samples tested had toxigenic V. cholerae O1 or O139 that are responsible for cholera epidemics. The Lake Albert region registered the highest number of positive tests for V. cholerae non O1/non O139 at 47% (9/19). The peak period for V. cholerae non O1/non O139 positive tests was in March–July 2015 which coincided with the first rainy season in Uganda. This study showed that the surface water sources, including the African Great Lakes in Uganda, are less likely to be reservoirs for the observed V. cholerae O1 or O139 epidemics, though they are natural habitats for V. cholerae non O1/non O139 and atypical non-toxigenic V. cholerae O139. Further studies by WGS tests of non-toxigenic atypical V. cholerae O139 and physicochemical tests of surface water sources that supports V. cholerae should be done to provide more information. Since V. cholerae non O1/non O139 may cause other human infections, their continued surveillance is needed to understand their potential pathogenicity.

Confirmation of cholera by rapid diagnostic test amongst patients admitted to the cholera treatment centre in Uvira, Democratic Republic of the Congo

INTRODUCTION

Cholera is endemic in the Eastern provinces of the Democratic Republic of the Congo since 1978, and Uvira in South-Kivu has been reporting suspected cholera cases nearly every week for over a decade. The clinical case definition for suspected cholera is relatively non-specific, and cases are rarely confirmed by laboratory methods, especially in endemic settings. This may lead to over-estimation of cholera cases and limit effective public health responses.

METHODS AND RESULTS

Between April 2016 and November 2017, 69% of the 2,059 patients admitted to the Uvira Cholera Treatment Centre (CTC) were tested for cholera with rapid diagnostic tests (RDTs). Of those admitted as suspected cholera cases, only 40% tested positive for cholera, equivalent to an estimated annual incidence of suspected/confirmed cholera in Uvira of 43.8 and 16.3 cases per 10,000 inhabitants respectively. A multivariable logistic regression indicates that boys aged 2 to 4 years, girls aged 5 to 15 years and adult men are respectively 1.9, 2.1 and 1.8 times more likely to test positive than adult women. On the contrary, boys under 2 are 10 times less likely to test positive. The odds of testing positive also increase as weekly admissions to the CTC rise, with up to a 5-fold increase observed during the weeks with the highest numbers of admissions compared to the lowest ones. Other predictors of cholera confirmation include duration of stay at the CTC, clinical outcome of admission, lower weekly rainfall and area of residence in Uvira, with the northern part of town having the highest confirmation rate.

CONCLUSION

Cholera is an on-going public health problem in Uvira but the majority of suspected cases admitted to the CTC were found to be negative for cholera after RDT testing. These findings may have important implications for cholera control strategies in favour of interventions that address cholera and other diarrhoeal diseases alike.

Identification of priority health conditions for field-based screening in urban slums in Bangalore, India

BACKGROUND

Urban slums are characterised by unique challenging living conditions, which increase their inhabitants' vulnerability to specific health conditions. The identification and prioritization of the key health issues occurring in these settings is essential for the development of programmes that aim to enhance the health of local slum communities effectively. As such, the present study sought to identify and prioritise the key health issues occurring in urban slums, with a focus on the perceptions of health professionals and community workers, in the rapidly growing city of Bangalore, India.

METHODS

The study followed a two-phased mixed methods design. During Phase I of the study, a total of 60 health conditions belonging to four major categories: - 1) non-communicable diseases; 2) infectious diseases; 3) maternal and women's reproductive health; and 4) child health - were identified through a systematic literature review and semi-structured interviews conducted with health professionals and other relevant stakeholders with experience working with urban slum communities in Bangalore. In Phase II, the health issues were prioritised based on four criteria through a consensus workshop conducted in Bangalore.

RESULTS

The top health issues prioritized during the workshop were: diabetes and hypertension (non-communicable diseases category), dengue fever (infectious diseases category), malnutrition and anaemia (child health, and maternal and women's reproductive health categories). Diarrhoea was also selected as a top priority in children. These health issues were in line with national and international reports that listed them as top causes of mortality and major contributors to the burden of diseases in India.

CONCLUSIONS

The results of this study will be used to inform the development of technologies and the design of interventions to improve the health outcomes of local communities. Identification of priority health issues in the slums of other regions of India, and in other low and lower middle-income countries, is recommended.

Gessner B, Munier A, A. Mengel M. Multi-site cholera surveillance within the African Cholera Surveillance Network shows endemicity in Mozambique, 2011-2015

Background

Mozambique suffers recurrent annual cholera outbreaks especially during the rainy season between October to March. The African Cholera Surveillance Network (Africhol) was implemented in Mozambique in 2011 to generate accurate detailed surveillance data to support appropriate interventions for cholera control and prevention in the country.

Methodology/Principal findings

Africhol was implemented in enhanced surveillance zones located in the provinces of Sofala (Beira), Zambézia (District Mocuba), and Cabo Delgado (Pemba City). Data were also analyzed from the three outbreak areas that experienced the greatest number of cases during the time period under observation (in the districts of Cuamba, Montepuez, and Nampula). Rectal swabs were collected from suspected cases for identification of Vibrio cholerae, as well as clinical, behavioral, and socio-demographic variables. We analyzed factors associated with confirmed, hospitalized, and fatal cholera using multivariate logistic regression models.

