Journal Article > ResearchFull Text
Epidemiol Infect. 2013 October 11; Volume 142 (Issue 8); DOI:10.1017/S0950268813002562
Grandesso F, Allan M, Jean-Simon PSJ, Boncy J, Blake A, et al.
Epidemiol Infect. 2013 October 11; Volume 142 (Issue 8); DOI:10.1017/S0950268813002562
SUMMARY Two community-based density case-control studies were performed to assess risk factors for cholera transmission during inter-peak periods of the ongoing epidemic in two Haitian urban settings, Gonaives and Carrefour. The strongest associations were: close contact with cholera patients (sharing latrines, visiting cholera patients, helping someone with diarrhoea), eating food from street vendors and washing dishes with untreated water. Protective factors were: drinking chlorinated water, receiving prevention messages via television, church or training sessions, and high household socioeconomic level. These findings suggest that, in addition to contaminated water, factors related to direct and indirect inter-human contact play an important role in cholera transmission during inter-peak periods. In order to reduce cholera transmission in Haiti intensive preventive measures such as hygiene promotion and awareness campaigns should be implemented during inter-peak lulls, when prevention activities are typically scaled back.
Journal Article > ResearchFull Text
PLoS Negl Trop Dis. 2013 August 15; Volume 7 (Issue 8); DOI:10.1371/journal.pntd.0002366
Martinez-Pino I, Luquero FJ, Sakoba K, Sylla S, Haile M, et al.
PLoS Negl Trop Dis. 2013 August 15; Volume 7 (Issue 8); DOI:10.1371/journal.pntd.0002366
During the 2012 cholera outbreak in the Republic of Guinea, the Ministry of Health, supported by Médecins Sans Frontières - Operational Center Geneva, used the oral cholera vaccine Shanchol as a part of the emergency response. The rapid diagnostic test (RDT) Crystal VC, widely used during outbreaks, detects lipopolysaccharide antigens of Vibrio cholerae O1 and O139, both included in Shanchol. In the context of reactive use of a whole-cell cholera vaccine in a region where cholera cases have been reported, it is essential to know what proportion of vaccinated individuals would be reactive to the RDT and for how long after vaccination.
Journal Article > ResearchFull Text
Lancet Planet Health. 2020 December 1; Volume 4; DOI:10.1016/S2542-5196(20)30255-2
Jones FK, Wamala JF, Rumunu J, Mawien PN, Kol MT, et al.
Lancet Planet Health. 2020 December 1; Volume 4; DOI:10.1016/S2542-5196(20)30255-2
Background
Between 2014 and 2017, successive cholera epidemics occurred in South Sudan within the context of civil war, population displacement, flooding, and drought. We aim to describe the spatiotemporal and molecular features of the three distinct epidemic waves and explore the role of vaccination campaigns, precipitation, and population movement in shaping cholera spread in this complex setting.
Methods
In this descriptive epidemiological study, we analysed cholera linelist data to describe the spatiotemporal progression of the epidemics. We placed whole-genome sequence data from pandemic Vibrio cholerae collected throughout these epidemics into the global phylogenetic context. Using whole-genome sequence data in combination with other molecular attributes, we characterise the relatedness of strains circulating in each wave and the region. We investigated the association of rainfall and the instantaneous basic reproduction number using distributed lag non-linear models, compared county-level attack rates between those with early and late reactive vaccination campaigns, and explored the consistency of the spatial patterns of displacement and suspected cholera case reports.
Findings
The 2014 (6389 cases) and 2015 (1818 cases) cholera epidemics in South Sudan remained spatially limited whereas the 2016–17 epidemic (20 438 cases) spread among settlements along the Nile river. Initial cases of each epidemic were reported in or around Juba soon after the start of the rainy season, but we found no evidence that rainfall modulated transmission during each epidemic. All isolates analysed had similar genotypic and phenotypic characteristics, closely related to sequences from Uganda and Democratic Republic of the Congo. Large-scale population movements between counties of South Sudan with cholera outbreaks were consistent with the spatial distribution of cases. 21 of 26 vaccination campaigns occurred during or after the county-level epidemic peak. Counties vaccinated on or after the peak incidence week had 2·2 times (95% CI 2·1–2·3) higher attack rates than those where vaccination occurred before the peak.
