Understanding the cholera epidemic, Haiti

Mitigating Cholera in the Aftermath of Cyclone Idai

Catastrophic damage and floods followed the deadliest cyclone on record for the Southern Hemisphere. In the aftermath of Cyclone Idai, a cholera outbreak was detected. The global stockpile of oral cholera vaccine was rapidly deployed to counter this fast-growing epidemic. We urge the international community to continue to highlight the importance of water, sanitation, and hygiene as the long-term goal for controlling cholera and meeting the 2030 Sustainable Development Goals.

Environmental health in Australia: overlooked and underrated

Improvements in environmental health have had the most significant impact on health status. In Australia, life expectancy has significantly increased through provision of vaccination, safe food and drinking water, appropriate sewage disposal and other environmental health measures. Yet the profession that is instrumental in delivering environmental health services at the local community level is overlooked. Rarely featuring in mainstream media, the successes of Environmental Health Officers (EHOs) are invisible to the general public. As a consequence, students entering university are unaware of the profession and its significant role in society. This has resulted in there being too few EHOs to meet the current regulatory requirements, much less deal with the emerging environmental health issues arising as a consequence of changing global conditions including climate change. To futureproof Australian society and public health this workforce issue, and the associated oversight of environmental health must be addressed now.

Low case fatality during 2017 cholera outbreak in Borno State, North Eastern Nigeria

Background:

Cholera is endemic in sub-Saharan Africa, especially in areas affected by natural disaster and human conflict. Northeastern Nigeria is experiencing a health crisis due to the destruction of essential amenities such as health infrastructure, sanitation facilities, water supplies, and human resources by Boko Haram insurgents. In 2017, a cholera outbreak occurred in five local government areas (LGAs) hosting internally displaced persons. The Nigeria Center for Disease Control, World Health Organization, Mĕdecins Sans Frontiĕres International, and several other organizations supported disease containment. An emergency operating center (EOC) established by the State Ministry of Health (SMoH) then coordinated the outbreak response.

Methods:

We conducted a retrospective analysis of data extracted from the line list utilized by the SMoH to investigate outbreaks. We evaluated the outbreak by time, place, and person. Attack rate by LGA and age-specific case fatality rate (CFR) was calculated based on cases with complete records for age, sex, place of residence, date of symptom onset, and disease outcome.

Results:

A total of 5889 cholera cases were reported from five LGAs with an overall attack rate of 395.3/100,000 population. Among 4956 cases with documented outcome, the overall CFR was 0.87%, with CFR ranging from 0% to 6.98% by LGA. The age-specific CFR was highest among those aged ≥60 years (1.92%) and least among those aged 20–29 years at 0.3%. The epidemiological curve revealed two peaks that coincided with periods of heavy rain and flooding.

Conclusion:

This study reports on the largest ever documented cholera outbreak in five LGAs in Borno State. The outbreak was focused in LGA hit hardest by the destructive activities of insurgents and then spread to neighboring LGAs. The low CFR recorded in this cholera outbreak was achieved through timely detection, reporting, and response by the coordinated efforts of the EOC established by the SMoH that harmonized the outbreak response.

The case-area targeted rapid response strategy to control cholera in Haiti: a four-year implementation study

BACKGROUND

In October 2010, Haiti was struck by a large-scale cholera epidemic. The Haitian government, UNICEF and other international partners launched an unprecedented nationwide alert-response strategy in July 2013. Coordinated NGOs recruited local rapid response mobile teams to conduct case-area targeted interventions (CATIs), including education sessions, household decontamination by chlorine spraying, and distribution of chlorine tablets. An innovative red-orange-green alert system was also established to monitor the epidemic at the communal scale on a weekly basis. Our study aimed to describe and evaluate the exhaustiveness, intensity and quality of the CATIs in response to cholera alerts in Haiti between July 2013 and June 2017.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed the response to 7,856 weekly cholera alerts using routine surveillance data and severity criteria, which was based on the details of 31,306 notified CATIs. The odds of CATI response during the same week (exhaustiveness) and the number of complete CATIs in responded alerts (intensity and quality) were estimated using multivariate generalized linear mixed models and several covariates. CATIs were carried out significantly more often in response to red alerts (adjusted odds ratio (aOR) [95%-confidence interval, 95%-CI], 2.52 [2.22-2.87]) compared with orange alerts. Significantly more complete CATIs were carried out in response to red alerts compared with orange alerts (adjusted incidence ratio (aIR), 1.85 [1.73-1.99]). Over the course of the eight-semester study, we observed a significant improvement in the exhaustiveness (aOR, 1.43 [1.38-1.48] per semester) as well as the intensity and quality (aIR, 1.23 [1.2-1.25] per semester) of CATI responses, independently of funds available for the strategy. The odds of launching a CATI response significantly decreased with increased rainfall (aOR, 0.99 [0.97-1] per each accumulated cm). Response interventions were significantly heterogeneous between NGOs, communes and departments.

CONCLUSIONS/SIGNIFICANCE

The implementation of a nationwide case-area targeted rapid response strategy to control cholera in Haiti was feasible albeit with certain obstacles. Such feedback from the field and ongoing impact studies will be very informative for actors and international donors involved in cholera control and elimination in Haiti and in other affected countries.

Wave 2 strains of atypical Vibrio cholerae El Tor caused the 2009-2011 cholera outbreak in Papua New Guinea

Vibrio cholerae is the causative agent of cholera, a globally important human disease for at least 200 years. In 2009–2011, the first recorded cholera outbreak in Papua New Guinea (PNG) occurred. We conducted genetic and phenotypic characterization of 21 isolates of V. cholerae, with whole-genome sequencing conducted on 2 representative isolates. The PNG outbreak was caused by an atypical El Tor strain harbouring a tandem repeat of the CTX prophage on chromosome II. Whole-genome sequence data, prophage structural analysis and the absence of the SXT integrative conjugative element was indicative that the PNG isolates were most closely related to strains previously isolated in South-East and East Asia with affiliations to global wave 2 strains. This finding suggests that the cholera outbreak in PNG was caused by an exotic (non-endemic) strain of V. cholerae that originated in South-East Asia.