A total of 1,863 suspected cases and 23 deaths (case fatality ratio (CFR), 1.2%) were reported from October 2011 to December 2015. Among these suspected cases, 52.2% were tested of which 23.5% were positive for Vibrio cholerae O1 Ogawa. Risk factors independently associated with the occurrence of confirmed cholera were living in Nampula city district, the year 2014, human immunodeficiency virus infection, and the primary water source for drinking.

Conclusions/Significance

Cholera was endemic in Mozambique during the study period with a high CFR and identifiable risk factors. The study reinforces the importance of continued cholera surveillance, including a strong laboratory component. The results enhanced our understanding of the need to target priority areas and at-risk populations for interventions including oral cholera vaccine (OCV) use, and assess the impact of prevention and control strategies. Our data were instrumental in informing integrated prevention and control efforts during major cholera outbreaks in recent years.

Cholera is a major public health problem in many countries in sub-Saharan Africa. In Mozambique, annual outbreaks occur but the place and time may vary. Africhol was implemented in Mozambique in 2011 to generate more detailed information on disease burden and characteristics to support appropriate interventions for cholera control and prevention in the country. The study was conducted in six different zones, where patients with cholera symptoms seeking care at a health facility were asked questions on socio-demographic characteristics, their symptoms, and behaviors that may increase cholera risk. Stool samples were also taken to test for the presence of cholera infection (Vibrio cholerae). Among the 1,863 patients, more than half were tested for cholera, and among those tested, less than one in four was infected with the pathogen. About 1% of patients died from cholera. Our study helps to understand the burden of cholera in different areas of the country, and the characteristics of the people infected. It is important to continue the surveillance of this disease to choose the most appropriate control and preventive interventions, and to apply them in precisely the right place.

Prevalence of Vibrio cholerae O1 serogroup in Assam, India: A hospital-based study

BACKGROUND & OBJECTIVES

Although cholera remains to be an important public health problem, studies on reliable population-based estimates of laboratory confirmed cholera in endemic areas are limited worldwide. The aim of this hospital-based study was to evaluate the prevalence of Vibrio cholerae serogroup in Assam, India, during 2003-2013.

METHODS

Stool samples/rectal swabs were collected from acute watery diarrhoea (AWD) cases during 2003-2013 and processed by standard microbiological procedures. Antibiotic sensitivity test was done following the Clinical and Laboratory Standards Institute guidelines. Year-wise epidemiological trend of cholera was analyzed.

RESULTS

Cholera contributed to 3.93 per cent of AWD cases. In Assam, cholera was found to be more prevalent in the rural areas (6.7%) followed by the tea gardens (5.06%), urban slum (1.9%) and urban areas (1.4%). Highest proportion of cholera (13.7%) was observed in 0-10 yr age group. Of them, 11.5 per cent belonged to 0-5 yr age group. V. cholerae O1 El Tor serotype Ogawa was the predominant isolate. Multiple drug-resistant isolates of V. cholerae O1 Ogawa were reported in the study.

INTERPRETATION & CONCLUSIONS

Emergence of resistance amongst V. cholerae towards many antibiotics is a matter of concern. Hence, continuous surveillance for diarrhoeal disorders is necessary to control the future outbreaks of cholera in this region.

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

Background

Even 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 findings

We 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/Significance

The 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.

Effect of modelling slum populations on influenza spread in Delhi

OBJECTIVES

This research studies the impact of influenza epidemic in the slum and non-slum areas of Delhi, the National Capital Territory of India, by taking proper account of slum demographics and residents' activities, using a highly resolved social contact network of the 13.8 million residents of Delhi.

METHODS

An SEIR model is used to simulate the spread of influenza on two different synthetic social contact networks of Delhi, one where slums and non-slums are treated the same in terms of their demographics and daily sets of activities and the other, where slum and non-slum regions have different attributes.

RESULTS

Differences between the epidemic outcomes on the two networks are large. Time-to-peak infection is overestimated by several weeks, and the cumulative infection rate and peak infection rate are underestimated by 10-50%, when slum attributes are ignored.

CONCLUSIONS

Slum populations have a significant effect on influenza transmission in urban areas. Improper specification of slums in large urban regions results in underestimation of infections in the entire population and hence will lead to misguided interventions by policy planners.