Interpretation
Pandemic V cholerae of the same clonal origin was isolated throughout the study period despite interepidemic periods of no reported cases. Although the complex emergency in South Sudan probably shaped some of the observed spatial and temporal patterns of cases, the full scope of transmission determinants remains unclear. Timely and well targeted use of vaccines can reduce the burden of cholera; however, rapid vaccine deployment in complex emergencies remains challenging.
Between 2014 and 2017, successive cholera epidemics occurred in South Sudan within the context of civil war, population displacement, flooding, and drought. We aim to describe the spatiotemporal and molecular features of the three distinct epidemic waves and explore the role of vaccination campaigns, precipitation, and population movement in shaping cholera spread in this complex setting.
Methods
In this descriptive epidemiological study, we analysed cholera linelist data to describe the spatiotemporal progression of the epidemics. We placed whole-genome sequence data from pandemic Vibrio cholerae collected throughout these epidemics into the global phylogenetic context. Using whole-genome sequence data in combination with other molecular attributes, we characterise the relatedness of strains circulating in each wave and the region. We investigated the association of rainfall and the instantaneous basic reproduction number using distributed lag non-linear models, compared county-level attack rates between those with early and late reactive vaccination campaigns, and explored the consistency of the spatial patterns of displacement and suspected cholera case reports.
Findings
The 2014 (6389 cases) and 2015 (1818 cases) cholera epidemics in South Sudan remained spatially limited whereas the 2016–17 epidemic (20 438 cases) spread among settlements along the Nile river. Initial cases of each epidemic were reported in or around Juba soon after the start of the rainy season, but we found no evidence that rainfall modulated transmission during each epidemic. All isolates analysed had similar genotypic and phenotypic characteristics, closely related to sequences from Uganda and Democratic Republic of the Congo. Large-scale population movements between counties of South Sudan with cholera outbreaks were consistent with the spatial distribution of cases. 21 of 26 vaccination campaigns occurred during or after the county-level epidemic peak. Counties vaccinated on or after the peak incidence week had 2·2 times (95% CI 2·1–2·3) higher attack rates than those where vaccination occurred before the peak.
Interpretation
Pandemic V cholerae of the same clonal origin was isolated throughout the study period despite interepidemic periods of no reported cases. Although the complex emergency in South Sudan probably shaped some of the observed spatial and temporal patterns of cases, the full scope of transmission determinants remains unclear. Timely and well targeted use of vaccines can reduce the burden of cholera; however, rapid vaccine deployment in complex emergencies remains challenging.
Journal Article > ResearchFull Text
Public Health Action. 2020 September 21; Volume 10; DOI:10.5588/pha.19.0074
Makelele JPK, Ade S, Takarinda KC, Manzi M, Gil Cuesta J, et al.
Public Health Action. 2020 September 21; Volume 10; DOI:10.5588/pha.19.0074
Setting: In 1995, a rapid response project for humanitarian and medical emergencies, including outbreak responses, named ‘Pool d’Urgence Congo’ (PUC), was implemented in the Democratic Republic of Congo by Médecins Sans Frontières.
Objective: To assess the outcomes of cholera and measles outbreak alerts that were received in the PUC surveillance system between 2016 and 2018.
Design: This was a retrospective cross-sectional study.
Results: Overall, 459 outbreak alerts were detected, respectively 69% and 31% for cholera and measles. Of these, 32% were actively detected and 68% passively detected. Most alerts (90%) required no intervention and 10% of alerts had an intervention. There were 25% investigations that were not carried out despite thresholds being met; 17% interventions were not performed, the main reported reason being PUC operational capacity was exceeded. Confirmed cholera and measles outbreaks that met an investigation threshold comprised respectively 90% and 76% of alerts; 59% of measles investigations were followed by a delayed outbreak response of 14 days (n = 10 outbreaks).
Conclusion: Some alerts for cholera and measles outbreaks that were detected in the PUC system did not lead to a response even when required; the main reported reason was limited operational capacity to respond to all of them.
Objective: To assess the outcomes of cholera and measles outbreak alerts that were received in the PUC surveillance system between 2016 and 2018.