Haitian Variant Vibrio cholerae O1 Strains Manifest Higher Virulence in Animal Models

Vibrio cholerae causes fatal diarrheal disease cholera in humans due to consumption of contaminated water and food. To instigate the disease, the bacterium must evade the host intestinal innate immune system; penetrate the mucus layer of the small intestine, adhere and multiply on the surface of microvilli and produce toxin(s) through the action of virulence associated genes. V. cholerae O1 that has caused a major cholera outbreak in Haiti contained several unique genetic signatures. These novel traits are used to differentiate them from the canonical El Tor strains. Several studies reported the spread of these Haitian variant strains in different parts of the world including Asia and Africa, but there is a paucity of information on the clinical consequence of these genetic changes. To understand the impact of these changes, we undertook a study involving mice and rabbit models to evaluate the pathogenesis. The colonization ability of Haitian variant strain in comparison to canonical El Tor strain was found to be significantly more in both suckling mice and rabbit model. Adult mice also displayed the same results. Besides that, infection patterns of Haitian variant strains showed a completely different picture. Increased mucosal damaging, colonization, and inflammatory changes were observed through hematoxylin-eosin staining and transmission electron microscopy. Fluid accumulation ability was also significantly higher in rabbit model. Our study indicated that these virulence features of the Haitian variant strain may have some association with the severe clinical outcome of the cholera patients in different parts of the world.

Epidemiological and molecular forensics of cholera recurrence in Haiti

Cholera has affected Haiti with damping waves of outbreaks since October 2010. However, mechanisms behind disease persistence during lull periods remain poorly understood. By mid 2014, cholera transmission seemed to only persist in the northern part of Haiti. Meanwhile, cholera appeared nearly extinct in the capital, Port-au-Prince, where it eventually exploded in September 2014. This study aimed to determine whether this outbreak was caused by local undetected cases or by re-importation of the disease from the north. Applying an integrated approach between November 2013 and November 2014, we assessed the temporal and spatial dynamics of cholera using routine surveillance data and performed population genetics analyses of 178 Vibrio cholerae O1 clinical isolates. The results suggest that the northern part of the country exhibited a persisting metapopulation pattern with roaming oligoclonal outbreaks that could not be effectively controlled. Conversely, undetected and unaddressed autochthonous low-grade transmission persisted in the Port-au-Prince area, which may have been the source of the acute outbreak in late-2014. Cholera genotyping is a simple but powerful tool to adapt control strategies based on epidemic specificities. In Haiti, these data have already yielded significant progress in cholera surveillance, which is a key component of the strategy to eventually eliminate cholera.

Rainfall as a driver of epidemic cholera: Comparative model assessments of the effect of intra-seasonal precipitation events

The correlation between cholera epidemics and climatic drivers, in particular seasonal tropical rainfall, has been studied in a variety of contexts owing to its documented relevance. Several mechanistic models of cholera transmission have included rainfall as a driver by focusing on two possible transmission pathways: either by increasing exposure to contaminated water (e.g. due to worsening sanitary conditions during water excess), or water contamination by freshly excreted bacteria (e.g. due to washout of open-air defecation sites or overflows). Our study assesses the explanatory power of these different modeling structures by formal model comparison using deterministic and stochastic models of the type susceptible-infected-recovered-bacteria (SIRB). The incorporation of rainfall effects is generalized using a nonlinear function that can increase or decrease the relative importance of the large precipitation events. Our modelling framework is tested against the daily epidemiological data collected during the 2015 cholera outbreak within the urban context of Juba, South Sudan. This epidemic is characterized by a particular intra-seasonal double peak on the incidence in apparent relation with particularly strong rainfall events. Our results show that rainfall-based models in both their deterministic and stochastic formulations outperform models that do not account for rainfall. In fact, classical SIRB models are not able to reproduce the second epidemiological peak, thus suggesting that it was rainfall-driven. Moreover we found stronger support across model types for rainfall acting on increased exposure rather than on exacerbated water contamination. Although these results are context-specific, they stress the importance of a systematic and comprehensive appraisal of transmission pathways and their environmental forcings when embarking in the modelling of epidemic cholera.

Locals get travellers' diarrhoea too: risk factors for diarrhoeal illness and pathogenic Escherichia coli infection across an urban-rural gradient in Ecuador

OBJECTIVES

Diarrhoea is a common and well-studied cause of illness afflicting international travellers. However, traveller's diarrhoea can also result from travel between high and low disease transmission regions within a country, which is the focus of this study.

METHODS

We recruited participants for a case-control study of diarrhoea at four sites along an urban-rural gradient in Northern Ecuador: Quito, Esmeraldas, Borbón and rural communities outside of Borbón. At each of these sites, approximately 100 subjects with diarrhoea (cases) were recruited from Ministry of Health clinics and were age-matched with subjects visiting the same clinics for other complaints (controls).

RESULTS

Travellers to urban destinations had higher risk of diarrhoea and diarrhoeagenic Escherichia coli (DEC) infections. Travel to Quito was associated with diarrhoea (aOR = 2.01, 95% CI = 1.10-3.68) and travel to Guayaquil (another urban centre in Ecuador) was associated with Diffuse Adherent E. coli infection (OR = 2.09, 95% CI = 1.01-4.33). Compared to those not travelling, urban origins were also associated with greater risk of diarrhoea in Esmeraldas (aOR = 2.28, 95% CI = 1.20-4.41), and with higher risk of diarrhoeagenic E. coli infections in Quito (aOR = 2.61, 95% CI = 1.16-5.86), with >50% of travel from Quito and Esmeraldas specified to another urban destination.

CONCLUSIONS

This study suggests that individuals travelling from lower-transmission regions (rural areas) to higher transmission regions (urban centres) within a single country are at a greater risk of acquiring a diarrhoea-related illness. Investments to improve water, sanitation and hygiene conditions in urban areas could have impacts on outlying rural areas within a given country.