Incidence of severe diarrhoea due to Vibrio cholerae in the catchment area of six surveillance hospitals in Bangladesh

Cholera is an important public health problem in Bangladesh. Interventions to prevent cholera depend on their cost-effectiveness which in turn depends on cholera incidence. Hospital-based diarrhoeal disease surveillance has been ongoing in six Bangladeshi hospitals where a systematic proportion of patients admitted with diarrhoea were enrolled and tested for Vibrio cholerae. However, incidence calculation using only hospital data underestimates the real disease burden because many ill persons seek treatment elsewhere. We conducted a healthcare utilization survey in the catchment areas of surveillance hospitals to estimate the proportion of severe diarrhoeal cases that were admitted to surveillance hospitals and estimated the population-based incidence of severe diarrhoea due to V. cholerae by combining both hospital surveillance and catchment area survey data. The estimated incidence of severe diarrhoea due to cholera ranged from 0.3 to 4.9/1000 population in the catchment area of surveillance hospitals. In children aged <5 years, incidence ranged from 1.0 to 11.0/1000 children. Diarrhoeal deaths were most common in the Chhatak Hospital's catchment area (18.5/100 000 population). This study provides a credible estimate of the incidence of severe diarrhoea due to cholera in Bangladesh, which can be used to assess the cost-effectiveness of cholera prevention activities.

Trials and tribulations of conducting interventional studies in urban slums of a developing country: Experiences from Kolkata, India

Experimental studies involving human subjects provide most internally valid evidences in epidemiological research due to their robust methodology. While conducting population-based interventional studies, to achieve external validity, inclusion of information from vulnerable groups like urban slum-dwellers of the developing world, in the epidemiological estimates is of paramount importance. The challenges faced while conducting 2 consecutive large-scale, community-based vaccine trials in urban slums of Kolkata, India are presented in this article. Interventions in these communities often get constrained by issues pertaining to human rights and benefits, socio-cultural factors, political environment, methodological shortcomings in addition to the challenges in ensuring community participation. While conducting these trials although we intermittently faced obstacles, by virtue of having a long term and robust surveillance system and developing a trusted relationship between the researchers, community leaders and residents we were able to come up with a commendable community participation which culminated into the success of the interventions. Bridging the gap between research and field operations by incorporating knowledge gathered from interventional studies and making strategies to improve health conditions of these informal settlers is a major unfulfilled agenda. We believe the lessons learnt during our research will help researchers while developing efficient interventions in similar setting.

Updated global burden of cholera in endemic countries

BACKGROUND

The global burden of cholera is largely unknown because the majority of cases are not reported. The low reporting can be attributed to limited capacity of epidemiological surveillance and laboratories, as well as social, political, and economic disincentives for reporting. We previously estimated 2.8 million cases and 91,000 deaths annually due to cholera in 51 endemic countries. A major limitation in our previous estimate was that the endemic and non-endemic countries were defined based on the countries' reported cholera cases. We overcame the limitation with the use of a spatial modelling technique in defining endemic countries, and accordingly updated the estimates of the global burden of cholera.

METHODS/PRINCIPAL FINDINGS

Countries were classified as cholera endemic, cholera non-endemic, or cholera-free based on whether a spatial regression model predicted an incidence rate over a certain threshold in at least three of five years (2008-2012). The at-risk populations were calculated for each country based on the percent of the country without sustainable access to improved sanitation facilities. Incidence rates from population-based published studies were used to calculate the estimated annual number of cases in endemic countries. The number of annual cholera deaths was calculated using inverse variance-weighted average case-fatality rate (CFRs) from literature-based CFR estimates. We found that approximately 1.3 billion people are at risk for cholera in endemic countries. An estimated 2.86 million cholera cases (uncertainty range: 1.3m-4.0m) occur annually in endemic countries. Among these cases, there are an estimated 95,000 deaths (uncertainty range: 21,000-143,000).

CONCLUSION/SIGNIFICANCE

The global burden of cholera remains high. Sub-Saharan Africa accounts for the majority of this burden. Our findings can inform programmatic decision-making for cholera control.

Identifying the most sensitive and specific sign and symptom combinations for cholera: results from an analysis of laboratory-based surveillance data from Haiti, 2012-2013

Since October 2010, over 700,000 cholera cases have been reported in Haiti. We used data from laboratory-based surveillance for diarrhea in Haiti to evaluate the sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) of the cholera case definitions recommended by the World Health Organization (WHO). From April 2012 to May 2013, we tested 1,878 samples from hospitalized patients with acute watery diarrhea; 1,178 (62.7%) yielded Vibrio cholerae O1. The sensitivity and specificity of the WHO case definition for cholera in an epidemic setting were 91.3% and 43.1%, respectively, and the PPV and NPV were 72.8% and 74.8%, respectively. The WHO case definition for cholera in an area where cholera is not known to be present had lower sensitivity (63.1%) and NPV (55.1%) but higher specificity (74.2%) and PPV (80.0%). When laboratory diagnostic testing is not immediately available, clinicians can evaluate signs and symptoms to more accurately identify cholera patients.

Flexibility of oral cholera vaccine dosing-a randomized controlled trial measuring immune responses following alternative vaccination schedules in a cholera hyper-endemic zone

BACKGROUND

A bivalent killed whole cell oral cholera vaccine has been found to be safe and efficacious for five years in the cholera endemic setting of Kolkata, India, when given in a two dose schedule, two weeks apart. A randomized controlled trial revealed that the immune response was not significantly increased following the second dose compared to that after the first dose. We aimed to evaluate the impact of an extended four week dosing schedule on vibriocidal response.

