Understanding the cholera epidemic, Haiti

Genomic insights into the 2022-2023Vibrio cholerae outbreak in Malawi

Malawi experienced its deadliest Vibrio cholerae (Vc) outbreak following devastating cyclones, with >58,000 cases and >1700 deaths reported between March 2022 and May 2023. Here, we use population genomics to investigate the attributes and origin of the Malawi 2022-2023 Vc outbreak isolates. Our results demonstrate the predominance of ST69 clone, also known as the seventh cholera pandemic El Tor (7PET) lineage, expressing O1 Ogawa (~ 80%) serotype followed by Inaba (~ 16%) and sporadic non-O1/non-7PET serogroups (~ 4%). Phylogenetic reconstruction revealed that the Malawi outbreak strains correspond to a recent importation from Asia into Africa (sublineage AFR15). These isolates harboured known antimicrobial resistance and virulence elements, notably the ICEGEN/ICEVchHai1/ICEVchind5 SXT/R391-like integrative conjugative elements and a CTXφ prophage with the ctxB7 genotype compared to historical Malawian Vc isolates. These data suggest that the devastating cyclones coupled with the recent importation of 7PET serogroup O1 strains, may explain the magnitude of the 2022-2023 cholera outbreak in Malawi.

Informing policy via dynamic models: Cholera in Haiti

Public health decisions must be made about when and how to implement interventions to control an infectious disease epidemic. These decisions should be informed by data on the epidemic as well as current understanding about the transmission dynamics. Such decisions can be posed as statistical questions about scientifically motivated dynamic models. Thus, we encounter the methodological task of building credible, data-informed decisions based on stochastic, partially observed, nonlinear dynamic models. This necessitates addressing the tradeoff between biological fidelity and model simplicity, and the reality of misspecification for models at all levels of complexity. We assess current methodological approaches to these issues via a case study of the 2010-2019 cholera epidemic in Haiti. We consider three dynamic models developed by expert teams to advise on vaccination policies. We evaluate previous methods used for fitting these models, and we demonstrate modified data analysis strategies leading to improved statistical fit. Specifically, we present approaches for diagnosing model misspecification and the consequent development of improved models. Additionally, we demonstrate the utility of recent advances in likelihood maximization for high-dimensional nonlinear dynamic models, enabling likelihood-based inference for spatiotemporal incidence data using this class of models. Our workflow is reproducible and extendable, facilitating future investigations of this disease system.

The paradoxes of Mycobacterium tuberculosis molecular evolution and consequences for the inference of tuberculosis emergence date

The date of Mycobacterium tuberculosis complex emergence has been the subject of long debates. New studies joining archaeological efforts with sequencing methods raise high hopes for solving whether this emergence is closer to 70,000 or to 6000 years before present. Inferring the date of emergence of this pathogen based on sequence data requires a molecular clock. Several clocks inferred from different types of loci and/or different samples, using both sound reasoning and reliable data, are actually very different, which we refer to as the paradoxes of M. tuberculosis molecular evolution. After having presented these paradoxes, we will remind the limits of the molecular clocks used in the different studies such as the assumption of homogeneous substitution rate. We will then review recent results that shed new light on the characteristics of M. tuberculosis molecular evolution: traces of diverse selection pressures, the impact of host dynamics, etc. We provide some ideas on what to do next to get nearer to a reliable dating of Mycobacterium tuberculosis complex emergence. Among them, the collection of additional remains from ancient tuberculosis seems still essential.

Ancestral Origin and Dissemination Dynamics of Reemerging Toxigenic Vibrio cholerae, Haiti

The 2010 cholera epidemic in Haiti was thought to have ended in 2019, and the Prime Minister of Haiti declared the country cholera-free in February 2022. On September 25, 2022, cholera cases were again identified in Port-au-Prince. We compared genomic data from 42 clinical Vibrio cholerae strains from 2022 with data from 327 other strains from Haiti and 1,824 strains collected worldwide. The 2022 isolates were homogeneous and closely related to clinical and environmental strains circulating in Haiti during 2012-2019. Bayesian hypothesis testing indicated that the 2022 clinical isolates shared their most recent common ancestor with an environmental lineage circulating in Haiti in July 2018. Our findings strongly suggest that toxigenic V. cholerae O1 can persist for years in aquatic environmental reservoirs and ignite new outbreaks. These results highlight the urgent need for improved public health infrastructure and possible periodic vaccination campaigns to maintain population immunity against V. cholerae.

Notional Spread of Cholera in Haiti Following a Natural Disaster: Considerations for Military and Disaster Relief Personnel

INTRODUCTION

Cholera remains a significant public health threat for many countries, and the severity largely varies by the population and local conditions that drive disease spread, especially in endemic areas prone to natural disasters and flooding. Epidemiological models can provide useful information to military planners for understanding disease spread within populations and the effectiveness of response options for preventing the transmission among deployed and stationed personnel. This study demonstrates the use of epidemiological modeling to understand the dynamics of cholera transmission to inform emergency planning and military preparedness in areas with highly communicable diseases.

MATERIALS AND METHODS

Areas with higher probability for a potential cholera outbreak in Haiti followed by a natural disaster were identified. The hotspots were then used to seed an extended compartmental model, EpiGrid, to simulate notional spread scenarios of cholera originating in three distinct areas in Haiti. Disease parameters were derived from the 2010 cholera outbreak in Haiti, and disease spread was simulated over a 12-week period under uncontrolled and controlled spread.

RESULTS

For each model location, scenarios of mitigated (intervention with 30% transmission reduction via international aid) and unmitigated (without intervention) are simulated. The results depict the geographical spread and estimate the cumulative cholera infection for each notional scenario over the course of 3 months. Disease transmission differs considerably across origin site with an outbreak originating in the department of Nippes spanning the largest geographic area and resulting in the largest number of cumulative cases after 12 weeks under unmitigated (79,518 cases) and mitigated (35,667 cases) spread scenarios.

CONCLUSIONS

We modeled the notional re-emergence and spread of cholera following the August 2021 earthquake in Haiti while in the midst of the global COVID-19 pandemic. This information can help guide military and emergency response decision-making during an infectious disease outbreak and considerations for protecting military personnel in the midst of a humanitarian response. Military planners should consider the use of epidemiological models to assess the health risk posed to deployed and stationed personnel in high-risk areas.

Application of electric field treatment (EFT) for microbial control in water and liquid food

Water disinfection and food pasteurization are critical to reducing waterborne and foodborne diseases, which have been a pressing public health issue globally. Electrified treatment processes are emerging and have become promising alternatives due to the low cost of electricity, independence of chemicals, and low potential to form by-products. Electric field treatment (EFT) is a physical pathogen inactivation approach, which damages cell membrane by irreversible electroporation. EFT has been studied for both water disinfection and food pasteurization. However, no study has systematically connected the two fields with an up-to-date review. In this article, we first provide a comprehensive background of microbial control in water and food, followed by the introduction of EFT. Subsequently, we summarize the recent EFT studies for pathogen inactivation from three aspects, the processing parameters, its efficacy against different pathogens, and the impact of liquid properties on the inactivation performance. We also review the development of novel configurations and materials for EFT devices to address the current challenges of EFT. This review introduces EFT from an engineering perspective and may serve as a bridge to connect the field of environmental engineering and food science.

