Ratnayake, RC; (2024) Case-Area Targeted Intervention for the Control of Cholera Epidemics in Crises: From Spatial Mathematical Modelling to Field Evaluation. PhD thesis, London School of Hygiene & Tropical Medicine. DOI: https://doi.org/10.17037/PUBS.04672999
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Abstract
Cholera transmission is rising globally in 2023, in the most deprived communities in Africa, Asia, the Middle East and in Haiti. Containment strategies for small outbreaks may be an efficient use of currently scarce vaccine doses and water and sanitation interventions usually delivered through mass campaigns. Case area-targeted intervention (CATI) aims to control small outbreaks with multiple interventions in ‘rings’ of 100–250m around case households. Currently, there is little evidence of CATI’simpact and delivery. In this thesis, I used evidence review, spatial analyses and mathematical modelling to investigate CATI’s potential impact in containing or reducing cholera transmission during outbreaks. Using a scoping review, I found moderate evidence that antibiotic chemoprophylaxis, single-dose vaccination, hygiene promotion, and water treatment can rapidly limittransmission in the household and surrounding 100m radius for 7 days following case presentation. To investigate whether CATI can be implemented within 7 days in fragile settings where cholera emerges, I conducted a statistical review of milestones in 76 cholera outbreaks in 34 countries. Median delay to outbreak detection and response were 5 and 10 days, respectively, revealing an opportunity for CATI. Localized eventbased surveillance, rapid diagnostic testing, and integration of alert and response functions among local teams were qualitatively linked to early detection and response. Next, I analysed the spatiotemporal clustering of cholera in Uvira, Democratic Republic of Congo, where it is endemic. This suggested a 1000m zone of infection risk around a case within 5 days of presentation, and the timing and locations of 26 recurring clusters.To quantify CATI’s potential control in the first 60 days of an outbreak, I developed a spatially explicit dynamic model driven by a spatial force of infection around new cases. This showed that prompt implementation of CATI with vaccination, antibiotics, and water treatment in a 150m radius around new cases is potentially effective in containingcholera within the first 60 days of an outbreak and requires <6% of the population that would have been addressed in a mass campaign. Overall, this thesis demonstrates the potential speed and impact of CATI, when vaccination is included, on containing cholera outbreaks in their earliest phase. While CATI is inherently reactive and cannot achieve long-lasting protection for a larger population, it may be able to contain outbreaks with fewer resources in order to reduce cases and strain on case management. In an era of vaccine scarcity, this thesis provides rationale to procure small vaccine stocks (and other interventions) for district-levelactivation of CATI. This work has also informed the development of a now-concluded observational study to measure CATI’s impact.
Item Type | Thesis |
---|---|
Thesis Type | Doctoral |
Thesis Name | PhD |
Contributors | Checchi, F and Edmunds, J |
Faculty and Department |
Faculty of Epidemiology and Population Health Faculty of Epidemiology and Population Health > Dept of Infectious Disease Epidemiology & Dynamics (2023-) |
Funder Name | Canadian Institutes of Health Research |
Grant number | DFS-16426 |
Copyright Holders | Ruwan Chaminda Ratnayake |
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Filename: 2024_EPH_PhD_Ratnayake_R.pdf
Licence: Creative Commons: Attribution-Noncommercial-No Derivative Works 4.0
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