METHODOLOGY/PRINCIPAL FINDINGS

In this double blind randomized controlled non-inferiority trial, 356 Indian, non-pregnant residents aged 1 year or older were randomized to receive two doses of oral cholera vaccine at 14 and 28 day intervals. We compared vibriocidal immune responses between these schedules. Among adults, no significant differences were noted when comparing the rates of seroconversion for V. cholerae O1 Inaba following two dose regimens administered at a 14 day interval (55%) vs the 28 day interval (58%). Similarly, no differences in seroconversion were demonstrated in children comparing the 14 (80%) and 28 day intervals (77%). Following 14 and 28 day dosing intervals, vibriocidal response rates against V. cholerae O1 Ogawa were 45% and 49% in adults and 73% and 72% in children respectively. Responses were lower for V. cholerae O139, but similar between dosing schedules for adults (20%, 20%) and children (28%, 20%).

CONCLUSIONS/SIGNIFICANCE

Comparable immune responses and safety profiles between the two dosing schedules support the option for increased flexibility of current OCV dosing. Further operational research using a longer dosing regimen will provide answers to improve implementation and delivery of cholera vaccination in endemic and epidemic outbreak scenarios.

Vaccine development and deployment: opportunities and challenges in India

The Indian economy is among the fastest growing economies in the world. The country forayed into manufacturing vaccines starting with a few public-sector manufacturers in the late 1960s but has emerged as the major supplier of basic Expanded Programme on Immunization vaccines to the United Nations Children's Fund (UNICEF) because of substantial private-sector investment in the area. The Indian vaccine industry is now able to produce new and more complex vaccines such as the meningitis, Haemophilus influenzae type b, and pneumococcal conjugate vaccines, rotavirus vaccine and influenza A (H1N1) vaccines. This has been possible because of an attractive investment environment, effective and innovative governmental support, international partnerships and the growing in-country technical work force. A large number of vaccines, including those mentioned, is available and administered in the private sector within the country, but India has been slow in introducing new vaccines in its publically funded programs. Growth in the economy and technological accomplishments are not reflected in a reduction in health inequalities, and India continues to contribute significantly to global child mortality figures. This paper reviews the development of the Indian vaccine industry, policy support for it and its current status. It also highlights opportunities and challenges for the introduction of new and underutilized vaccines at home.

Infectious disease burden in Gujarat (2005-2011): comparison of selected infectious disease rates with India

Background

India is known to be endemic to numerous infectious diseases. The infectious disease profile of India is changing due to increased human environmental interactions, urbanisation and climate change. There are also predictions of explosive growth in infectious and zoonotic diseases. The Integrated Disease Surveillance Project (IDSP) was implemented in Gujarat in 2004.

Methods

We analysed IDSP data on seven laboratory confirmed infectious diseases from 2005–2011 on temporal and spatial trends and compared this to the National Health Profile (NHP) data for the same period and with other literature. We chose laboratory cases data for Enteric fever, Cholera, Hepatitis, Dengue, Chikungunya, Measles and Diphtheria in the state since well designed vertical programs do not exist for these diseases. Statistical and GIS analysis was done using appropriate software.

Results

Our analysis shows that the existing surveillance system in the state is predominantly reporting urban cases. There are wide variations among reported cases within the state with reports of Enteric fever and Measles being less than half of the national average, while Cholera, Viral Hepatitis and Dengue being nearly double.

Conclusions

We found some limitations in the IDSP system with regard to the number of reporting units and cases in the background of a mixed health system with multiplicity of treatment providers and payment mechanisms. Despite these limitations, IDSP can be strengthened into a comprehensive surveillance system capable of tackling the challenge of reversing the endemicity of these diseases and preventing the emergence of others.

Cholera outbreaks in India

Cholera is a global health problem as several thousands of cases and deaths occur each year. The unique epidemiologic attribute of the disease is its propensity to occur as outbreaks that may flare-up into epidemics, if not controlled. The causative bacterial pathogen Vibrio cholerae prevails in the environment and infects humans whenever there is a breakdown in the public health component. The Indian subcontinent is vulnerable to this disease due its vast coastlines with areas of poor sanitation, unsafe drinking water, and overcrowding. Recently, it was shown that climatic conditions also play a major role in the persistence and spread of cholera. Constant change in the biotypes and serotypes of V. cholerae are also important aspects that changes virulence and survival of the pathogen. Such continuous changes increase the infection ability of the pathogen affecting the susceptible population including the children. The short-term carrier status of V. cholerae has been studied well at community level and this facet significantly contributes to the recurrence of cholera. Several molecular tools recognized altering clonality of V. cholerae in relation with the advent of a serogroup or serotype. Rapid identification systems were formulated for the timely detection of the pathogen so as to identify and control the outbreak and institute proper treatment of the patients. The antimicrobials used in the past are no longer useful in the treatment of cholera as V. cholerae has acquired several mechanisms for multiple antimicrobial resistance. This upsurge in antimicrobial resistance directly influences the management of the disease. This chapter provides an overview of cholera prevalence in India, possible sources of infection, and molecular epidemiology along with antimicrobial resistance of V. cholerae.