What Whole Genome Sequencing Has Told Us About Pathogenic Vibrios

When the first microbial genome sequences were published just 20 years ago, our understanding regarding the microbial world changed dramatically. The genomes of the first pathogenic vibrios sequenced, including Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus revealed a functional and phylogenetic diversity previously unimagined as well as a genome structure indelibly shaped by horizontal gene transfer. The initial glimpses into these organisms also revealed a genomic plasticity that allowed these bacteria to thrive in challenging and varied aquatic and marine environments, but critically also a suite of pathogenicity attributes. In this review we outline how our understanding of vibrios has changed over the last two decades with the advent of genomics and advances in bioinformatic and data analysis techniques, it has become possible to provide a more cohesive understanding regarding these bacteria: how these pathogens have evolved and emerged from environmental sources, their evolutionary routes through time and space, how they interact with other bacteria and the human host, as well as initiate disease. We outline novel approaches to the use of whole genome sequencing for this important group of bacteria and how new sequencing technologies may be applied to study these organisms in future studies.

Environmental Reservoirs of Pathogenic Vibrio spp. and Their Role in Disease: The List Keeps Expanding

Vibrio species are natural inhabitants of aquatic environments and have complex interactions with the environment that drive the evolution of traits contributing to their survival. These traits may also contribute to their ability to invade or colonize animal and human hosts. In this review, we attempt to summarize the relationships of Vibrio spp. with other organisms in the aquatic environment and discuss how these interactions could potentially impact colonization of animal and human hosts.

The Impact of Earthquakes on Public Health: A Narrative Review of Infectious Diseases in the Post-Disaster Period Aiming to Disaster Risk Reduction

Earthquakes are among the most impressive natural phenomena with very high potential to set off a chain of effects that significantly affects public health through casualties and injuries. Related disasters are attributed not only to the strong ground motion and coseismic phenomena but also to secondary effects, comprising mainly landslides and tsunamis, among others. All these can create harsh conditions favorable for the emergence of infectious diseases that are capable of causing additional human and economic losses and disruption of the emergency and recovery process. The present study comprises an extensive narrative review of the existing literature on the earthquake-triggered infectious diseases recorded worldwide, along with their symptoms, causative pathogens, associated risk factors, most vulnerable population groups, and prevention strategies. Respiratory, gastrointestinal, and vector-borne diseases, as well as wound and skin infections, are mainly recorded among the earthquake-affected population. Measures for effectively preventing earthquake-triggered infectious diseases are also proposed. One of the widely proposed measures is the establishment of a proper disease surveillance system in order to immediately and effectively identify the pre- and post-disaster occurrence of infectious diseases. This approach significantly contributes to disease trends monitoring, validation of early warning, and support of the emergency response and recovery actions.

Foreign intervention following a humanitarian crisis: help versus harm

Recent experience of humanitarian and disaster relief efforts have demonstrated the critical importance of the local health infrastructure and its response to a disaster in both the short and long term. With increasing involvement of Foreign Medical Teams (FMT), both military and civilian, in these relief efforts, there is a necessity to review how best a FMT can involve and develop the local response; it is no longer valid to design an intervention insular from the local population. Key themes found in interventions that have damaged the local infrastructure and response include: bypassing, undermining and overstretching local capacities; poaching local staff; aid-fuelled inflation; lack of accountability; developing an intervention that the local population is incapable of providing once the FMT has gone and using the local infrastructure for service delivery for the FMT. Principles written by the Organisation for Economic Co-operation and Development summarise concepts that can be used when designing an intervention so as to avoid damaging the local response and their infrastructure. They focus on involving the local population, understanding the complexities and history of the area and the requirement to develop and instil resilience to future crises.

[Management of the COVID-19 epidemic in the carrier battle group (January-April 2020) by the Armed Forces Epidemiology and Public Health Center]

Objectives

Faced with the COVID-19 epidemic that occurred within the naval air group and the nuclear aircraft carrier Charles de Gaulle, the French Armed Forces Epidemiology and Public Health Center (CESPA) carried out an investigation (January - April 2020) whose objectives were: to identify the possible routes of introduction of the virus ; to describe the characteristics of the epidemic and to describe and model the dynamics of the epidemic's spread.

Methods

A telephone survey was conducted. The biological diagnoses were transmitted by the medical antennas. A time/place/population analysis was carried out, as well as the description of the clinical pictures with their exposure factors. The instantaneous reproduction rate Rt of the epidemic was modeled. A spatial analysis of the epidemic on board was carried out. Forty-three viral genomes were sequenced and compared to the reference bases.

Results

0f 1767 sailors, 1568 (89%) participated in the telephone survey and 1064 (67.9%) were confirmed cases. Four patient profiles have been described: asymptomatic (13.0%); non-specific symptomatic (8.1%); specific symptomatic (76.3%); severe cases (2.6%). In univariate and multivariate analysis, age, overweight and obesity were significantly associated with the risk of having a severe form. Smoking was a protective factor. The evolution kinetics of Rt was in favor of an introduction of the virus at the end of February with a reintroduction during the stopover in Brest. Analysis of viral genomes ruled out introduction and spread of a single strain.

Conclusion

Despite the control measures taken, an epidemic occurred. The often pauci-symptomatic clinical pictures resulted in a delay in identification. CESPA was able to carry out this epidemiological investigation within a highly constrained timeframe, showing all the interest of its integrated public health model.

Implementing Online Discussion and Mind Mapping to Investigate a Disease Outbreak

The recent increase in online learning modalities due to coronavirus disease 2019 (COVID-19) has created a significant gap in real-time discussions on complex issues. This lack of enrichment from student discussions levies the concern of a deficiency in strong learning outcomes. This learning activity focused on mind mapping to facilitate small group discussions on the 2010 cholera outbreak in Haiti. Students learned about the disease triangle and cause-and-effect relationships on a large spatial and temporal scale. In this case, the three points of the triangle represented the pathogen (Vibrio cholerae), the environment (Haiti), and the hosts (Haitians). Each student in each small group was required to read a unique article to present to their group on the day of the activity. Using mind mapping, each group illustrated relationships that may have exacerbated the cholera outbreak. Learning outcomes were assessed through the evaluation of questions relevant to that week's exercise. Students were assessed on their ability to recognize relationships between the pathogen, environment, and hosts, as well as the ability to apply what they learned to the present-day COVID-19 pandemic. The disease triangle activity is readily accessible and can be easily implemented for identifying cause-and-effect relationships in large-scale systems. Importantly, this learning activity retained real-time discussion-based problem-solving for improving students' critical thinking skills and approaches to complex issues.

