Journal Article > CommentaryFull Text
Am J Trop Med Hyg. 1 June 2017; Volume 96 (Issue 6); 1270-1273.; DOI:10.4269/ajtmh.16-0427
Lessler J, Azman AS, McKay H, Moore SM
Am J Trop Med Hyg. 1 June 2017; Volume 96 (Issue 6); 1270-1273.; DOI:10.4269/ajtmh.16-0427
The importance of spatial clusters, or "hotspots," in infectious disease epidemiology has been increasingly recognized, and targeting hotspots is often seen as an important component of disease-control strategies. However, the precise meaning of "hotspot" varies widely in current research and policy documents. Hotspots have been variously described as areas of elevated incidence or prevalence, higher transmission efficiency or risk, or higher probability of disease emergence. This ambiguity has led to confusion and may result in mistaken inferences regarding the best way to target interventions. We surveyed the literature on epidemiologic hotspots, examining the multitude of ways in which the term is used; and highlight the difference in the geographic scale of hotspots and the properties they are supposed to have. In response to the diversity in the term's usage, we advocate the use of more precise terms, such as "burden hotspot," "transmission hotspot," and "emergence hotspot," as well as explicit specification of the spatiotemporal scale of interest. Increased precision in terminology is needed to ensure clear and effective policies for disease control.
Journal Article > CommentaryFull Text
Bull World Health Organ. 1 June 2018; Volume 96 (Issue 6); 428-435.; DOI:10.2471/BLT.17.207175
Mbangombe M, Pezzoli L, Reeder B, Kabuluzi S, Msyamboza K, et al.
Bull World Health Organ. 1 June 2018; Volume 96 (Issue 6); 428-435.; DOI:10.2471/BLT.17.207175
PROBLEM
With limited global supplies of oral cholera vaccine, countries need to identify priority areas for vaccination while longer-term solutions, such as water and sanitation infrastructure, are being developed.
APPROACH
In 2017, Malawi integrated oral cholera vaccine into its national cholera control plan. The process started with a desk review and analysis of previous surveillance and risk factor data. At a consultative meeting, researchers, national health and water officials and representatives from nongovernmental and international organizations reviewed the data and local epidemiological knowledge to determine priority districts for oral cholera vaccination. The final stage was preparation of an application to the global oral cholera vaccine stockpile for non-emergency use.
LOCAL SETTING
Malawi collects annual data on cholera and most districts have reported cases at least once since the 1970s.
RELEVANT CHANGES
The government’s application for 3.2 million doses of vaccine to be provided over 20 months in 12 districts was accepted in April 2017. By April 2018, over 1 million doses had been administered in five districts. Continuing surveillance in districts showed that cholera outbreaks were notably absent in vaccinated high-risk areas, despite a national outbreak in 2017–2018.
LESSONS LEARNT
Augmenting advanced mapping techniques with local information helped us extend priority areas beyond those identified as high-risk based on cholera incidence reported at the district level. Involvement of the water, sanitation and hygiene sectors is key to ensuring that short-term gains from cholera vaccine are backed by longer-term progress in reducing cholera transmission.
With limited global supplies of oral cholera vaccine, countries need to identify priority areas for vaccination while longer-term solutions, such as water and sanitation infrastructure, are being developed.
APPROACH
In 2017, Malawi integrated oral cholera vaccine into its national cholera control plan. The process started with a desk review and analysis of previous surveillance and risk factor data. At a consultative meeting, researchers, national health and water officials and representatives from nongovernmental and international organizations reviewed the data and local epidemiological knowledge to determine priority districts for oral cholera vaccination. The final stage was preparation of an application to the global oral cholera vaccine stockpile for non-emergency use.
LOCAL SETTING
Malawi collects annual data on cholera and most districts have reported cases at least once since the 1970s.
RELEVANT CHANGES
The government’s application for 3.2 million doses of vaccine to be provided over 20 months in 12 districts was accepted in April 2017. By April 2018, over 1 million doses had been administered in five districts. Continuing surveillance in districts showed that cholera outbreaks were notably absent in vaccinated high-risk areas, despite a national outbreak in 2017–2018.