A Metagenomic Approach to Evaluating Surface Water Quality in Haiti

The cholera epidemic that occurred in Haiti post-earthquake in 2010 has resulted in over 9000 deaths during the past eight years. Currently, morbidity and mortality rates for cholera have declined, but cholera cases still occur on a daily basis. One continuing issue is an inability to accurately predict and identify when cholera outbreaks might occur. To explore this surveillance gap, a metagenomic approach employing environmental samples was taken. In this study, surface water samples were collected at two time points from several sites near the original epicenter of the cholera outbreak in the Central Plateau of Haiti. These samples underwent whole genome sequencing and subsequent metagenomic analysis to characterize the microbial community of bacteria, fungi, protists, and viruses, and to identify antibiotic resistance and virulence associated genes. Replicates from sites were analyzed by principle components analysis, and distinct genomic profiles were obtained for each site. Cholera toxin converting phage was detected at one site, and Shiga toxin converting phages at several sites. Members of the Acinetobacter family were frequently detected in samples, including members implicated in waterborne diseases. These results indicate a metagenomic approach to evaluating water samples can be useful for source tracking and the surveillance of pathogens such as Vibrio cholerae over time, as well as for monitoring virulence factors such as cholera toxin.

A Game-Theoretic Model of Cholera with Optimal Personal Protection Strategies

Cholera is an acute gastro-intestinal infection that affects millions of people throughout the world each year, primarily but not exclusively in developing countries. Because of its public health ramifications, considerable mathematical attention has been paid to the disease. Here we consider one neglected aspect of combating cholera: personal participation in anti-cholera interventions. We construct a game-theoretic model of cholera in which individuals choose whether to participate in either vaccination or clean water consumption programs under assumed costs. We find that relying upon individual compliance significantly lowers the incidence of the disease as long as the cost of intervention is sufficiently low, but does not eliminate it. The relative costs of the measures determined whether a population preferentially adopts a single preventative measure or employs the measure with the strongest early adoption.

Development of a Field Laboratory for Monitoring of Fecal-Sludge Treatment Plants

In urban humanitarian-aid operations, safe treatment of fecal sludge is highly important. While currently field-deployable fecal-sludge treatment plants are being developed, field-ready analytical equipment for process-control and public health monitoring is missing. Within the Microbial Sludge Quality project, a field laboratory was developed. A minimum set of parameters for the considered processes was developed through literature research. The analytical methods were tested on their field applicability and, if necessary, modified. The following methods were modified for field use: bacteriological analysis (sample homogenization and counting), chemical oxygen demand (sample digestion), volatile fatty acid–alkalinity titration (redesigned test setup), total solids (redesigned test setup), and ammonia determination (redesigned test setup). For bacteriological analysis, chemical oxygen demand, and total solids the modifications lead to highly comparable analytical results. The results obtained by the field methodology for volatile fatty acid–alkalinity titration and ammonia determination were sufficient for field-process monitoring; however, they did not correlate as well. To enable rapid startup of the laboratory during humanitarian-aid missions, it was developed to include analytical and support equipment. The usage of the developed laboratory should allow close-in-time process monitoring and public-health assessments of fecal-sludge treatment plants.

Cholera outbreak caused by drinking contaminated water from a lakeshore water-collection site, Kasese District, south-western Uganda, June-July 2015

On 20 June 2015, a cholera outbreak affecting more than 30 people was reported in a fishing village, Katwe, in Kasese District, south-western Uganda. We investigated this outbreak to identify the mode of transmission and to recommend control measures. We defined a suspected case as onset of acute watery diarrhoea between 1 June and 15 July 2015 in a resident of Katwe village; a confirmed case was a suspected case with Vibrio cholerae cultured from stool. For case finding, we reviewed medical records and actively searched for cases in the community. In a case-control investigation we compared exposure histories of 32 suspected case-persons and 128 age-matched controls. We also conducted an environmental assessment on how the exposures had occurred. We found 61 suspected cases (attack rate = 4.9/1000) during this outbreak, of which eight were confirmed. The primary case-person had onset on 16 June; afterwards cases sharply increased, peaked on 19 June, and rapidly declined afterwards. After 22 June, eight scattered cases occurred. The case-control investigation showed that 97% (31/32) of cases and 62% (79/128) of controls usually collected water from inside a water-collection site "X" (ORM-H = 16; 95% CI = 2.4-107). The primary case-person who developed symptoms while fishing, reportedly came ashore in the early morning hours on 17 June, and defecated "near" water-collection site X. We concluded that this cholera outbreak was caused by drinking lake water collected from inside the lakeshore water-collection site X. At our recommendations, the village administration provided water chlorination tablets to the villagers, issued water boiling advisory to the villagers, rigorously disinfected all patients' faeces and, three weeks later, fixed the tap-water system.

Near real-time forecasting for cholera decision making in Haiti after Hurricane Matthew

Computational models of cholera transmission can provide objective insights into the course of an ongoing epidemic and aid decision making on allocation of health care resources. However, models are typically designed, calibrated and interpreted post-hoc. Here, we report the efforts of a team from academia, field research and humanitarian organizations to model in near real-time the Haitian cholera outbreak after Hurricane Matthew in October 2016, to assess risk and to quantitatively estimate the efficacy of a then ongoing vaccination campaign. A rainfall-driven, spatially-explicit meta-community model of cholera transmission was coupled to a data assimilation scheme for computing short-term projections of the epidemic in near real-time. The model was used to forecast cholera incidence for the months after the passage of the hurricane (October-December 2016) and to predict the impact of a planned oral cholera vaccination campaign. Our first projection, from October 29 to December 31, predicted the highest incidence in the departments of Grande Anse and Sud, accounting for about 45% of the total cases in Haiti. The projection included a second peak in cholera incidence in early December largely driven by heavy rainfall forecasts, confirming the urgency for rapid intervention. A second projection (from November 12 to December 31) used updated rainfall forecasts to estimate that 835 cases would be averted by vaccinations in Grande Anse (90% Prediction Interval [PI] 476-1284) and 995 in Sud (90% PI 508-2043). The experience gained by this modeling effort shows that state-of-the-art computational modeling and data-assimilation methods can produce informative near real-time projections of cholera incidence. Collaboration among modelers and field epidemiologists is indispensable to gain fast access to field data and to translate model results into operational recommendations for emergency management during an outbreak. Future efforts should thus draw together multi-disciplinary teams to ensure model outputs are appropriately based, interpreted and communicated.