Risk factors for cholera transmission in Haiti during inter-peak periods: insights to improve current control strategies from two case-control studies

Two community-based density case-control studies were performed to assess risk factors for cholera transmission during inter-peak periods of the ongoing epidemic in two Haitian urban settings, Gonaives and Carrefour. The strongest associations were: close contact with cholera patients (sharing latrines, visiting cholera patients, helping someone with diarrhoea), eating food from street vendors and washing dishes with untreated water. Protective factors were: drinking chlorinated water, receiving prevention messages via television, church or training sessions, and high household socioeconomic level. These findings suggest that, in addition to contaminated water, factors related to direct and indirect inter-human contact play an important role in cholera transmission during inter-peak periods. In order to reduce cholera transmission in Haiti intensive preventive measures such as hygiene promotion and awareness campaigns should be implemented during inter-peak lulls, when prevention activities are typically scaled back.

Children's health in slum settings

Rapid urbanisation in the 20th century has been accompanied by the development of slums. Nearly one-third of the world's population and more than 60% of urban populations in the least developed countries live in slums, including hundreds of millions of children. Slums are areas of broad social and health disadvantage to children and their families due to extreme poverty, overcrowding, poor water and sanitation, substandard housing, limited access to basic health and education services, and other hardships (eg, high unemployment, violence). Despite the magnitude of this problem, very little is known about the potential impact of slum life on the health of children and adolescents. Statistics that show improved mortality and health outcomes in cities are based on aggregated data and may miss important intraurban disparities. Limited but consistent evidence suggests higher infant and under-five years mortality for children residing in slums compared with non-slum areas. Children suffer from higher rates of diarrhoeal and respiratory illness, malnutrition and have lower vaccination rates. Mothers residing in slums are more poorly educated and less likely to receive antenatal care and skilled birth assistance. Adolescents have earlier sexual debut and higher rates of HIV, and adopt risky behaviours influenced by their social environment. We also know little about the consequences of this form of early childhood on long-term health-related behaviour (eg, diet and exercise) and non-communicable disease outcomes, such as obesity, heart disease and mental illness. Further attention to understanding and addressing child health in slum settings is an important priority for paediatricians and those committed to child health worldwide.

Laboratory-confirmed cholera and rotavirus among patients with acute diarrhea in four hospitals in Haiti, 2012-2013

An outbreak of cholera began in Haiti in October of 2010. To understand the progression of epidemic cholera in Haiti, in April of 2012, we initiated laboratory-enhanced surveillance for diarrheal disease in four Haitian hospitals in three departments. At each site, we sampled up to 10 hospitalized patients each week with acute watery diarrhea. We tested 1,616 specimens collected from April 2, 2012 to March 28, 2013; 1,030 (63.7%) specimens yielded Vibrio cholerae, 13 (0.8%) specimens yielded Shigella, 6 (0.4%) specimens yielded Salmonella, and 63 (3.9%) specimens tested positive for rotavirus. Additionally, 13.5% of children < 5 years old tested positive for rotavirus. Of 1,030 V. cholerae isolates, 1,020 (99.0%) isolates were serotype Ogawa, 9 (0.9%) isolates were serotype Inaba, and 1 isolate was non-toxigenic V. cholerae O139. During 1 year of surveillance, toxigenic cholera continued to be the main cause of acute diarrhea in hospitalized patients, and rotavirus was an important cause of diarrhea-related hospitalizations in children.

Risk map of cholera infection for vaccine deployment: the eastern Kolkata case

BACKGROUND

Despite advancement of our knowledge, cholera remains a public health concern. During March-April 2010, a large cholera outbreak afflicted the eastern part of Kolkata, India. The quantification of importance of socio-environmental factors in the risk of cholera, and the calculation of the risk is fundamental for deploying vaccination strategies. Here we investigate socio-environmental characteristics between high and low risk areas as well as the potential impact of vaccination on the spatial occurrence of the disease.

METHODS AND FINDINGS

The study area comprised three wards of Kolkata Municipal Corporation. A mass cholera vaccination campaign was conducted in mid-2006 as the part of a clinical trial. Cholera cases and data of the trial to identify high risk areas for cholera were analyzed. We used a generalized additive model (GAM) to detect risk areas, and to evaluate the importance of socio-environmental characteristics between high and low risk areas. During the one-year pre-vaccination and two-year post-vaccination periods, 95 and 183 cholera cases were detected in 111,882 and 121,827 study participants, respectively. The GAM model predicts that high risk areas in the west part of the study area where the outbreak largely occurred. High risk areas in both periods were characterized by poor people, use of unsafe water, and proximity to canals used as the main drainage for rain and waste water. Cholera vaccine uptake was significantly lower in the high risk areas compared to low risk areas.

CONCLUSION

The study shows that even a parsimonious model like GAM predicts high risk areas where cholera outbreaks largely occurred. This is useful for indicating where interventions would be effective in controlling the disease risk. Data showed that vaccination decreased the risk of infection. Overall, the GAM-based risk map is useful for policymakers, especially those from countries where cholera remains to be endemic with periodic outbreaks.