Design: This was a retrospective cross-sectional study.
Results: Overall, 459 outbreak alerts were detected, respectively 69% and 31% for cholera and measles. Of these, 32% were actively detected and 68% passively detected. Most alerts (90%) required no intervention and 10% of alerts had an intervention. There were 25% investigations that were not carried out despite thresholds being met; 17% interventions were not performed, the main reported reason being PUC operational capacity was exceeded. Confirmed cholera and measles outbreaks that met an investigation threshold comprised respectively 90% and 76% of alerts; 59% of measles investigations were followed by a delayed outbreak response of 14 days (n = 10 outbreaks).
Conclusion: Some alerts for cholera and measles outbreaks that were detected in the PUC system did not lead to a response even when required; the main reported reason was limited operational capacity to respond to all of them.
Journal Article > ResearchFull Text
Vaccine. 2006 May 29; Volume 24 (Issue 22); 4890-4895.; DOI:10.1016/j.vaccine.2005.10.006
Cavailler P, Perroud V, Mcchesney M, Ampuero S, Guerin PJ, et al.
Vaccine. 2006 May 29; Volume 24 (Issue 22); 4890-4895.; DOI:10.1016/j.vaccine.2005.10.006
We conducted a study to assess the feasibility and the potential vaccine coverage of a mass vaccination campaign using a two-dose oral cholera vaccine in an urban endemic neighbourhood of Beira, Mozambique. The campaign was conducted from December 2003 to January 2004. Overall 98,152 doses were administered, and vaccine coverage of the target population was 58.6% and 53.6% for the first and second rounds, respectively. The direct cost of the campaign, which excludes the price of the vaccine, amounted to slightly over 90,000 dollars, resulting in the cost per fully vaccinated person of 2.09 dollars, which is relatively high. However, in endemic settings where outbreaks are likely to occur, integrating cholera vaccination into the routine activities of the public health system could reduce such costs.
Protocol > Research Study
Fernandez MAL, Schomaker M, Mason PR, Fesselet JF, Baudot Y, et al.
2012 June 18
BACKGROUND
In highly populated African urban areas where access to clean water is a challenge, water source contamination is one of the most cited risk factors in a cholera epidemic. During the rainy season, where there is either no sewage disposal or working sewer system, runoff of rains follows the slopes and gets into the lower parts of towns where shallow wells could easily become contaminated by excretes. In cholera endemic areas, spatial information about topographical elevation could help to guide preventive interventions. This study aims to analyze the association between topographic elevation and the distribution of cholera cases in Harare during the cholera epidemic in 2008 and 2009.
METHODS
We developed an ecological study using secondary data. First, we described attack rates by suburb and then calculated rate ratios using whole Harare as reference. We illustrated the average elevation and cholera cases by suburbs using geographical information. Finally, we estimated a generalized linear mixed model (under the assumption of a Poisson distribution) with an Empirical Bayesian approach to model the relation between the risk of cholera and the elevation in meters in Harare. We used a random intercept to allow for spatial correlation of neighboring suburbs.
RESULTS
This study identifies a spatial pattern of the distribution of cholera cases in the Harare epidemic, characterized by a lower cholera risk in the highest elevation suburbs of Harare. The generalized linear mixed model showed that for each 100 meters of increase in the topographical elevation, the cholera risk was 30% lower with a rate ratio of 0.70 (95% confidence interval=0.66-0.76). Sensitivity analysis confirmed the risk reduction with an overall estimate of the rate ratio between 20% and 40%.
CONCLUSION
This study highlights the importance of considering topographical elevation as a geographical and environmental risk factor in order to plan cholera preventive activities linked with water and sanitation in endemic areas. Furthermore, elevation information, among other risk factors, could help to spatially orientate cholera control interventions during an epidemic.
In highly populated African urban areas where access to clean water is a challenge, water source contamination is one of the most cited risk factors in a cholera epidemic. During the rainy season, where there is either no sewage disposal or working sewer system, runoff of rains follows the slopes and gets into the lower parts of towns where shallow wells could easily become contaminated by excretes. In cholera endemic areas, spatial information about topographical elevation could help to guide preventive interventions. This study aims to analyze the association between topographic elevation and the distribution of cholera cases in Harare during the cholera epidemic in 2008 and 2009.