Planning for globally coordinated cessation of bivalent oral poliovirus vaccine: risks of non-synchronous cessation and unauthorized oral poliovirus vaccine use

BACKGROUND

Oral polio vaccine (OPV) containing attenuated serotype 2 polioviruses was globally withdrawn in 2016, and bivalent OPV (bOPV) containing attenuated serotype 1 and 3 polioviruses needs to be withdrawn after the certification of eradication of all wild polioviruses to eliminate future risks from vaccine-derived polioviruses (VDPVs). To minimize risks from VDPVs, the planning and implementation of bOPV withdrawal should build on the experience with withdrawing OPV containing serotype 2 polioviruses while taking into account similarities and differences between the three poliovirus serotypes.

METHODS

We explored the risks from (i) a failure to synchronize OPV cessation and (ii) unauthorized post-cessation OPV use for serotypes 1 and 3 in the context of globally-coordinated future bOPV cessation and compared the results to similar analyses for serotype 2 OPV cessation.

RESULTS

While the risks associated with a failure to synchronize cessation and unauthorized post-cessation OPV use appear to be substantially lower for serotype 3 polioviruses than for serotype 2 polioviruses, the risks for serotype 1 appear similar to those for serotype 2. Increasing population immunity to serotype 1 and 3 poliovirus transmission using pre-cessation bOPV supplemental immunization activities and inactivated poliovirus vaccine in routine immunization reduces the risks of circulating VDPVs associated with non-synchronized cessation or unauthorized OPV use.

CONCLUSIONS

The Global Polio Eradication Initiative should synchronize global bOPV cessation during a similar window of time as occurred for the global cessation of OPV containing serotype 2 polioviruses and should rigorously verify the absence of bOPV in immunization systems after its cessation.

Characterization of Interventional Studies of the Cholera Epidemic in Haiti

In October 2010, the Haitian Ministry of Public Health and Population (MSPP; Port au Prince, Haiti) reported a cholera epidemic caused by contamination of the Artibonite River by a United Nation Stabilization Mission camp. Interventional studies of the subsequent responses, including a descriptive Methods section and systematic approach, may be useful in facilitating comparisons and applying lessons learned to future outbreaks. The purpose of this study was to examine publicly available documents relating to the 2010 cholera outbreak to answer: (1) What information is publicly available on interventional studies conducted during the epidemic, and what was/were the impact(s)? and (2) Can the interventions be compared, and what lessons can be learned from their comparison? A PubMed (National Center for Biotechnology Information, National Institutes of Health; Bethesda, Maryland USA) search was conducted using the parameters "Haiti" and "cholera." Studies were categorized as "interventional research," "epidemiological research," or "other." A distinction was made between studies and narrative reports. The PubMed search yielded 171 papers, 59 (34.0%) of which were epidemiological and 12 (7.0%) were interventional studies. The remaining 100 papers (59.0%) comprised largely of narrative, anecdotal descriptions. An expanded examination of publications by the World Health Organization (WHO; Geneva, Switzerland), the Center for Research in the Epidemiology of Disasters (CRED; Brussels, Belgium), United States Agency for International Development (USAID; Washington, DC USA)-Development Experience Clearinghouse (DEC), and US National Library of Medicine's (NLM; Bethesda, Maryland USA) Disaster Literature databases yielded no additional interventional studies. The unstructured formats and differing levels of detail prohibited comparisons between interventions, even between those with a similar approach. Only two (17.0%) interventional studies included any impact data, although neither commented whether the intervention improved health or reduced incidence or mortality related to cholera. Agreed frameworks for guiding responses and subsequent reporting are needed to ensure reports contain sufficient detail to draw conclusions for the definition of best practices and for the design of future interventions. Miller J , Birnbaum ML . Characterization of interventional studies of the cholera epidemic in Haiti. Prehosp Disaster Med. 2018;33(2):176-181.

John Snow, Cholera, the Broad Street Pump; Waterborne Diseases Then and Now

Cholera was a major global scourge in the 19^th century, with frequent large-scale epidemics in European cities primarily originating in the Indian subcontinent. John Snow conducted pioneering investigations on cholera epidemics in England and particularly in London in 1854 in which he demonstrated that contaminated water was the key source of the epidemics. His thorough investigation of an epidemic in the Soho district of London led to his conclusion that contaminated water from the Broad Street pump was the source of the disease and, consequently, the removal of the handle led to cessation of the epidemic. He further studied cholera in London homes that were receiving water from two water supply systems; one from the sewage contaminated portion of the Thames River and the other that drew its water upstream from an uncontaminated part of the river. Rates of infection among clients of the distribution system drawing contaminated water far exceeded the, rates among those served by the company whose water intake was from above the contaminated section of the river. This demonstration reinforced the goals of the sanitation movement, which developed sewage drainage systems and water purification systems in cities and towns in the following decades, therewith vastly reducing the threats of cholera, typhoid and many other waterborne diseases. Despite progress being made globally, the public health problems of waterborne disease, including cholera, are by no means gone today, even in high-income countries. The tragic introduction of cholera after the earthquake devastation in Haiti in 2010 resulted in many thousands of cases and deaths from cholera indicating the still-present dangers of diseases spread into disaster situations. Cholera and other waterborne diseases remain some of the heaviest burdens of disease and death in low-income countries, especially after natural disasters or warfare as in Yemen in 2017 and are continuing challenges for global health.

Analyzing the response to epidemics: concept of evidence-based Haddon matrix

Purpose

The purpose of this paper is to propose a novel evidence-based Haddon matrix that identifies intervention options for organizations and governments responding to an epidemic in a developing economy.

Design/methodology/approach

A literature review of articles published within a year of the cholera outbreak in Haiti. Two separate types of literature sources are used – academic and non-academic – to apprehend the value and role of interventions implemented and/or identified.

Findings

The Haddon matrix helps break down the challenges involved in the containment of an epidemic into smaller, manageable components. This research shows that the matrix enables visualization of past evidence, help dissect various informational sources, and increase collaboration across humanitarian organizations. It will also serve as a building block for academics to identify new research directions to respond to epidemic outbreaks.

Research limitations/implications

The analysis focuses on the cholera epidemic in Haiti. Future work will be directed to generalize the identified recommendations and insights to a broader context.

Originality/value

This paper presents an evidence-based Haddon matrix that infers recommendations and insights based on past evidence for each phase (pre-event, response, and post-event) and factor (agent, host, physical environment, and socio-cultural environment) of an epidemic and for various stakeholders (humanitarian organizations, governments, and academics). The matrix provides a structured framework to identify interventions and best practices to address challenges during an epidemic outbreak.