SARS-CoV-2 Transmission in the Military during the Early Phase of the Pandemic-A Systematic Analysis

Militaries worldwide have been affected by COVID-19 pandemic. However, the impact and epidemiological characteristics of transmission during the early phase of the pandemic is not well-studied. This study aims to systematically estimate the baseline incidence of COVID-19 in the military worldwide and identify the potential risk factors of transmission and clinical characteristics of the cases. English and Chinese literature reporting COVID-19 cases in military worldwide published on four electronic databases (PubMed, Scopus, EMBASE, and CKNI) through 28 May 2021 were systematically screened and synthesized qualitatively. Forty-six studies involving at least 711,408 military personnel in 17 countries were synthesized. Low incidence of cases was observed in the military with pooled COVID-19 incidence of 0.19% (95%CI: 0.00–9.18%). We observed a higher incidence among those (1) with overseas exposure (39.85%; 95%CI: 0.00–95.87%) rather than local exposure (3.03%; 95%CI: 0.00–12.53%), (2) who were on either local/overseas military deployment (26.78%; 95%CI: 0.00–71.51%) as compared to those not deployed (4.37%; 95%CI: 0.00–17.93%), and (3) on overseas military deployment (39.84%; 95%CI: 0.00–95.87%) as compared to local military deployment (3.03%; 95%CI: 2.37–3.74%). The majority of the cases were symptomatic (77.90% (95%CI: 43.91–100.00%)); hospitalization and mortality rates were low at 4.43% (95%CI: 0.00–25.34%) and 0.25% (95%CI: 0.00–0.85%), respectively; and headache, anosmia, ageusia, myalgia, nasal congestion, and cough were the most commonly observed symptoms. Overseas and local deployment were observed to have higher risk of SARS-CoV-2 transmission. Sustainable, active SARS-CoV-2 surveillance strategies are crucial to detect and contain transmission early during military deployments.

Cholera in Haiti

The cholera epidemic that hit Haiti from October 2010 to February 2019 was the world's deadliest of the last 25 years. Officially, the successive waves caused 9789 deaths, although numerous additional casualties could not be recorded. The origin of this epidemic has been the subject of a controversy involving two opposing theories. The first hypothesis, put forward by renowned American academics, was that the cholera epidemic originated from the environment, due to the proliferation and transmission of aquatic Vibrio cholerae bacteria driven by a confluence of circumstances, i.e., the earthquake followed by a hot summer and, ultimately, heavy rainfall and flooding. The alternative hypothesis, which was subsequently confirmed by epidemiological and genomic studies, attributed the epidemic to the recent importation of cholera by UN peacekeepers having recently arriving from Nepal, and to a river polluted with sewage. In late 2016, the Secretary General of the United Nations finally begged the Haitian people for forgiveness. This implicit recognition of the role of the UN in the cholera epidemic helped to fund the ongoing fight against it. Case-area targeted interventions aimed at interrupting cholera transmission were reinforced, which resulted in the extinction of the epidemic within two years. In the meantime, several phylogenetic studies on Vibrio cholerae during the seventh cholera pandemic demonstrated that local environmental and global epidemic Vibrio populations were distinct. These studies also showed that epidemics arose when the bacterium had diversified and that it had spread during transmission events associated with human travel.

Investigation of a COVID-19 outbreak on the Charles de Gaulle aircraft carrier, March to April 2020: a retrospective cohort study

Background

SARS-CoV-2 emergence was a threat for armed forces. A COVID-19 outbreak occurred on the French aircraft carrier Charles de Gaulle from mid-March to mid-April 2020.

Aim

To understand how the virus was introduced, circulated then stopped circulation, risk factors for infection and severity, and effectiveness of preventive measures.

Methods

We considered the entire crew as a cohort and collected personal, clinical, biological, and epidemiological data. We performed viral genome sequencing and searched for SARS-CoV-2 in the environment.

Results

The attack rate was 65% (1,148/1,767); 1,568 (89%) were included. The male:female ratio was 6.9, and median age was 29 years (IQR: 24–36). We examined four clinical profiles: asymptomatic (13.0%), non-specific symptomatic (8.1%), specific symptomatic (76.3%), and severe (i.e. requiring oxygen therapy, 2.6%). Active smoking was not associated with severe COVID-19; age and obesity were risk factors. The instantaneous reproduction rate (R_t) and viral sequencing suggested several introductions of the virus with 4 of 5 introduced strains from within France, with an acceleration of R_t when lifting preventive measures. Physical distancing prevented infection (adjusted OR: 0.55; 95% CI: 0.40–0.76). Transmission may have stopped when the proportion of infected personnel was large enough to prevent circulation (65%; 95% CI: 62–68).

Conclusion

Non-specific clinical pictures of COVID-19 delayed detection of the outbreak. The lack of an isolation ward made it difficult to manage transmission; the outbreak spread until a protective threshold was reached. Physical distancing was effective when applied. Early surveillance with adapted prevention measures should prevent such an outbreak.

Seismic Resilience of Rural Water Supply Systems; Factor Analysis of Cases Set in Sichuan Province, China

The seismic resilience of water supply systems can be impacted by numerous factors, but what these factors are in the rural context of China is unknown. In this study, 41 potential influencing factors of seismic-resilience for rural water supply system (RWSS) were obtained through a literature review and semi-structured expert interview, comprising 26 general influencing factors (GFs) and 15 water supply safety influencing factors (SFs). This study verified and ranked these factors through a questionnaire survey delivered to RWSS stakeholders in Sichuan Province, China. Based on 123 valid, returned questionnaires, these factors are divided into 9 factor groups through factor analysis performed on GFs and SFs, respectively, of which “economic resilience” and “organizational resilience in disaster prevention stage” are shown to be the most important factor groups. Additionally, it found that the experience of earthquake events significantly affects the perceptions of stakeholders on the importance of certain factors. Specifically, stakeholders who have experienced an earthquake prioritize the post-earthquake resilience of the system, while those who have not experienced an earthquake prioritize the absorption capacity of the system in the disaster prevention stage. Thus, it is not appropriate to use fixed weights to evaluate the seismic resilience of RWSSs. Significantly, this outcome differs from existing findings on the resilience of Urban Water Supply Systems (UWSSs), where “technical resilience” is the key dimension. These findings can help decision-makers fully understand the factors affecting the seismic resilience of RWSSs in China, and in doing so, augment the strengthening of rural water supply.

Assay for Evaluating the Abundance of Vibrio cholerae and Its O1 Serogroup Subpopulation from Water without DNA Extraction

Cholera is a severe diarrheal disease caused by Vibrio cholerae, a natural inhabitant of brackish water. Effective control of cholera outbreaks depends on prompt detection of the pathogen from clinical specimens and tracking its source in the environment. Although the epidemiology of cholera is well studied, rapid detection of V. cholerae remains a challenge, and data on its abundance in environmental sources are limited. Here, we describe a sensitive molecular quantification assay by qPCR, which can be used on-site in low-resource settings on water without the need for DNA extraction. This newly optimized method exhibited 100% specificity for total V. cholerae as well as V. cholerae O1 and allowed detection of as few as three target CFU per reaction. The limit of detection is as low as 5 × 10³ CFU/L of water after concentrating biomass from the sample. The ability to perform qPCR on water samples without DNA extraction, portable features of the equipment, stability of the reagents at 4 °C and user-friendly online software facilitate fast quantitative analysis of V. cholerae. These characteristics make this assay extremely useful for field research in resource-poor settings and could support continuous monitoring in cholera-endemic areas.