METHODS
We developed an ecological study using secondary data. First, we described attack rates by suburb and then calculated rate ratios using whole Harare as reference. We illustrated the average elevation and cholera cases by suburbs using geographical information. Finally, we estimated a generalized linear mixed model (under the assumption of a Poisson distribution) with an Empirical Bayesian approach to model the relation between the risk of cholera and the elevation in meters in Harare. We used a random intercept to allow for spatial correlation of neighboring suburbs.
RESULTS
This study identifies a spatial pattern of the distribution of cholera cases in the Harare epidemic, characterized by a lower cholera risk in the highest elevation suburbs of Harare. The generalized linear mixed model showed that for each 100 meters of increase in the topographical elevation, the cholera risk was 30% lower with a rate ratio of 0.70 (95% confidence interval=0.66-0.76). Sensitivity analysis confirmed the risk reduction with an overall estimate of the rate ratio between 20% and 40%.
CONCLUSION
This study highlights the importance of considering topographical elevation as a geographical and environmental risk factor in order to plan cholera preventive activities linked with water and sanitation in endemic areas. Furthermore, elevation information, among other risk factors, could help to spatially orientate cholera control interventions during an epidemic.
Journal Article > ResearchFull Text
Int J Infect Dis. 2022 September 1; Volume 122; 215-221.; DOI:10.1016/j.ijid.2022.05.039
Zheng Q, Luquero FJ, Ciglenecki I, Wamala JF, Abubakar A, et al.
Int J Infect Dis. 2022 September 1; Volume 122; 215-221.; DOI:10.1016/j.ijid.2022.05.039
BACKGROUND
Cholera remains a public health threat but is inequitably distributed across sub-Saharan Africa. Lack of standardized reporting and inconsistent outbreak definitions limit our understanding of cholera outbreak epidemiology.
METHODS
From a database of cholera incidence and mortality, we extracted data from sub-Saharan Africa and reconstructed outbreaks of suspected cholera starting in January 2010 to December 2019 based on location-specific average weekly incidence rate thresholds. We then described the distribution of key outbreak metrics.
RESULTS
We identified 999 suspected cholera outbreaks in 744 regions across 25 sub-Saharan African countries. The outbreak periods accounted for 1.8 billion person-months (2% of the total during this period) from January 2010 to January 2020. Among 692 outbreaks reported from second-level administrative units (e.g., districts), the median attack rate was 0.8 per 1000 people (interquartile range (IQR), 0.3-2.4 per 1000), the median epidemic duration was 13 weeks (IQR, 8-19), and the median early outbreak reproductive number was 1.8 (range, 1.1-3.5). Larger attack rates were associated with longer times to outbreak peak, longer epidemic durations, and lower case fatality risks.
CONCLUSIONS
This study provides a baseline from which the progress toward cholera control and essential statistics to inform outbreak management in sub-Saharan Africa can be monitored.
Cholera remains a public health threat but is inequitably distributed across sub-Saharan Africa. Lack of standardized reporting and inconsistent outbreak definitions limit our understanding of cholera outbreak epidemiology.
METHODS
From a database of cholera incidence and mortality, we extracted data from sub-Saharan Africa and reconstructed outbreaks of suspected cholera starting in January 2010 to December 2019 based on location-specific average weekly incidence rate thresholds. We then described the distribution of key outbreak metrics.
RESULTS
We identified 999 suspected cholera outbreaks in 744 regions across 25 sub-Saharan African countries. The outbreak periods accounted for 1.8 billion person-months (2% of the total during this period) from January 2010 to January 2020. Among 692 outbreaks reported from second-level administrative units (e.g., districts), the median attack rate was 0.8 per 1000 people (interquartile range (IQR), 0.3-2.4 per 1000), the median epidemic duration was 13 weeks (IQR, 8-19), and the median early outbreak reproductive number was 1.8 (range, 1.1-3.5). Larger attack rates were associated with longer times to outbreak peak, longer epidemic durations, and lower case fatality risks.
CONCLUSIONS
This study provides a baseline from which the progress toward cholera control and essential statistics to inform outbreak management in sub-Saharan Africa can be monitored.