Public health implications of complex emergencies and natural disasters

Background

During the last decade, conflict or natural disasters have displaced unprecedented numbers of persons. This leads to conditions prone to outbreaks that imperil the health of displaced persons and threaten global health security. Past literature has minimally examined the association of communicable disease outbreaks with complex emergencies (CEs) and natural disasters (NDs).

Methods

To examine this association, we identified CEs and NDs using publicly available datasets from the Center for Research on the Epidemiology of Disasters and United Nations Flash and Consolidated Appeals archive for 2005–2014. We identified outbreaks from World Health Organization archives. We compared findings to identify overlap of outbreaks, including their types (whether or not of a vaccine-preventable disease), and emergency event types (CE, ND, or Both) by country and year using descriptive statistics and measure of association.

Results

There were 167 CEs, 912 NDs, 118 events linked to ‘Both’ types of emergencies, and 384 outbreaks. Of CEs, 43% were associated with an outbreak; 24% NDs were associated with an outbreak; and 36% of ‘Both’ types of emergencies were associated with an outbreak. Africa was disproportionately affected, where 67% of total CEs, 67% of ‘Both’ events (CE and ND), and 46% of all outbreaks occurred for the study period. The odds ratio of a vaccine-preventable outbreak occurring in a CE versus an ND was 4.14 (95% confidence limits 1.9, 9.4).

Conclusions

CEs had greater odds of being associated with outbreaks compared with NDs. Moreover, CEs had high odds of a vaccine-preventable disease causing that outbreak. Focusing on better vaccine coverage could reduce CE-associated morbidity and mortality by preventing outbreaks from spreading.

Mathematical models for predicting human mobility in the context of infectious disease spread: introducing the impedance model

Background

Mathematical models of human mobility have demonstrated a great potential for infectious disease epidemiology in contexts of data scarcity. While the commonly used gravity model involves parameter tuning and is thus difficult to implement without reference data, the more recent radiation model based on population densities is parameter-free, but biased. In this study we introduce the new impedance model, by analogy with electricity. Previous research has compared models on the basis of a few specific available spatial patterns. In this study, we use a systematic simulation-based approach to assess the performances.

Methods

Five hundred spatial patterns were generated using various area sizes and location coordinates. Model performances were evaluated based on these patterns. For simulated data, comparison measures were average root mean square error (aRMSE) and bias criteria. Modeling of the 2010 Haiti cholera epidemic with a basic susceptible–infected–recovered (SIR) framework allowed an empirical evaluation through assessing the goodness-of-fit of the observed epidemic curve.

Results

The new, parameter-free impedance model outperformed previous models on simulated data according to average aRMSE and bias criteria. The impedance model achieved better performances with heterogeneous population densities and small destination populations. As a proof of concept, the basic compartmental SIR framework was used to confirm the results obtained with the impedance model in predicting the spread of cholera in Haiti in 2010.

Conclusions

The proposed new impedance model provides accurate estimations of human mobility, especially when the population distribution is highly heterogeneous. This model can therefore help to achieve more accurate predictions of disease spread in the context of an epidemic.

Electronic supplementary material

The online version of this article (10.1186/s12942-017-0115-7) contains supplementary material, which is available to authorized users.

Staying Alive: Vibrio cholerae's Cycle of Environmental Survival, Transmission, and Dissemination

Infectious diseases kill nearly 9 million people annually. Bacterial pathogens are responsible for a large proportion of these diseases, and the bacterial agents of pneumonia, diarrhea, and tuberculosis are leading causes of death and disability worldwide. Increasingly, the crucial role of nonhost environments in the life cycle of bacterial pathogens is being recognized. Heightened scrutiny has been given to the biological processes impacting pathogen dissemination and survival in the natural environment, because these processes are essential for the transmission of pathogenic bacteria to new hosts. This chapter focuses on the model environmental pathogen Vibrio cholerae to describe recent advances in our understanding of how pathogens survive between hosts and to highlight the processes necessary to support the cycle of environmental survival, transmission, and dissemination. We describe the physiological and molecular responses of V. cholerae to changing environmental conditions, focusing on its survival in aquatic reservoirs between hosts and its entry into and exit from human hosts.

Characterization of Vibrio cholerae O1 strains that trace the origin of Haitian-like genetic traits

Vibrio cholerae O1 is the etiological agent of the severe diarrheal disease cholera. The bacterium has recently been causing outbreaks in Haiti with catastrophic effects. Numerous mutations have been reported in V. cholerae O1 strains associated with the Haitian outbreak. These mutations encompass among other the genes encoding virulence factors such as the pilin subunit of the toxin-co-regulated pilus (tcpA), cholera toxin B subunit (ctxB), repeat in toxins (rtxA), and other genes such as the quinolone resistance-determining region (QRDR) of gyrase A (gyrA), rstB of RS element along with the alteration in the number of repeat sequences at the promoter region of ctxAB. Given the numerous genetic changes in those Haitian isolates, we decided to investigate the possible origins of those variations in the Indian subcontinent. Thus, we determined the genetic traits among V. cholerae O1 strains in Delhi, India. A total of 175 strains isolated from cholera patients during 2004 to 2012 were analysed in the present study. Our results showed that all the tested strains carried Haitian type tcpA (tcpA^CIRS) and variant gyrA indicating their first appearance before 2004 in Delhi. The Haitian variant rtxA and ctxB7 were first detected in Delhi during 2004 and 2006, respectively. Interestingly, not a single strain with the combination of El Tor rtxA and ctxB7 was detected in this study. The Delhi strains carried four heptad repeats (TTTTGAT) in the CT promoter region whereas Haitian strains carried 5 such repeats. Delhi strains did not have any deletion mutations in the rstB like Haitian strains. Overall, our study demonstrates the sequential accumulation of Haitian-like genetic traits among V. cholerae O1 strains in Delhi at different time points prior to the Haitian cholera outbreak.