A three-staged framework for measuring water supply resilience in rural China based on PLS-SEM

China suffers from frequent large-scale earthquakes, posing a significant challenge to the development and integrity of its rural water supply system (RWSS). The earthquake resilience of water supply systems is understood to be a function of multifaceted factors, which are time- and space-dependent. Measuring the seismic-resilience of RWSS in China remains a challenge. This paper proposes a multi-stage comprehensive evaluation framework, focusing on the relationship between multi-dimensional factors and the seismic- resilience of RWSS in rural areas, across three stages: before, during and after earthquake events. This study comprises four steps: (1) Development of a multi-stage evaluation conceptual framework; (2) identification of seismic-resilience factors; (3) verification of the relationships between factors and stages; and (4) formation of the final evaluation framework. The relationship between multi-dimensional factors is confirmed by a method of triangulation through the quantitative analysis of PLS-SEM combined with the qualitative literature analysis, highlighting the causal approach of the resilience of RWSSs, so as to better understand the resilience state of each stage of disaster. Understanding these factors and their influence on the seismic capacity of RWSS will enable local authorities to recognize the existing advantages and disadvantages of these factors, so as to carry out better resilience practice in all stages of disasters.

Epidemicity of cholera spread and the fate of infection control measures

The fate of ongoing infectious disease outbreaks is predicted through reproduction numbers, defining the long-term establishment of the infection, and epidemicity indices, tackling the reactivity of the infectious pool to new contagions. Prognostic metrics of unfolding outbreaks are of particular importance when designing adaptive emergency interventions facing real-time assimilation of epidemiological evidence. Our aim here is twofold. First, we propose a novel form of the epidemicity index for the characterization of cholera epidemics in spatial models of disease spread. Second, we examine in hindsight the survey of infections, treatments and containment measures carried out for the now extinct 2010–2019 Haiti cholera outbreak, to suggest that magnitude and timing of non-pharmaceutical and vaccination interventions imply epidemiological responses recapped by the evolution of epidemicity indices. Achieving negative epidemicity greatly accelerates fading of infections and thus proves a worthwhile target of containment measures. We also show that, in our model, effective reproduction numbers and epidemicity indices are explicitly related. Therefore, providing an upper bound to the effective reproduction number (significantly lower than the unit threshold) warrants negative epidemicity and, in turn, a rapidly fading outbreak preventing coalescence of sparse local sub-threshold flare-ups.

Bio-safety and bio-security: A major global concern for ongoing COVID-19 pandemic

Besides its impacts on governance, economics, human culture, geostrategic partnership and environment, globalization greatly exerted control over science and security policies. Biosecurity is the critical job of efforts, policy and preparation to protect health of human, animal and environmental against any biological threats. With the transition into a global village, the possibility of biosecurity breaches has significantly increased. The COVID-19 pandemic is an example of an infringement on biosecurity that has posed a serious threat to the world. Since the first report on the recognition of COVID-19, a number of governments have taken preventive measures, like; lockdown, screening and early detection of suspected and implementing the required response to protect the loss of life and economy. Unfortunately, some of these measures have only recently been taken in some countries, which have contributed significantly to an increased morbidity and loss of life on a daily basis. In this article, the biological risks affecting human, animal and environmental conditions, biosafety violations and preventive measures have been discussed in order to reduce the outbreak and impacts of a pandemic like COVID-19.

Cholera outbreak caused by drinking unprotected well water contaminated with faeces from an open storm water drainage: Kampala City, Uganda, January 2019

Background

Kampala city slums, with one million dwellers living in poor sanitary conditions, frequently experience cholera outbreaks. On 6 January 2019, Rubaga Division notified the Uganda Ministry of Health of a suspected cholera outbreak in Sembule village. We investigated to identify the source and mode of transmission, and recommended evidence-based interventions.

Methods

We defined a suspected case as onset of profuse, painless, acute watery diarrhoea in a Kampala City resident (≥ 2 years) from 28 December 2018 to 11 February 2019. A confirmed case was a suspected case with Vibrio cholerae identified from the patient’s stool specimen by culture. We found cases by record review and active community case-finding. We conducted a case–control study in Sembule village, the epi-center of this outbreak, to compare exposures between confirmed case-persons and asymptomatic controls, individually matched by age group. We overlaid rainfall data with the epidemic curve to identify temporal patterns between rain and illnesses. We conducted an environmental assessment, interviewed village local council members, and tested water samples from randomly-selected households and water sources using culture and PCR to identify V. cholerae.

Results

We identified 50 suspected case-patients, with three deaths (case-fatality rate: 6.0%). Of 45 case-patients with stool samples tested, 22 were confirmed positive for V. cholerae O1, serotype Ogawa. All age groups were affected; persons aged 5–14 years had the highest attack rate (AR) (8.2/100,000). The epidemic curve showed several point-source outbreaks; cases repeatedly spiked immediately following rainfall. Sembule village had a token-operated water tap, which had broken down 1 month before the outbreak, forcing residents to obtain water from one of three wells (Wells A, B, C) or a public tap. Environmental assessment showed that residents emptied their feces into a drainage channel connected to Well C. Drinking water from Well C was associated with illness (OR_M–H = 21, 95% CI 4.6–93). Drinking water from a public tap (OR_M–H = 0.07, 95% CI 0.014–0.304) was protective. Water from a container in one of eight households sampled tested positive for V. cholerae; water from Well C had coliform counts ˃ 900/100 ml.

Conclusions

Drinking contaminated water from an unprotected well was associated with this cholera outbreak. We recommended emergency chlorination of drinking water, fixing the broken token tap, and closure of Well C.

Variants of ctxB alleles of Vibrio cholerae O1 caused sequential cholera outbreaks in the tribal areas of Odisha, India

Cholera localized outbreaks/epidemics accounting for high morbidity and mortality have been reported in different years both from the coastal and tribal districts of Odisha. In the present study, the emergence and spread of two sequential cholera outbreaks reported in July to October 2012 from Rayagada and Kalahandi districts of Odisha was investigated. Environmental water samples from different sources and rectal swabs from diarrhoea patients were analysed for identification, antibiogram profiles and molecular studies using DMAMA-PCR assays. The pulsed field gel electrophoresis (PFGE) was done on some selected Vibrio cholerae O1 strains isolated from these cholera outbreak areas. Results showed 42% of rectal swabs and 2.3% of water samples collected from both the districts were positive for Vibrio cholerae O1 Ogawa biotype El Tor carrying both ctxB1 and ctxB7 genotypes. The common resistance profile of V. cholerae O1 strains was ampicillin, nalidixic acid, furazolidone and co-trimoxazole. The PFGE analysis on selected V. cholerae O1 strains of ctxB1 and ctxB7 genotypes showed three pulsotypes with 96% similarity matrix exhibiting the relationship with their respective water sources. Hence, continuous surveillance is highly essential to monitor the antibiogram profile and changing pattern of ctxB genotypes of V. cholerae O1 in this region.