Journal Article > ResearchAbstract
Trans R Soc Trop Med Hyg. 2010 November 13; Volume 105 (Issue 1); DOI:10.1016/j.trstmh.2010.10.001
Luque Fernandez MA, Mason PR, Gray H, Bauernfeind A, Maes P
Trans R Soc Trop Med Hyg. 2010 November 13; Volume 105 (Issue 1); DOI:10.1016/j.trstmh.2010.10.001
This ecological study describes the cholera epidemic in Harare during 2008-2009 and identifies patterns that may explain transmission. Rates ratios of cholera cases by suburb were calculated by a univariate regression Poisson model and then, through an Empirical Bayes modelling, smoothed rate ratios were estimated and represented geographically. Mbare and southwest suburbs of Harare presented higher rate ratios. Suburbs attack rates ranged from 1.2 (95% Cl = 0.7-1.6) cases per 1000 people in Tynwald to 90.3 (95% Cl = 82.8-98.2) in Hopley. The identification of this spatial pattern in the spread, characterised by low risk in low density residential housing, and a higher risk in high density south west suburbs and Mbare, could be used to advocate for improving water and sanitation conditions and specific preparedness measures in the most affected areas.
Journal Article > ResearchFull Text
Epidemiol Infect. 2020 March 13; Volume 148; DOI:10.1017/S095026882000062X
Ferreras E, Blake A, Chewe O, Mwaba J, Zulu G, et al.
Epidemiol Infect. 2020 March 13; Volume 148; DOI:10.1017/S095026882000062X
We conducted a matched case-control (MCC), test-negative case-control (TNCC) and case-cohort study in 2016 in Lusaka, Zambia, following a mass vaccination campaign. Confirmed cholera cases served as cases in all three study designs. In the TNCC, control-subjects were cases with negative cholera culture and polymerase chain reaction results. Matched controls by age and sex were selected among neighbours of the confirmed cases in the MCC study. For the case-cohort study, we recruited a cohort of randomly selected individuals living in areas considered at-risk of cholera. We recruited 211 suspected cases (66 confirmed cholera cases and 145 non-cholera diarrhoea cases), 1055 matched controls and a cohort of 921. Adjusted vaccine effectiveness of one dose of oral cholera vaccine (OCV) was 88.9% (95% confidence interval (CI) 42.7–97.8) in the MCC study, 80.2% (95% CI: 16.9–95.3) in the TNCC design and 89.4% (95% CI: 64.6–96.9) in the case-cohort study. Three study designs confirmed the short-term effectiveness of single dose OCV. Major healthcare-seeking behaviour bias did not appear to affect our estimates. Most of the protection among vaccinated individuals could be attributed to the direct effect of the vaccine.
Journal Article > ResearchFull Text
Sci Rep. 2016 October 24; Volume 6; 35742.; DOI:10.1038/srep35742
Iyer AS, Ryan ET, Martin S, Legros D, Lessler J, et al.
Sci Rep. 2016 October 24; Volume 6; 35742.; DOI:10.1038/srep35742
Despite recent large-scale cholera outbreaks, little is known about the immunogenicity of oral cholera vaccines (OCV) in African populations, particularly among those at highest cholera risk. During a 2015 preemptive OCV campaign among internally displaced persons in South Sudan, a year after a large cholera outbreak, we enrolled 37 young children (1-5 years old), 67 older children (6-17 years old) and 101 adults (≥18 years old), who received two doses of OCV (Shanchol) spaced approximately 3 weeks apart. Cholera-specific antibody responses were determined at days 0, 21 and 35 post-immunization. High baseline vibriocidal titers (>80) were observed in 21% of the participants, suggesting recent cholera exposure or vaccination. Among those with titers ≤80, 90% young children, 73% older children and 72% adults seroconverted (≥4 fold titer rise) after the 1(st) OCV dose; with no additional seroconversion after the 2(nd) dose. Post-vaccination immunological endpoints did not differ across age groups. Our results indicate Shanchol was immunogenic in this vulnerable population and that a single dose alone may be sufficient to achieve similar short-term immunological responses to the currently licensed two-dose regimen. While we found no evidence of differential response by age, further immunologic and epidemiologic studies are needed.