Forensic Approaches to Detect Possible Agents of Bioterror

Many biological agents have been strategic pathogenic agents throughout history. Some have even changed history as a consequence of early discoveries of their use as weapons of war. Many of these bioagents can be easily isolated from the environment, and some have recently been genetically manipulated to become more pathogenic for biowarfare. However, it is difficult to determine accidental outbreaks of disease from intentional exposures. In this review, we examine how molecular tools have been used in combination with forensic research to resolve cases of unusual outbreaks and trace the source of the biocrime. New technologies are also discussed in terms of their crucial role impacting forensic science. The anthrax event of 2001 serves as an example of the real threat of bioterrorism and the employment of bioagents as weapons against a population. The Amerithrax investigation has given us lessons of the highest resolution possible with new technologies capable of distinguishing isolates at the base-pair level of sensitivity. In addition, we discuss the implications of proper sanitation to avoid waterborne diseases. The use of new methods in forensic science and health-related surveillance will be invaluable in determining the source of any new disease outbreak, and these data will allow for a quick response to any type of public health threat, whether accidental or purposely initiated.

Global stability and uniform persistence of the reaction-convection-diffusion cholera epidemic model

We study the global stability issue of the reaction-convection-diffusion cholera epidemic PDE model and show that the basic reproduction number serves as a threshold parameter that predicts whether cholera will persist or become globally extinct. Specifically, when the basic reproduction number is beneath one, we show that the disease-free-equilibrium is globally attractive. On the other hand, when the basic reproduction number exceeds one, if the infectious hosts or the concentration of bacteria in the contaminated water are not initially identically zero, we prove the uniform persistence result and that there exists at least one positive steady state.

A REACTION–DIFFUSION MODEL FOR THE CONTROL OF CHOLERA EPIDEMIC

Understanding the spatio-temporal dynamics of cholera outbreaks may help in devising more effective control procedures. In this paper, we have considered a reaction–diffusion system for biological control of cholera epidemic. Firstly, we have focused on temporal evolution of cholera in a region and its control using lytic bacteriophage in the aquatic reservoirs. Then, we have explored the effect of spatial dispersion of populations on the disease dynamics. We have observed the onset of sustained oscillations via Hopf-bifurcation for the endemic state of temporal system. This onset of fluctuations in populations depends upon the phage adsorption rate. But in the spatially extended setting, all the populations stabilize i.e., the spatio-temporal distribution of all the populations becomes uniform. Some numerical computations have been done to verify analytical results.

Mortality Rates during Cholera Epidemic, Haiti, 2010-2011

Actual rates were higher than rates calculated from healthcare facility reports.

The 2010 cholera epidemic in Haiti was one of the largest cholera epidemics ever recorded. To estimate the magnitude of the death toll during the first wave of the epidemic, we retrospectively conducted surveys at 4 sites in the northern part of Haiti. Overall, 70,903 participants were included; at all sites, the crude mortality rates (19.1–35.4 deaths/1,000 person-years) were higher than the expected baseline mortality rate for Haiti (9 deaths/1,000 person-years). This finding represents an excess of 3,406 deaths (2.9-fold increase) for the 4.4% of the Haiti population covered by these surveys, suggesting a substantially higher cholera mortality rate than previously reported.

Phenotypic and genetic characteristics of Vibrio cholerae O1 carrying Haitian ctxB and attributes of classical and El Tor biotypes isolated from Silvassa, India

Vibrio cholerae O1 biotype El Tor, the causative agent of the seventh pandemic, has recently been replaced by strains carrying classical and Haitian ctxB in India, Haiti and other parts of the world. We conducted phenotypic and genetic tests to characterize V. cholerae O1 isolated between 2012 and 2014 from Silvassa, India, to examine the presence of virulence and regulatory genes, seventh pandemic marker, ctxB type and biofilm formation and to study genomic diversity. Of the 59 V. cholerae O1, eight isolates belong to El Tor prototype, one to classical prototype and the remaining isolates have attributes of both classical and El Tor biotypes. PCR and ctxB gene sequencing revealed the presence of classical ctxB in four strains and Haitian ctxB in 55 isolates; indicating that isolates were either an El Tor or hybrid variant. All isolates carried virulence, regulatory, adherence, Vibrio seventh pandemic pathogenicity island I and seventh pandemic group-specific marker VC2346, in addition to tcpAET and rstRET, the features of seventh pandemic strains, and produced cholera toxin and biofilm. PFGE analysis showed that the majority of isolates are clonal and belong to fingerprint pattern A; however, pattern B is unrelated and patterns C and D are distinct, suggesting considerable diversity in the genomic content among them. These data thus show that isolates from Silvassa are genetically diverse and that Haitian ctxB and hybrid phenotypes are undergoing global dissemination.

Improving health in the Arctic region through safe and affordable access to household running water and sewer services: an Arctic Council initiative

Important health disparities have been documented among the peoples of the Arctic and subarctic, including those related to limited access to in-home improved drinking water and sanitation services. Although improving water, sanitation and hygiene (WASH) has been a focus of the United Nations for decades, the Arctic region has received little attention in this regard. A growing body of evidence highlights inequalities across the region for the availability of in-home drinking WASH services and for health indicators associated with these services. In this review, we highlight relevant data and describe an initiative through the Arctic Council's Sustainable Development Working Group to characterize the extent of WASH services in Arctic nations, the related health indicators and climate-related vulnerabilities to WASH services. With this as a baseline, efforts to build collaborations across the Arctic will be undertaken to promote innovations that can extend the benefits of water and sanitation services to all residents.

The inclusion of international migrants in Brazilian healthcare system policies: the case of Haitians in the state of Amazonas

Resumo A partir do enfoque etnográfico sobre as redes sociais articuladas em torno da questão do imigrante no Amazonas, o artigo reflete sobre como o Sistema Único de Saúde (SUS) respondeu às demandas colocadas por um contingente inesperado de novos usuários, tendo em vista os princípios doutrinários que lhe dão sustentação, especialmente o da equidade. O foco é a onda de imigração haitiana rumo ao Brasil, iniciada em fevereiro de 2010 pelos estados fronteiriços da região Norte: Acre, Rondônia e Amazonas, concentrando-se neste último, descrevendo alguns aspectos do período mais crítico da imigração (entre março de 2010 e março de 2012) e sua recepção pelo SUS.