Determinants of health care seeking for diarrheal illness in young children in urban slums of Kolkata, India

Maternal practices regarding children's health care have been recognized as an important factor associated with mortality rates among children < 5 years of age. We focused on health care-seeking practices of primary caretakers of children < 5 years of age with diarrheal disease in Kolkata. We interviewed caretakers of 1,058 children in a baseline survey and 6,077 children on six subsequent surveys. The prevalence of diarrhea during the preceding 2 weeks was 7.9% in the baseline survey and 5.7% (lowest 3.5% to highest 7.8%) in subsequent surveys. Multivariate logistic regression showed that formal education of primary caretakers was associated with seeking care outside the home (odds ratio [OR] = 15.5; 95% confidence interval [CI] [2.5-85.7]; P = 0.002). Multinomial logistic regression showed that formal education of the primary caretaker (OR = 21.4; 95% CI [3.2-139.0]; P = 0.002) and presence of dry mouth during diarrhea (OR = 17.3; 95% CI [2.7-110.9]; P = 0.003) were associated with seeking care from licensed providers compared with the children for whom care was not sought outside of the home. This health care utilization and attitudes survey (HUAS) can serve as a tool to identify the factors that influence a better health care-seeking pattern in urban slums of Kolkata.

A ubiquitous method for street scale spatial data collection and analysis in challenging urban environments: mapping health risks using spatial video in Haiti

BACKGROUND

Fine-scale and longitudinal geospatial analysis of health risks in challenging urban areas is often limited by the lack of other spatial layers even if case data are available. Underlying population counts, residential context, and associated causative factors such as standing water or trash locations are often missing unless collected through logistically difficult, and often expensive, surveys. The lack of spatial context also hinders the interpretation of results and designing intervention strategies structured around analytical insights. This paper offers a ubiquitous spatial data collection approach using a spatial video that can be used to improve analysis and involve participatory collaborations. A case study will be used to illustrate this approach with three health risks mapped at the street scale for a coastal community in Haiti.

METHODS

Spatial video was used to collect street and building scale information, including standing water, trash accumulation, presence of dogs, cohort specific population characteristics, and other cultural phenomena. These data were digitized into Google Earth and then coded and analyzed in a GIS using kernel density and spatial filtering approaches. The concentrations of these risks around area schools which are sometimes sources of diarrheal disease infection because of the high concentration of children and variable sanitary practices will show the utility of the method. In addition schools offer potential locations for cholera education interventions.

RESULTS

Previously unavailable fine scale health risk data vary in concentration across the town, with some schools being proximate to greater concentrations of the mapped risks. The spatial video is also used to validate coded data and location specific risks within these "hotspots".

CONCLUSIONS

Spatial video is a tool that can be used in any environment to improve local area health analysis and intervention. The process is rapid and can be repeated in study sites through time to track spatio-temporal dynamics of the communities. Its simplicity should also be used to encourage local participatory collaborations.

Vibrio cholerae/mimicus in fecal microbiota of healthy children in a cholera endemic urban slum setting in Kolkata, India

During a double-blind, randomized, placebo-controlled probiotic trial among 3758 children residing in an urban slum in Kolkata, India, Vibrio cholerae/mimicus was detected in fecal microbiota of healthy children. The importance of this finding in the local, regional and global transmission of cholera is discussed.

Cholera risk factors, Papua New Guinea, 2010

BACKGROUND

Cholera is newly emergent in Papua New Guinea but may soon become endemic. Identifying the risk factors for cholera provides evidence for targeted prevention and control measures.

METHODS

We conducted a hospital-based case-control study to identify cholera risk factors. Using stool culture as the standard, we evaluated a cholera point of care test in the field.

RESULTS

176 participants were recruited: 54 cases and 122 controls. Independent risk factors for cholera were: being over 20 years of age (aOR 2.5; 95%CI 1.1, 5.4), defecating in the open air (or river) (aOR 4.5; 95% CI 1.4, 14.4) and knowing someone who travelled to a cholera affected area (aOR 4.1; 95%CI 1.6, 10.7); while the availability of soap for handwashing at home was protective (aOR 0.41; 95%CI 0.19, 0.87). Those reporting access to a piped water distribution system in the home were twice as likely to report the availability of soap for handwashing. The sensitivity and specificity of the rapid test were 72% (95% CI 47-90) and 71% (95%CI 44-90%).

CONCLUSIONS

Improving population access to the piped water distribution system and sanitation will likely reduce transmission by enabling enhanced hygiene and limiting the contamination of water sources. The One step V. cholerae O1/O139 Antigen Test is of limited utility for clinical decision making in a hospital setting with access to traditional laboratory methods. Settlement dwellers and mobile populations of all age groups should be targeted for interventions in Papua New Guinea.

Clinical, epidemiological, and spatial characteristics of Vibrio parahaemolyticus diarrhea and cholera in the urban slums of Kolkata, India

Background

There is not much information on the differences in clinical, epidemiological and spatial characteristics of diarrhea due to V. cholerae and V. parahaemolyticus from non-coastal areas. We investigated the differences in clinical, epidemiological and spatial characteristics of the two Vibrio species in the urban slums of Kolkata, India.