Toward Cholera Elimination, Haiti

This study describes the apparent discontinuation of cholera transmission in Haiti since February 2019. Because vulnerabilities persist and vaccination remains limited, our findings suggest that case-area targeted interventions conducted by rapid response teams played a key role. We question the presence of environmental reservoirs in Haiti and discuss progress toward elimination.

"Y no quedó nada, nada de la casa, todo salió volando" (And there was nothing left, nothing of the house, everything flew away): a critical medical ecological perspective on the lived experience of hurricane María in Puerto Rico

Background

Ecological disasters create dramatic changes as man-made and natural ecosystems adapt to their effects. In 2017, Hurricanes Irma and María devastated Puerto Rico. Public focus after such traumatic ecological events often neglects pre-existing community dynamics, heterogeneity of lived experience, and complexity of decision-making in the disaster context. We intended to better understand the lived experience of this ecological trauma in communities across ecosystems in Puerto Rico and among those displaced to Florida.

Method

We used the Critical Medical Ecological (CME) framework to assess the relative contribution of ecological dimensions on lived experience across community levels and time. We used qualitative methods with emic coding and etic mapping of salient constructs to the ecological model. In total, 96 people participated in 23 discussion encounters. Two people coded interviews in Spanish using Dedoose. We identified common themes in sequential order mapped to elements of the CME to approximate the participants’ temporal experience.

Results

Codes applied to the period of the hurricane’s landfall, traverse, and exit were markedly distinct from the other two periods (before and after) examined in this study: the experience of the hurricane’s strike was highly personal and, at this level, reflected a mix of sociocultural, biological, and abiotic factors. After the hurricanes, social and community factors re-emerged while new risks and conditions arose that were biological (e.g., leptospirosis, no food or water) or abiotic (e.g., unusable roads/bridges, structures destroyed), but created ongoing stressors and social needs for communities. As we found, the dynamics of the social and household landscape sometimes involved the decision to leave Puerto Rico altogether, or forced people to continually face and adapt to the ongoing collapse in basic services that were only slowly and differentially restored.

Conclusion

Lived experience across each stage of the hurricanes differed substantially from one another. Communities disrupted by ecological disaster are also frequently entangled within global economic and political histories and dependencies that could preclude recovery. Island nations are especially vulnerable to both climate-induced ecological change and political-economic exploitation. The ongoing health effect of the hurricane remains palpable in many communities of Puerto Rico and among the diaspora in Florida.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-11847-w.

Virulence of Cholera Toxin Gene-Positive Vibrio cholerae Non-O1/non-O139 Strains Isolated From Environmental Water in Kolkata, India

Cholera toxin (CT)-producing Vibrio cholerae O1 and O139 cause acute diarrheal disease and are proven etiological agents of cholera epidemics and pandemics. On the other hand, V. cholerae non-O1/non-O139 are designated as non-agglutinable (NAG) vibrios and are not associated with epidemic cholera. The majority of NAG vibrios do not possess the gene for CT (ctx). In this study, we isolated three NAG strains (strains No. 1, 2, and 3) with ctx from pond water in Kolkata, India, and examined their pathogenic properties. The enterotoxicity of the three NAG strains in vivo was examined using the rabbit ileal intestinal loop test. Strain No. 1 induced the accumulation of fluid in the loop, and the volume of fluid was reduced by simultaneous administration of anti-CT antiserum into the loop. The volume of fluid in the loop caused by strains No. 2 and 3 was small and undetectable, respectively. Then, we cultured these three strains in liquid medium in vitro at two temperatures, 25°C and 37°C, and examined the amount of CT accumulated in the culture supernatant. CT was accumulated in the culture supernatant of strain No.1 when the strain was cultured at 25°C, but that was low when cultured at 37°C. The CT amount accumulated in the culture supernatants of the No. 2 and No. 3 strains was extremely low at both temperature under culture conditions examined. In order to clarify the virulence properties of these strains, genome sequences of the three strains were analyzed. The analysis showed that there was no noticeable difference among three isolates both in the genes for virulence factors and regulatory genes of ctx. However, vibrio seventh pandemic island-II (VSP-II) was retained in strain No. 1, but not in strains No. 2 or 3. Furthermore, it was revealed that the genotype of the B subunit of CT in strain No. 1 was type 1 and those of strains No. 2 and 3 were type 8. Histopathological examination showed the disappearance of villi in intestinal tissue exposed to strain No. 1. In addition, fluid accumulated in the loop due to the action of strain No. 1 had hemolytic activity. This indicated that strain No. 1 may possesses virulence factors to induce severe syndrome when the strain infects humans, and that some strains of NAG vibrio inhabiting pond water in Kolkata have already acquired virulence, which can cause illness in humans. There is a possibility that these virulent NAG vibrios, which have acquired genes encoding factors involved in virulence of V. cholerae O1, may emerge in various parts of the world and cause epidemics in the future.

The global dissemination of bacterial infections necessitates the study of reverse genomic epidemiology

Whole genome sequencing (WGS) has revolutionized the genotyping of bacterial pathogens and is expected to become the new gold standard for tracing the transmissions of bacterial infectious diseases for public health purposes. Traditional genomic epidemiology often uses WGS as a verification tool, namely, when a common source or epidemiological link is suspected, the collected isolates are sequenced for the determination of clonal relationships. However, increasingly frequent international travel and food transportation, and the associated potential for the cross-border transmission of bacterial pathogens, often lead to an absence of information on bacterial transmission routes. Here we introduce the concept of 'reverse genomic epidemiology', i.e. when isolates are inspected by genome comparisons to be sufficiently similar to one another, they are assumed to be a consequence of infection from a common source. Through BacWGSTdb (http://bacdb.org/BacWGSTdb/), a database we have developed for bacterial genome typing and source tracking, we have found that almost the entire analyzed 20 bacterial species exhibit the phenomenon of cross-border clonal dissemination. Five networks were further identified in which isolates sharing nearly identical genomes were collected from at least five different countries. Three of these have been documented as real infectious disease outbreaks, therefore demonstrating the feasibility and authority of reverse genomic epidemiology. Our survey and proposed strategy would be of potential value in establishing a global surveillance system for tracing bacterial transmissions and outbreaks; the related database and techniques require urgent standardization.

Control strategies to improve the low water quality of Souk-Ahras city

This work reports control strategies of the water quality in the city of Souk-Ahras (east Algeria). With the recent development, rapid population growth, and the consequences of climate change, the capacity of water supply reserves becomes more unpredictable in the long term. This has drastically affected the distributed water quantity. A correlation between bacteriological water analysis and the analysis of pollution indicative physicochemical parameters is developed to replace the slow bacteriological analysis, which takes more than two days, by directly accessible physicochemical analysis to anticipate the case-onset of waterborne diseases. A good correlation is found between different combinations of physicochemical pollution parameters: (Turbidity, Nitrates); (Turbidity, Active chlorine) (nitrates, active chlorine); (Ammonium, Chlorine) and (Turbidity, Ammonium) with Spearman rank coefficients of 0.8657, -0.8602 and -0.8531 -0.8227 et 0.7957 respectively. Besides, long term analysis (over several years) revealed a high correlation of more than 0.92 between the analysis of pollution indicative physicochemical parameters and bacteriological analysis. The EPANET software is used to simulate the hydraulic behaviour of the network system over an extended period within pressurized and pressure-deficient conditions. The simulation results of several supply scenarios of daily drinking water pressure in the city center area show that 62% of drinking water distribution system is supplied with a steep slope (80 m), 10% with unsatisfactory pressure and only 23% with acceptable pressure (1–80 m).

