Modeling Cholera Outbreaks

Chao, Dennis L.; Longini, Ira M.; Morris, J. Glenn

doi:10.1007/82_2013_307

Cited by 32 publications

(28 citation statements)

References 68 publications

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“…Thus, the model takes into account the current effect of an intervention (direct and indirect protection) and is an improvement over a classical static model. Unlike a model that simulates the transmission dynamics of cholera over time (e.g., ordinary differential equation models),38 a static model does not account for the future effect of the current intervention because the baseline incidence does not take into account the intervention applied in the previous year(s). However, our static model, like others,39,40 avoids having to estimate uncertain and unknown parameters required for dynamic models that explore the impact of multiple interventions introduced at various stages over time 41.…”

Section: Discussionmentioning

confidence: 99%

Modeling the Effect of Water, Sanitation, and Hygiene and Oral Cholera Vaccine Implementation in Haiti

Fung¹,

Fitter²,

Borse³

et al. 2013

The American Society of Tropical Medicine and Hygiene

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In 2010, toxigenic Vibrio cholerae was newly introduced to Haiti. Because resources are limited, decision-makers need to understand the effect of different preventive interventions. We built a static model to estimate the potential number of cholera cases averted through improvements in coverage in water, sanitation and hygiene (WASH) (i.e., latrines, point-of-use chlorination, and piped water), oral cholera vaccine (OCV), or a combination of both. We allowed indirect effects and non-linear relationships between effect and population coverage. Because there are limited incidence data for endemic cholera in Haiti, we estimated the incidence of cholera over 20 years in Haiti by using data from Malawi. Over the next two decades, scalable WASH interventions could avert 57,949–78,567 cholera cases, OCV could avert 38,569–77,636 cases, and interventions that combined WASH and OCV could avert 71,586–88,974 cases. Rate of implementation is the most influential variable, and combined approaches maximized the effect.

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Section: Discussionmentioning

confidence: 99%

Modeling the Effect of Water, Sanitation, and Hygiene and Oral Cholera Vaccine Implementation in Haiti

Fung¹,

Fitter²,

Borse³

et al. 2013

The American Society of Tropical Medicine and Hygiene

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“…In this study, we assessed the impact of five prospective oral cholera vaccination campaign scenarios as compared to a status quo scenario for a projected 10-year period in Haiti. Four independent modeling teams expanded on previously developed models of cholera transmission and vaccination interventions in Haiti 15,18,19,[21][22][23][24] to simulate the effects of mass vaccination campaigns of varying geographic scope, vaccination coverage, and rollout duration to assess the probability and time to elimination and the percentage of cases averted in each vaccination scenario. The aim of these analyses was to determine the feasibility of cholera elimination from Haiti in the status quo and through OCV use alone, and to inform ongoing policy discussions about the scope and rollout of potential OCV campaigns in Haiti in the near future.…”

Section: Introductionmentioning

confidence: 99%

Achieving coordinated national immunity and cholera elimination in Haiti through vaccination

Lee

Chao

Lemaitre

et al. 2019

Preprint

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Background Cholera was introduced into Haiti in 2010. Since, there have been over 820,000 reported cases and nearly 10,000 deaths. The year 2019 has seen the lowest reported number of cases since the epidemic began. Oral cholera vaccine (OCV) is safe and effective, but has generally not been seen as a primary tool for cholera elimination due to a limited period of protection and constrained supplies. Regionally, epidemic cholera is contained to the island of Hispaniola. Hence, Haiti may represent a unique opportunity to eliminate cholera by use of OCV. Methods We assess the probability of elimination and the potential health impact of OCV use in Haiti by leveraging simulations from four independent modeling teams. For a 10-year projection period, we compared the impact of five vaccination campaign scenarios, differing in geographic scope, vaccination coverage, and rollout duration to a status quo scenario without vaccination. Teams used common calibration data and assumptions for vaccine efficacy and vaccination scenarios, but all other model features and assumptions were determined independently. Findings A two-department OCV campaign proposed in Haiti's national plan for elimination had less than 50% probability of elimination across models, and only ambitious, nationwide campaigns had a high probability of reaching this goal. Despite their low probability of elimination, two-department campaigns averted a median of 13-58% of infections across models over the five years after the start of vaccination campaigns; a nationwide campaign implemented at the same coverage and rollout duration averted a median of 58-95% of infections across models. Interpretation Despite recent declines in cholera cases in Haiti, bold action is needed to promote elimination of cholera from the region. Large-scale cholera vaccination campaigns in Haiti offer the opportunity to synchronize nationwide immunity, providing near-term protection to the population while improvements to water and sanitation infrastructure create an environment favorable to long-term cholera elimination.

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“…Pathogens with \long cycle” transmission, like cholera, may be more affected by seasonal interruption than predicted from an SIR model, which captures short cycle (person-to-person) but not long cycle (environmental) transmission. Transmission models that include long cycle transmission could be used to study seasonality of enteric pathogens [6, 5, 9], while models that explicitly include vectors, such as [22], could be used to study vector-borne pathogens. However, the SIR model is sufficient for the qualitative analyses presented here.…”

Section: Discussionmentioning

confidence: 99%

Seasonality and the effectiveness of mass vaccination

Chao

Dimitrov

2016

Mathematical Biosciences and Engineering

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Many infectious diseases have seasonal outbreaks, which may be driven by cyclical environmental conditions (e.g., an annual rainy season) or human behavior (e.g., school calendars or seasonal migration). If a pathogen is only transmissible for a limited period of time each year, then seasonal outbreaks could infect fewer individuals than expected given the pathogen’s in-season transmissibility. Influenza, with its short serial interval and long season, probably spreads throughout a population until a substantial fraction of susceptible individuals are infected. Dengue, with a long serial interval and shorter season, may be constrained by its short transmission season rather than the depletion of susceptibles. Using mathematical modeling, we show that mass vaccination is most efficient, in terms of infections prevented per vaccine administered, at high levels of coverage for pathogens that have relatively long epidemic seasons, like influenza, and at low levels of coverage for pathogens with short epidemic seasons, like dengue. Therefore, the length of a pathogen’s epidemic season may need to be considered when evaluating the costs and benefits of vaccination programs.

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Modeling Cholera Outbreaks

Cited by 32 publications

References 68 publications

Modeling the Effect of Water, Sanitation, and Hygiene and Oral Cholera Vaccine Implementation in Haiti

Modeling the Effect of Water, Sanitation, and Hygiene and Oral Cholera Vaccine Implementation in Haiti

Achieving coordinated national immunity and cholera elimination in Haiti through vaccination

Seasonality and the effectiveness of mass vaccination

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