Methods

The data of a cluster randomized cholera vaccine trial were used. We restricted the analysis to clusters assigned to placebo. Survival analysis of the time to the first episode was used to analyze risk factors for V. parahaemolyticus diarrhea or cholera. A spatial scan test was used to identify high risk areas for cholera and for V. parahaemolyticus diarrhea.

Results

In total, 54,519 people from the placebo clusters were assembled. The incidence of cholera (1.30/1000/year) was significantly higher than that of V. parahaemolyticus diarrhea (0.63/1000/year). Cholera incidence was inversely related to age, whereas the risk of V. parahaemolyticus diarrhea was age-independent. The seasonality of diarrhea due to the two Vibrio species was similar. Cholera was distinguished by a higher frequency of severe dehydration, and V. parahaemolyticus diarrhea was by abdominal pain. Hindus and those who live in household not using boiled or treated water were more likely to have V. parahaemolyticus diarrhea. Young age, low socioeconomic status, and living closer to a project healthcare facility were associated with an increased risk for cholera. The high risk area for cholera differed from the high risk area for V. parahaemolyticus diarrhea.

Conclusion

We report coexistence of the two vibrios in the slums of Kolkata. The two etiologies of diarrhea had a similar seasonality but had distinguishing clinical features. The risk factors and the high risk areas for the two diseases differ from one another suggesting different modes of transmission of these two pathogens.

Outbreak of cholera in the East Akim Municipality of Ghana following unhygienic practices by small-scale gold miners, November 2010

BACKGROUND

In October 2010 an outbreak of cholera began among a group of small-scale gold miners in the East-Akim Municipality (EAM), Eastern Region. We investigated to verify the diagnosis, identify risk factors and recommend control measures.

METHODS

We conducted a descriptive investigation, active case-search and an unmatched case-control study. A cholera case-patient was a person with acute watery diarrhoea, with or without vomiting in EAM from 1st October to 20(th) November, 2010. Stool from case-patients and water samples were taken for laboratory diagnosis. We performed univariate and bivariate analysis using epi-info version 3.3.

RESULTS

Of 136 case-patients, 77 (56.6%) were males, of which 40% were miners or from miners households. Index case, a 20 yr-old male miner from Apapam village reported on October 13(th), and case-patients peaked (18.4%) 20 days later. Attack rate was 2/1000 population with no fatality. Ages ranged from 1-84 years; mean of 34±18 yrs. Age-group 20-29 yrs was mostly affected (30.1%) with Apapam village having most case-patients (19.9%). Vibrio cholera serotype ogawa was isolated from stool samples. The main water source, Birim river was polluted by small-scale miners through defecation, post-defecation baths and sand-washings. Compared to controls, case-patients were more likely to have drunk from Birim-River [OR= 6.99, 95% CI: 2.75-18].

CONCLUSION

Vibrio cholera serotype ogawa caused the EAM cholera-outbreak affecting many young adult-males. Drinking water from contaminated community-wide -River was the major risk factors. Boiling or chlorination of water was initiated based on our recommendations and this controlled the outbreak.

Bayesian structured additive regression modeling of epidemic data: application to cholera

Background

A significant interest in spatial epidemiology lies in identifying associated risk factors which enhances the risk of infection. Most studies, however, make no, or limited use of the spatial structure of the data, as well as possible nonlinear effects of the risk factors.

Methods

We develop a Bayesian Structured Additive Regression model for cholera epidemic data. Model estimation and inference is based on fully Bayesian approach via Markov Chain Monte Carlo (MCMC) simulations. The model is applied to cholera epidemic data in the Kumasi Metropolis, Ghana. Proximity to refuse dumps, density of refuse dumps, and proximity to potential cholera reservoirs were modeled as continuous functions; presence of slum settlers and population density were modeled as fixed effects, whereas spatial references to the communities were modeled as structured and unstructured spatial effects.

Results

We observe that the risk of cholera is associated with slum settlements and high population density. The risk of cholera is equal and lower for communities with fewer refuse dumps, but variable and higher for communities with more refuse dumps. The risk is also lower for communities distant from refuse dumps and potential cholera reservoirs. The results also indicate distinct spatial variation in the risk of cholera infection.

Conclusion

The study highlights the usefulness of Bayesian semi-parametric regression model analyzing public health data. These findings could serve as novel information to help health planners and policy makers in making effective decisions to control or prevent cholera epidemics.

The global burden of cholera

OBJECTIVE

To estimate the global burden of cholera using population-based incidence data and reports.

METHODS

Countries with a recent history of cholera were classified as endemic or non-endemic, depending on whether they had reported cholera cases in at least three of the five most recent years. The percentages of the population in each country that lacked access to improved sanitation were used to compute the populations at risk for cholera, and incidence rates from published studies were applied to groups of countries to estimate the annual number of cholera cases in endemic countries. The estimates of cholera cases in non-endemic countries were based on the average numbers of cases reported from 2000 to 2008. Literature-based estimates of cholera case-fatality rates (CFRs) were used to compute the variance-weighted average cholera CFRs for estimating the number of cholera deaths.