LESSONS LEARNT
Augmenting advanced mapping techniques with local information helped us extend priority areas beyond those identified as high-risk based on cholera incidence reported at the district level. Involvement of the water, sanitation and hygiene sectors is key to ensuring that short-term gains from cholera vaccine are backed by longer-term progress in reducing cholera transmission.
Journal Article > ResearchFull Text
Lancet. 1 May 2018; Volume 391 (Issue 10133); DOI:10.1016/S0140-6736(17)33050-7
Lessler J, Moore SM, Luquero FJ, McKay H, Grais RF, et al.
Lancet. 1 May 2018; Volume 391 (Issue 10133); DOI:10.1016/S0140-6736(17)33050-7
Cholera remains a persistent health problem in sub-Saharan Africa and worldwide. Cholera can be controlled through appropriate water and sanitation, or by oral cholera vaccination, which provides transient (∼3 years) protection, although vaccine supplies remain scarce. We aimed to map cholera burden in sub-Saharan Africa and assess how geographical targeting could lead to more efficient interventions.
Journal Article > ResearchFull Text
Proc Natl Acad Sci U S A. 10 April 2017; Volume 114 (Issue 17); 4436-4441.; DOI:10.1073/pnas.1617218114
Moore SM, Azman AS, Zaitchik BF, Mintz ED, Brunkard J, et al.
Proc Natl Acad Sci U S A. 10 April 2017; Volume 114 (Issue 17); 4436-4441.; DOI:10.1073/pnas.1617218114
The El Niño Southern Oscillation (ENSO) and other climate patterns can have profound impacts on the occurrence of infectious diseases ranging from dengue to cholera. In Africa, El Niño conditions are associated with increased rainfall in East Africa and decreased rainfall in southern Africa, West Africa, and parts of the Sahel. Because of the key role of water supplies in cholera transmission, a relationship between El Niño events and cholera incidence is highly plausible, and previous research has shown a link between ENSO patterns and cholera in Bangladesh. However, there is little systematic evidence for this link in Africa. Using high-resolution mapping techniques, we find that the annual geographic distribution of cholera in Africa from 2000 to 2014 changes dramatically, with the burden shifting to continental East Africa-and away from Madagascar and portions of southern, Central, and West Africa-where almost 50,000 additional cases occur during El Niño years. Cholera incidence during El Niño years was higher in regions of East Africa with increased rainfall, but incidence was also higher in some areas with decreased rainfall, suggesting a complex relationship between rainfall and cholera incidence. Here, we show clear evidence for a shift in the distribution of cholera incidence throughout Africa in El Niño years, likely mediated by El Niño's impact on local climatic factors. Knowledge of this relationship between cholera and climate patterns coupled with ENSO forecasting could be used to notify countries in Africa when they are likely to see a major shift in their cholera risk.
Journal Article > ResearchAbstract Only
Science. 10 November 2017; Volume 358 (Issue 6364); 785-789.; DOI:10.1126/science.aad5901
Weill FX, Domman D, Njamkepo E, Tarr C, Rauzier J, et al.
Science. 10 November 2017; Volume 358 (Issue 6364); 785-789.; DOI:10.1126/science.aad5901
The seventh cholera pandemic has heavily affected Africa, although the origin and continental spread of the disease remain undefined. We used genomic data from 1070 Vibrio cholerae O1 isolates, across 45 African countries and over a 49-year period, to show that past epidemics were attributable to a single expanded lineage. This lineage was introduced at least 11 times since 1970, into two main regions, West Africa and East/Southern Africa, causing epidemics that lasted up to 28 years. The last five introductions into Africa, all from Asia, involved multidrug-resistant sublineages that replaced antibiotic-susceptible sublineages after 2000. This phylogenetic framework describes the periodicity of lineage introduction and the stable routes of cholera spread, which should inform the rational design of control measures for cholera in Africa.
Journal Article > LetterFull Text
Lancet. 19 February 2015; Volume 385 (Issue 9971); DOI:10.1016/S0140-6736(15)60178-7
Azman AS, Legros D, Lessler J, Luquero FJ, Moore SM
Lancet. 19 February 2015; Volume 385 (Issue 9971); DOI:10.1016/S0140-6736(15)60178-7