Disease and disaster: Optimal deployment of epidemic control facilities in a spatially heterogeneous population with changing behaviour

Epidemics of water-borne infections often follow natural disasters and extreme weather events that disrupt water management processes. The impact of such epidemics may be reduced by deployment of transmission control facilities such as clinics or decontamination plants. Here we use a relatively simple mathematical model to examine how demographic and environmental heterogeneities, population behaviour, and behavioural change in response to the provision of facilities, combine to determine the optimal configurations of limited numbers of facilities to reduce epidemic size, and endemic prevalence. We show that, if the presence of control facilities does not affect behaviour, a good general rule for responsive deployment to minimise epidemic size is to place them in exactly the locations where they will directly benefit the most people. However, if infected people change their behaviour to seek out treatment then the deployment of facilities offering treatment can lead to complex effects that are difficult to foresee. So careful mathematical analysis is the only way to get a handle on the optimal deployment. Behavioural changes in response to control facilities can also lead to critical facility numbers at which there is a radical change in the optimal configuration. So sequential improvement of a control strategy by adding facilities to an existing optimal configuration does not always produce another optimal configuration. We also show that the pre-emptive deployment of control facilities has conflicting effects. The configurations that minimise endemic prevalence are very different to those that minimise epidemic size. So cost-benefit analysis of strategies to manage endemic prevalence must factor in the frequency of extreme weather events and natural disasters.

Strategies to Prevent Cholera Introduction during International Personnel Deployments: A Computational Modeling Analysis Based on the 2010 Haiti Outbreak

BACKGROUND

Introduction of Vibrio cholerae to Haiti during the deployment of United Nations (UN) peacekeepers in 2010 resulted in one of the largest cholera epidemics of the modern era. Following the outbreak, a UN-commissioned independent panel recommended three pre-deployment intervention strategies to minimize the risk of cholera introduction in future peacekeeping operations: screening for V. cholerae carriage, administering prophylactic antimicrobial chemotherapies, or immunizing with oral cholera vaccines. However, uncertainty regarding the effectiveness of these approaches has forestalled their implementation by the UN. We assessed how the interventions would have impacted the likelihood of the Haiti cholera epidemic.

METHODS AND FINDINGS

We developed a stochastic model for cholera importation and transmission, fitted to reported cases during the first weeks of the 2010 outbreak in Haiti. Using this model, we estimated that diagnostic screening reduces the probability of cases occurring by 82% (95% credible interval: 75%, 85%); however, false-positive test outcomes may hamper this approach. Antimicrobial chemoprophylaxis at time of departure and oral cholera vaccination reduce the probability of cases by 50% (41%, 57%) and by up to 61% (58%, 63%), respectively. Chemoprophylaxis beginning 1 wk before departure confers a 91% (78%, 96%) reduction independently, and up to a 98% reduction (94%, 99%) if coupled with vaccination. These results are not sensitive to assumptions about the background cholera incidence rate in the endemic troop-sending country. Further research is needed to (1) validate the sensitivity and specificity of rapid test approaches for detecting asymptomatic carriage, (2) compare prophylactic efficacy across antimicrobial regimens, and (3) quantify the impact of oral cholera vaccine on transmission from asymptomatic carriers.

CONCLUSIONS

Screening, chemoprophylaxis, and vaccination are all effective strategies to prevent cholera introduction during large-scale personnel deployments such as that precipitating the 2010 Haiti outbreak. Antimicrobial chemoprophylaxis was estimated to provide the greatest protection at the lowest cost among the approaches recently evaluated by the UN.

Cholera Outbreak in Grande Comore: 1998-1999

In 1998, a cholera epidemic in east Africa reached the Comoros Islands, an archipelago in the Mozambique Channel that had not reported a cholera case for more than 20 years. In just a little over 1 year (between January 1998 and March 1999), Grande Comore, the largest island in the Union of the Comoros, reported 7,851 cases of cholera, about 3% of the population. Using case reports and field observations during the medical response, we describe the epidemiology of the 1998-1999 cholera epidemic in Grande Comore. Outbreaks of infectious diseases on islands provide a unique opportunity to study transmission dynamics in a nearly closed population, and they may serve as stepping-stones for human pathogens to cross unpopulated expanses of ocean.

The impact of spatial arrangements on epidemic disease dynamics and intervention strategies

The role of spatial arrangements on the spread and management strategies of a cholera epidemic is investigated. We consider the effect of human and pathogen movement on optimal vaccination strategies. A metapopulation model is used, incorporating a susceptible-infected-recovered system of differential equations coupled with an equation modelling the concentration of Vibrio cholerae in an aquatic reservoir. The model compared spatial arrangements and varying scenarios to draw conclusions on how to effectively manage outbreaks. The work is motivated by the 2010 cholera outbreak in Haiti. Results give guidance for vaccination strategies in response to an outbreak.

Tracking Cholera through Surveillance of Oral Rehydration Solution Sales at Pharmacies: Insights from Urban Bangladesh

Background

In Bangladesh, pharmacy-purchased oral rehydration solution (ORS) is often used to treat diarrhea, including cholera. Over-the-counter sales have been used for epidemiologic surveillance in the past, but rarely, if ever, in low-income countries. With few early indicators for cholera outbreaks in endemic areas, diarrhea-related product sales may serve as a useful surveillance tool.

Methodology/Principal Findings

We tracked daily ORS sales at 50 pharmacies and drug-sellers in an urban Bangladesh community of 129,000 for 6-months while simultaneously conducting surveillance for diarrhea hospitalizations among residents. We developed a mobile phone based system to track the sales of ORS and deployed it in parallel with a paper-based system. Our objectives were to determine if the mobile phone system was practical and acceptable to pharmacists and drug sellers, whether data were reported accurately compared to a paper-based system, and whether ORS sales were associated with future incidence of cholera hospitalizations within the community. We recorded 47,215 customers purchasing ORS, and 315 hospitalized diarrhea cases, 22% of which had culture-confirmed cholera. ORS sales and diarrhea incidence were independently associated with the mean daily temperature; therefore both unadjusted and adjusted models were explored. Through unadjusted cross-correlation statistics and generalized linear models, we found increases in ORS sales were significantly associated with increases in hospitalized diarrhea cases up to 9-days later and hospitalized cholera cases up to one day later. After adjusting for mean daily temperature, ORS was significantly associated with hospitalized diarrhea two days later and hospitalized cholera one day later.