FINDINGS

About 1.4 billion people are at risk for cholera in endemic countries. An estimated 2.8 million cholera cases occur annually in such countries (uncertainty range: 1.4-4.3) and an estimated 87,000 cholera cases occur in non-endemic countries. The incidence is estimated to be greatest in children less than 5 years of age. Every year about 91,000 people (uncertainty range: 28,000 to 142,000) die of cholera in endemic countries and 2500 people die of the disease in non-endemic countries.

CONCLUSION

The global burden of cholera, as determined through a systematic review with clearly stated assumptions, is high. The findings of this study provide a contemporary basis for planning public health interventions to control cholera.

Costs of illness due to endemic cholera

Economic analyses of cholera immunization programmes require estimates of the costs of cholera. The Diseases of the Most Impoverished programme measured the public, provider, and patient costs of culture-confirmed cholera in four study sites with endemic cholera using a combination of hospital- and community-based studies. Families with culture-proven cases were surveyed at home 7 and 14 days after confirmation of illness. Public costs were measured at local health facilities using a micro-costing methodology. Hospital-based studies found that the costs of severe cholera were US$32 and US$47 in Matlab and Beira. Community-based studies in North Jakarta and Kolkata found that cholera cases cost between US$28 and US$206, depending on hospitalization. Patients' cost of illness as a percentage of average monthly income were 21% and 65% for hospitalized cases in Kolkata and North Jakarta, respectively. This burden on families is not captured by studies that adopt a provider perspective.

Cholera: a great global concern

Cholera, caused by the infection of toxigenic Vibrio cholerae (V. cholerae) to humans, is a life threatening diarrheal disease with epidemic and pandemic potential. The V. cholerae, both O1 and O139 serogroups, produce a potent enterotoxin (cholera toxin) responsible for the lethal symptoms of the disease. The O1 serogroup has two biotypes (phenotypes), classical and El Tor; each of which has two major serotypes (based on antigenic responses), Ogawa and Inaba and the extremely rare Hikojima. V. cholerae O1 strains interconvert and switch between the Ogawa and Inaba serotypes. Fluid and electrolyte replacement is the mainstay of treatment of cholera patients; the severe cases require antibiotic treatment to reduce the duration of illness and replacement of fluid intake. The antibiotic therapy currently has faced difficulties due to the rapid emergence and spread of multidrug resistant V. cholerae causing several outbreaks in the globe. Currently, cholera has been becoming endemic in an increasing number of geographical areas, reflecting a failure in implementation of control measures. However, the current safe oral vaccines lower the number of resistant infections and could thus represent an effective intervention measure to control antibiotic resistance in cholera. Overall, the priorities for cholera control remain public health interventions through improved drinking water, sanitation, surveillance and access to health care facilities, and further development of safe, effective and appropriate vaccines. Thus, this review describes the facts and phenomena related to the disease cholera, which is still a great threat mainly to the developing countries, and hence a grave global concern too.

A cholera outbreak among semi-nomadic pastoralists in northeastern Uganda: epidemiology and interventions

In sub-Saharan Africa, many nomadic pastoralists have begun to settle in permanent communities as a result of long-term water, food, and civil insecurity. Little is known about the epidemiology of cholera in these emerging semi-nomadic populations. We report the results of a case-control study conducted during a cholera outbreak among semi-nomadic pastoralists in the Karamoja sub-region of northeastern Uganda in 2010. Data from 99 cases and 99 controls were analysed. In multivariate analyses, risk factors identified were: residing in the same household as another cholera case [adjusted odds ratio (aOR) 6·67, 95% confidence interval (CI) 2·83-15·70], eating roadside food (aOR 2·91, 95% CI 1·24-6·81), not disposing of children's faeces in a latrine (aOR 15·76, 95% CI 1·54-161·25), not treating drinking water with chlorine (aOR 3·86, 95% CI 1·63-9·14), female gender (aOR 2·43, 95% CI 1·09-5·43), and childhood age (10-17 years) (aOR 7·14, 95% CI 1·97-25·83). This is the first epidemiological study of cholera reported from a setting of semi-nomadic pastoralism in sub-Saharan Africa. Public health interventions among semi-nomadic pastoralists should include a two-faceted approach to cholera prevention: intensive health education programmes to address behaviours inherited from insecure nomadic lifestyles, as well as improvements in water and sanitation infrastructure. The utilization of community-based village health teams provides an important method of implementing such activities.

Product Development Partnerships: Case studies of a new mechanism for health technology innovation

There is a continuing need for new health technologies to address the disease burdens of developing countries. In the last decade Product Development Partnerships (PDP) have emerged that are making important contributions to the development of these technologies. PDPs are a form of public private partnerships that focus on health technology development. PDPs reflect the current phase in the history of health technology development: the Era of Partnerships, in which the public and private sectors have found productive ways to collaborate. Successful innovation depends on addressing six determinants of innovation. We examine four case studies of PDPs and show how they have addressed the six determinants to achieve success.