Therefore, the high working pressure at the mesh, and the interruptions of the water supply are factors that can lead to the occurrence of cross-connection cases. This diagnosis of the defects in the water supply system is combined with a statistical data analysis of physicochemical parameters to set up an effective sampling strategy that takes into account the frequency of analysis and the areas at risk to prevent the risk of waterborne diseases.

Active support after natural disasters: a review of a microbiologist's role

In the aftermath of a natural disaster, multispecialty rapid response teams are deployed to support health-related relief work. Microbiologists are often part of such teams, along with public health specialists, clinicians and entomologists, and can contribute to the response in multiple ways. The role of a microbiologist is critical not only for laboratory diagnosis of infectious diseases, but also for situational analysis and evaluation, planning, prevention and control. The task begins with risk assessment, specifically for identification of diseases epidemic and endemic to the area. Evaluation of existing laboratory setups and establishment of services where none exist is a priority, including facilitation of a tiered laboratory system. Training of laboratory staff at short notice in field settings, biosafety and biomedical waste management are niche areas where microbiologists can contribute. Emerging focus areas include establishment of modular laboratories, infection prevention and control in community evacuation centres and considerations for reopening of healthcare facilities closed due to extensive natural damage. A trained and efficient microbiologist will prove a valuable asset to provide timely and useful support for infectious disease diagnosis, prevention, control and management in the wake of natural disasters.

Delineating and Analyzing Locality-Level Determinants of Cholera, Haiti

Centre Department, Haiti, was the origin of a major cholera epidemic during 2010–2019. Although no fine-scale spatial delineation is officially available, we aimed to analyze determinants of cholera at the local level and identify priority localities in need of interventions. After estimating the likely boundaries of 1,730 localities by using Voronoi polygons, we mapped 5,322 suspected cholera cases reported during January 2015–September 2016 by locality alongside environmental and socioeconomic variables. A hierarchical clustering on principal components highlighted 2 classes with high cholera risk: localities close to rivers and unimproved water sources (standardized incidence ratio 1.71, 95% CI 1.02–2.87; p = 0.04) and urban localities with markets (standardized incidence ratio 1.69, 95% CI 1.25–2.29; p = 0.0006). Our analyses helped identify and characterize areas where efforts should be focused to reduce vulnerability to cholera and other waterborne diseases; these methods could be used in other contexts.

Decades of cholera in Odisha, India (1993-2015): lessons learned and the ways forward

Cholera is one of the major public health problems in the state of Odisha, India since centuries. The current paper is a comprehensive report on epidemiology of cholera in Odisha, which was documented from 1993. PubMed and Web of Knowledge were searched for publications reporting cholera in Odisha during the period 1993–2015. The search was performed using the keywords ‘Odisha’ and/or ‘Orissa’ and ‘Cholera’. In addition, manual search was undertaken to find out relevant papers. During the study period, a total of 37 cholera outbreaks were reported with an average of >1.5 cholera outbreaks per year and case fatality ratio was 0.3%. Vibrio cholerae O1 Ogawa serotype was the major causative agent in most of the cholera cases. The recent studies demonstrated the prevalence of V. cholerae O1, El Tor variants carrying ctxB1, ctxB7 and Haitian variant tcpA allele associated with polymyxin B sensitivity and these variants are replacing the proto type El Tor. The first report of variant ctxB7 in Odisha during super-cyclone 1999 predicted its emergence and subsequent spread causing cholera outbreaks. The prevalence of multidrug-resistant V. cholerae at different time periods created alarming situation. The efficacy trial of oral cholera vaccine (OCV, Shanchol) in a public health set-up in Odisha has shown encouraging results which should be deployed for community level vaccination among the vulnerable population. This paper has taken an effort to disseminate the valuable information of epidemiology of cholera that will influence the policy-makers and epidemiologists for constant surveillance in other parts of Odisha, India and around the globe.

Evolutionary Sweeps of Subviral Parasites and Their Phage Host Bring Unique Parasite Variants and Disappearance of a Phage CRISPR-Cas System

Vibrio cholerae is a significant threat to global public health in part due to its propensity for large-scale evolutionary sweeps where lineages emerge and are replaced. These sweeps may originate from the Bay of Bengal, where bacteriophage predation and the evolution of antiphage counterdefenses is a recurring theme. The bacteriophage ICP1 is a key predator of epidemic V. cholerae and is notable for acquiring a CRISPR-Cas system to combat PLE, a defensive subviral parasite encoded by its V. cholerae host. Here, we describe the discovery of four previously unknown PLE variants through a retrospective analysis of >3,000 publicly available sequences as well as one additional variant (PLE10) from recent surveillance of cholera patients in Bangladesh. In recent sampling we also observed a lineage sweep of PLE-negative V. cholerae occurring within the patient population in under a year. This shift coincided with a loss of ICP1's CRISPR-Cas system in favor of a previously prevalent PLE-targeting endonuclease called Odn. Interestingly, PLE10 was resistant to ICP1-encoded Odn, yet it was not found in any recent V. cholerae strains. We also identified isolates from within individual patient samples that revealed both mixed PLE(+)/PLE(-) V. cholerae populations and ICP1 strains possessing CRISPR-Cas or Odn with evidence of in situ recombination. These findings reinforce our understanding of the successive nature of V. cholerae evolution and suggest that ongoing surveillance of V. cholerae, ICP1, and PLE in Bangladesh is important for tracking genetic developments relevant to pandemic cholera that can occur over relatively short timescales. IMPORTANCE With 1 to 4 million estimated cases annually, cholera is a disease of serious global concern in regions where access to safe drinking water is limited by inadequate infrastructure, inequity, or natural disaster. The Global Task Force on Cholera Control (GTFCC.org) considers outbreak surveillance to be a primary pillar in the strategy to reduce mortality from cholera worldwide. Therefore, developing a better understanding of temporal evolutionary changes in the causative agent of cholera, Vibrio cholerae, could help in those efforts. The significance of our research is in tracking the genomic shifts that distinguish V. cholerae outbreaks, with specific attention paid to current and historical trends in the arms race between V. cholerae and a cooccurring viral (bacteriophage) predator. Here, we discover additional diversity of a specific phage defense system in epidemic V. cholerae and document the loss of a phage-encoded CRISPR-Cas system, underscoring the dynamic nature of microbial populations across cholera outbreaks.