Conclusions/Significance

Pharmacy sales data may serve as a feasible and useful surveillance tool. Given the relatively short lagged correlation between ORS sales and diarrhea, rapid and accurate sales data are key. More work is needed in creating actionable algorithms that make use of this data and in understanding the generalizability of our findings to other settings.

In Bangladesh, people often purchase oral rehydration solution (ORS) at their neighborhood pharmacy to treat diarrhea, including cholera. Over-the-counter sales have been used for epidemiologic surveillance, but rarely in low-income countries. With few early indicators for cholera outbreaks in endemic areas, diarrhea-related product sales may be a useful surveillance tool. We tracked daily ORS sales at pharmacies and drug-sellers in an urban Bangladesh community with both a mobile phone and paper-based system while conducting surveillance for diarrhea hospitalizations among residents. We found that increases in ORS sales were significantly associated increases in hospitalized diarrhea cases up to two days later and hospitalized cholera cases up to one day later. Our findings suggest that surveillance systems based on over-the-counter product sales may be a feasible and useful way to detect outbreaks in low-income settings and that mobile technology may make it even easier to collect implement.

High-resolution spatial analysis of cholera patients reported in Artibonite department, Haiti in 2010-2011

BACKGROUND

Cholera is caused by Vibrio cholerae, and is transmitted through fecal-oral contact. Infection occurs after the ingestion of the bacteria and is usually asymptomatic. In a minority of cases, it causes acute diarrhea and vomiting, which can lead to potentially fatal severe dehydration, especially in the absence of appropriate medical care. Immunity occurs after infection and typically lasts 6-36 months. Cholera is responsible for outbreaks in many African and Asian developing countries, and caused localised and episodic epidemics in South America until the early 1990s. Haiti, despite its low socioeconomic status and poor sanitation, had never reported cholera before the recent outbreak that started in October 2010, with over 720,000 cases and over 8700 deaths (Case fatality rate: 1.2%) through 8 december 2014. So far, this outbreak has seen 3 epidemic peaks, and it is expected that cholera will remain in Haiti for some time.

METHODOLOGY/FINDINGS

To trace the path of the early epidemic and to identify hot spots and potential transmission hubs during peaks, we examined the spatial distribution of cholera patients during the first two peaks in Artibonite, the second-most populous department of Haiti. We extracted the geographic origin of 84,000 patients treated in local health facilities between October 2010 and December 2011 and mapped these addresses to 63 rural communal sections and 9 urban cities. Spatial and cluster analysis showed that during the first peak, cholera spread along the Artibonite River and the main roads, and sub-communal attack rates ranged from 0.1% to 10.7%. During the second peak, remote mountain areas were most affected, although sometimes to very different degrees even in closely neighboring locations. Sub-communal attack rates during the second peak ranged from 0.2% to 13.7%. The relative risks at the sub-communal level during the second phase showed an inverse pattern compared to the first phase.

CONCLUSION/SIGNIFICANCE

These findings demonstrate the value of high-resolution mapping for pinpointing locations most affected by cholera, and in the future could help prioritize the places in need of interventions such as improvement of sanitation and vaccination. The findings also describe spatio-temporal transmission patterns of the epidemic in a cholera-naïve country such as Haiti. By identifying transmission hubs, it is possible to target prevention strategies that, over time, could reduce transmission of the disease and eventually eliminate cholera in Haiti.

Survival, induction and resuscitation of Vibrio cholerae from the viable but non-culturable state in the Southern Caribbean Sea

The causative agent of cholera, Vibrio cholerae, can enter into a viable but non-culturable (VBNC) state in response to unfavorable conditions. The aim of this study was to evaluate the in situ survival of V. cholerae in an aquatic environment of the Southern Caribbean Sea, and its induction and resuscitation from the VBNC state. V. cholerae non-O1, non-O139 was inoculated into diffusion chambers placed at the Cuare Wildlife Refuge, Venezuela, and monitored for plate, total and viable cells counts. At 119 days of exposure to the environment, the colony count was < 10 CFU/mL and a portion of the bacterial population entered the VBNC state. Additionally, the viability decreased two orders of magnitude and morphological changes occurred from rod to coccoid cells. Among the aquatic environmental variables, the salinity had negative correlation with the colony counts in the dry season. Resuscitation studies showed significant recovery of cell cultivability with spent media addition (p < 0.05). These results suggest that V. cholerae can persist in the VBNC state in this Caribbean environment and revert to a cultivable form under favorable conditions. The VBNC state might represent a critical step in cholera transmission in susceptible areas.

Household-level spatiotemporal patterns of incidence of cholera, Haiti, 2011

A cholera outbreak began in Haiti during October, 2010. Spatiotemporal patterns of household-level cholera in Ouest Department showed that the initial clusters tended to follow major roadways; subsequent clusters occurred further inland. Our data highlight transmission pathway complexities and the need for case and household-level analysis to understand disease spread and optimize interventions.

Global burden of childhood diarrhea and interventions

PURPOSE OF REVIEW

Diarrhea is a leading cause of morbidity and mortality among children under 5 years in low-income and middle-income countries. Over the past 2 decades under-five mortality has decreased substantially, but reductions have been uneven and unsatisfactory in resource-poor regions.

RECENT FINDINGS

There are known interventions which can prevent diarrhea or manage children who suffer from it. Interventions with proven effectiveness at the prevention level include water, sanitation, and hygiene interventions, breastfeeding, complementary feeding, vitamin A and zinc supplementation, and vaccines for diarrhea (rotavirus and cholera). Oral rehydration solution, zinc treatment, continued feeding, and antibiotic treatment for certain strains of diarrhea (cholera, Shigella, and cryptosporidiosis) are effective strategies for treatment of diarrhea. The recent Lancet series using the 'Lives Saved' tool suggested that if these identified interventions were scaled up to a global coverage to at least 80%, and immunizations to at least 90%; almost all deaths due to diarrhea could be averted.

SUMMARY

The current childhood mortality burden highlights the need of a focused global diarrhea action plan. The findings suggest that with proper packaging of interventions and delivery platforms, the burden of childhood diarrhea can be reduced to a greater extent. All that is required is greater attention and steps toward right direction.