'They came with cholera when they were tired of killing us with bullets': Community perceptions of the 2010 origin of Haiti's cholera epidemic

In 2010 following a catastrophic earthquake, Haiti saw the beginning of what would become the world's largest cholera epidemic. Nepalese United Nations peacekeepers were later implicated as the source of cholera. Our research examines Haitian community beliefs and perceptions, six-and-a-half years after the outbreak began, regarding the origin of Haiti's cholera outbreak. A narrative capture tool was used to record micronarratives of Haitian participants surrounding ten United Nations bases across Haiti. Seventy-seven micronarratives focused on cholera were selected for qualitative analysis from a larger dataset. Three themes emerged: who introduced cholera to Haiti, how cholera was introduced to Haiti, and preventative measures against cholera. With varying levels of confidence, the origins of the epidemic were conceptualised as directly resulting from the actions of the United Nations and Nepalese peacekeepers, exhibiting a distrust of foreign intervention in Haiti and frustration with inadequate water and sanitation infrastructure that facilitated widespread transmission of cholera. This study reinforces the need for additional transparent communication from the UN to address ongoing misconceptions surrounding the cholera outbreak, action to clean water and sanitation practices in Haiti, and for the voices of Haitian citizens to be heard and included in reforming foreign aid delivery in the country.

Retour d’expérience sur Covisan : un dispositif médicosocial pour casser les chaînes de transmission de la Covid-19

Covisan a été mis en place à partir du 14 avril 2020 au niveau de quatre sites pilotes de l’Assistance publique-Hôpitaux de Paris (APHP) pour casser les chaînes de transmission au SARS-CoV-2 selon un modèle original déjà éprouvé en Haïti pour éliminer le choléra dans les années 2010. Le dispositif consiste en un dépistage systématique des cas possibles de Covid-19, un accompagnement dans leur confinement et une prise en charge de leurs proches. Des équipes mobiles se sont déplacées au domicile des cas contacts afin d’évaluer les possibilités d’un isolement au domicile, de proposer des aides matérielles (courses, blanchisserie, hébergement externalisé) et de dépister leurs proches. Au 17 juin 2020, 6 376 patients ont été orientés vers Covisan, parmi lesquels 153 avaient une RT-PCR (reverse transciptase polymerase chain reaction) positive au SARSCoV-2. Covisan a permis un partenariat ville–hôpital innovant, en impliquant de multiples acteurs (personnels soignants, administratifs, logisticiens, métiers de service). Les autorités sanitaires se sont d’ailleurs inspirées de ce modèle pour lutter contre l’épidémie en mettant en place le contact tracing. Covisan, qui a appris en marchant, a également rencontré quelques difficultés, en particulier au niveau de la gestion des différents statuts des personnels ainsi qu’au niveau de la communication interne et externe.

Infections after Natural Disasters

Natural disasters, particularly flooding, are associated with many environmental changes, and the chances of infections after a disaster increase. Dead bodies are not associated with increased infections, but many other factors contribute to the increase in infections and possible outbreaks. This article discusses the factors associated with increased risk of infections and the types of infections that may occur after a natural disaster. This article also presents a brief discussion of infection prevention and mitigation after a natural disaster.

Humanitarian aid and local power structures: lessons from Haiti's 'shadow disaster'

This paper investigates the confluence of humanitarian aid, centralisation, and politics. The 7.0 magnitude earthquake in Haiti on 12 January 2010 led to more than USD 16 billion in pledges. By contrast, Hurricane Matthew, which made landfall in Haiti on 4 October 2016, stayed in the shadows, attracting about one per cent of the amount. While the earthquake exhibited one face of centralisation, the Category 4 storm laid bare rural vulnerabilities shaped by postcolonial state neglect, and reinforced by the influx of non-governmental organisations in the 'Republic of Port-au-Prince'. The study draws on data from four case studies in two departments to illuminate the legacies of hyper-centralisation in Haiti. Compounding matters, Matthew struck in the middle of an extended election that the international community attempted to control again. The paper argues that disaster assistance and politics are uncomfortably close, while reflecting on the momentary decentralisation of aid after the hurricane and its effectiveness.

Dissemination of Polymyxin B Sensitivity in El Tor Vibrio cholerae O1 Strains in Odisha, India

The Vibrio species undergo cryptic changes in their genetic material for better adaptability, which accounts for antibiotic resistance. In the present study, we investigated the emergence and spread of sensitivity to polymyxin B (PB) by El Tor V. cholerae O1 strains from 1995 to 2019 in Odisha, India. The results showed that out of 1200 V. cholerae O1 strains, 89.4% were resistant and the remaining 10.6% strains were sensitive to PB. The sensitivity to PB of V. cholerae O1 strains emerged from 2005 to 2019, except in 2015, clearly signifying the presence of classical biotype characteristics in the El Tor variant of V. cholerae O1 strains. The Etest assay revealed some interesting traits of PB susceptibility in the ctxB1 and ctxB7 genotypes of V. cholerae O1 strains. The minimum inhibitory concentration (MIC) of ctxB7 genotypes showed reduced MIC values of ≤ 4 µg/mL, whereas ctxB1 genotypes exhibited higher MIC values of 24 and 32 µg/mL.

Modelling the aqueous transport of an infectious pathogen in regional communities: application to the cholera outbreak in Haiti

A mathematical model is developed to describe the dynamics of the spread of a waterborne disease among communities located along a flowing waterway. The model is formulated as a system of reaction-diffusion-advection partial differential equations in this spatial setting. The compartments of the model consist of susceptible, infected, and recovered individuals in the communities along the waterway, together with a term representing the pathogen load in each community and a term representing the spatial concentration of pathogens flowing along the waterway. The model is applied to the cholera outbreak in Haiti in 2010.

Spatial and spatiotemporal clustering of the COVID-19 pandemic in Ecuador

Introduction: In Ecuador, the first COVID-19 case, the disease caused by the SARS-CoV-2 virus, was officially reported on February 29, 2020. As of April 2, the officially confirmed numbers of COVID-19 cases and deaths from it were 3 163 and 120, respectively, that is, a mortality rate of 3.8%. Objective: To identify spatial and spatiotemporal clusters of COVID-19 cases officially confirmed in Ecuador. Materials and methods: Case series study. An analysis of all COVID-19 cases officially confirmed in Ecuador from March 13, 2020 to April 2, 2020 was performed. Relative Risk (RR) of COVID-19 contagion was determined using the discrete Poisson distribution model in the SaTScan software. Clusters were generated using purely spatial and spatiotemporal scan statistics. Significance of each cluster was obtained through 999 iterations using the Monte Carlo simulation, obtaining the most probable random model. Results: As of April 2, spatiotemporal clustering allowed identifying two clusters in Ecuador, a main cluster in the Guayas province (area: 15 430 km2; population: 3.6 million inhabitants; RR: 7.08; p<0.000001; calculated annual incidence 1700 cases / 100 000 people) and a secondary cluster in the Pichincha province (area: 88 904 km2; population: 7.1 million; RR: 0.38; p<0.000001; calculated annual incidence 737 cases / 100 000 people.) Conclusions: The implementation of COVID-19 mitigation strategies should be focused on areas of high transmission risk; therefore, spatial, and spatiotemporal clustering with SaTScan can be extremely useful for the early detection and surveillance of COVID-19 outbreaks.

The Double-Edged Sword of Military Response to Societal Disruptions: A Systematic Review of the Evidence for Military Personnel as Pathogen Transmitters

Given their lack of immunity and increased exposure, military personnel have the potential to serve as carriers or reservoirs for infectious diseases into or out of the deployment areas, but, to our knowledge, the historical evidence for such transmission events has not previously been reviewed. Using PubMed, we performed a systematic review of published literature between 1955 and 2018, which documented evidence for military personnel transporting infectious pathogens into or out of deployment areas. Of the 439 articles screened, 67 were included for final qualitative and quantitative review. The data extracted from these articles described numerous instances in which thousands of military service members demonstrated potential or actual transmission and transportation of multiple diverse pathogens. These data underscore the immense importance preventive medical professionals play in mitigating such risk, how their public health efforts must be supported, and the importance of surveillance in protecting both military and civilian populations.

What are the drivers of recurrent cholera transmission in Nigeria? Evidence from a scoping review

BACKGROUND

The 2018 cholera outbreak in Nigeria affected over half of the states in the country, and was characterised by high attack and case fatality rates. The country continues to record cholera cases and related deaths to date. However, there is a dearth of evidence on context-specific drivers and their operational mechanisms in mediating recurrent cholera transmission in Nigeria. This study therefore aimed to fill this important research gap, with a view to informing the design and implementation of appropriate preventive and control measures.

METHODS

Four bibliographic literature sources (CINAHL (Plus with full text), Web of Science, Google Scholar and PubMed), and one journal (African Journals Online) were searched to retrieve documents relating to cholera transmission in Nigeria. Titles and abstracts of the identified documents were screened according to a predefined study protocol. Data extraction and bibliometric analysis of all eligible documents were conducted, which was followed by thematic and systematic analyses.

RESULTS

Forty-five documents met the inclusion criteria and were included in the final analysis. The majority of the documents were peer-reviewed journal articles (89%) and conducted predominantly in the context of cholera epidemics (64%). The narrative analysis indicates that social, biological, environmental and climatic, health systems, and a combination of two or more factors appear to drive cholera transmission in Nigeria. Regarding operational dynamics, a substantial number of the identified drivers appear to be functionally interdependent of each other.

CONCLUSION

The drivers of recurring cholera transmission in Nigeria are diverse but functionally interdependent; thus, underlining the importance of adopting a multi-sectoral approach for cholera prevention and control.

Toxigenic Vibrio cholerae evolution and establishment of reservoirs in aquatic ecosystems

The spread of cholera in the midst of an epidemic is largely driven by direct transmission from person to person, although it is well-recognized that Vibrio cholerae is also capable of growth and long-term survival in aquatic ecosystems. While prior studies have shown that aquatic reservoirs are important in the persistence of the disease on the Indian subcontinent, an epidemiological view postulating that locally evolving environmental V. cholerae contributes to outbreaks outside Asia remains debated. The single-source introduction of toxigenic V. cholerae O1 in Haiti, one of the largest outbreaks occurring this century, with 812,586 suspected cases and 9,606 deaths reported through July 2018, provided a unique opportunity to evaluate the role of aquatic reservoirs and assess bacterial transmission dynamics across environmental boundaries. To this end, we investigated the phylogeography of both clinical and aquatic toxigenic V. cholerae O1 isolates and show robust evidence of the establishment of aquatic reservoirs as well as ongoing evolution of V. cholerae isolates from aquatic sites. Novel environmental lineages emerged from sequential population bottlenecks, carrying mutations potentially involved in adaptation to the aquatic ecosystem. Based on such empirical data, we developed a mixed-transmission dynamic model of V. cholerae, where aquatic reservoirs actively contribute to genetic diversification and epidemic emergence, which underscores the complexity of transmission pathways in epidemics and endemic settings and the need for long-term investments in cholera control at both human and environmental levels.

Disaster preparedness to exotic and emerging infections

Exotic and emerging infectious diseases are emerging more frequently, and impacting more profoundly, all of humanity. Disasters risk reduction efforts over the preceding decades, culminating in the Hyogo and Sendai frameworks, have provided a roadmap for all countries to address emerging disaster related risks. Sudden onset or surprise epidemics of exotic or emerging diseases have the potential to exceed the adaptive capacity of countries and international efforts and lead to widespread unmitigated pandemics with severe flow on impacts. In this article pandemic preparedness is viewed through the lens of international disaster risk reduction and preparedness efforts. Preparing for the unknown or unexpected infectious disease crisis requires different approaches than the traditional approaches to disaster related epidemic events. Countries must be able to position themselves optimally through deliberate planning and preparation to a position where future exotic or emerging infections can be managed without overwhelming public health, and other societal resources.

Estimating effectiveness of case-area targeted response interventions against cholera in Haiti

Case-area targeted interventions (CATIs) against cholera are conducted by rapid response teams, and may include various activities like water, sanitation, hygiene measures. However, their real-world effectiveness has never been established. We conducted a retrospective observational study in 2015-2017 in the Centre department of Haiti. Using cholera cases, stool cultures and CATI records, we identified 238 outbreaks that were responded to. After adjusting for potential confounders, we found that a prompt response could reduce the number of accumulated cases by 76% (95% confidence interval, 59 to 86) and the outbreak duration by 61% (41 to 75) when compared to a delayed response. An intense response could reduce the number of accumulated cases by 59% (11 to 81) and the outbreak duration by 73% (49 to 86) when compared to a weaker response. These results suggest that prompt and repeated CATIs were significantly effective at mitigating and shortening cholera outbreaks in Haiti.

Burden of typhoid fever and cholera: similarities and differences. Prevention strategies for European travelers to endemic/epidemic areas

The burden of diarrheal diseases is very high, accounting for 1.7 to 5 billion cases per year worldwide. Typhoid fever (TF) and cholera are potentially life-threatening infectious diseases, and are mainly transmitted through the consumption of food, drink or water that have been contaminated by the feces or urine of subjects excreting the pathogen. TF is mainly caused by Salmonella typhi, whereas cholera is caused by intestinal infection by the toxin-producing bacterium Vibrio cholerae. These diseases typically affect low- and middle-income countries where housing is overcrowded and water and sanitation are poor, or where conflicts or natural disasters have led to the collapse of the water, sanitation and healthcare systems. Mortality is higher in children under 5 years of age. Regarding their geographical distribution, TF has a high incidence in sub-Saharan Africa, India and south-east Asia, while cholera has a high incidence in a few African countries, particularly in the Horn of Africa and the Arabian Peninsula. In the fight against these diseases, preventive measures are fundamental. With modern air travel, transmissible diseases can spread across continents and oceans in a few days, constituting a threat to global public health. Nowadays, people travel for many reasons, such as tourism and business. Several surveys have shown that a high proportion of travelers lack adequate information on safety issues, such as timely vaccination and prophylactic medications. The main objective of this overview is to provide information to help European travelers to stay healthy while abroad, and thus also to reduce the potential importation of these diseases and their consequent implications for public health and society. The preventive measures to be implemented in the case of travel to countries where these diseases are still endemic are well known: the adoption of safe practices and vaccinations. It is important to stress that an effective preventive strategy should be based both on vaccinations and on hygiene travel guidelines. Furthermore, the emergence of multidrug-resistant strains is becoming a serious problem in the clinical treatment of these diseases. For this reason, vaccination is the main solution.