Abstract
BackgroundWhile the global burden of typhoid fever has been often brought up for attention, the detailed surveillance information has only been available for the limited number of countries. As more efficacious vaccines will be available in the near future, it is essential to understand the geographically diverse patterns of typhoid risk levels and to prioritize the right populations for vaccination to effectively control the disease.MethodsA composite index called the typhoid risk factor (TRF) index was created based on data with the Global Positioning System (GPS). Demographic and Health Surveys (DHS) and National Geographical Data Center (NGDC) satellite lights data were used for this analysis. A count model was adopted to validate the TRF index against the existing surveillance burden data. The TRF index was then re-estimated for 66 countries using the most recent data and mapped out for two geographical levels (sub-national boundary and grid-cell levels).ResultsThe TRF index which consists of drinking water sources, toilet facility types, and population density appeared to be statistically significant to explain variation in the disease burden data. The mapping analysis showed that typhoid risk levels vary not only by country but also by sub-national region. The grid-cell level analysis highlighted that the distribution of typhoid risk factors is uneven within the sub-national boundary level. Typhoid risk levels are geographically heterogeneous.ConclusionsGiven the insufficient number of surveillance studies, the TRF index serves as a useful tool by capturing multiple risk factors of the disease into a single indicator. This will help decision makers identify high risk areas for typhoid as well as other waterborne diseases. Further, the study outcome can guide researchers to find relevant places for future surveillance studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-2074-1) contains supplementary material, which is available to authorized users.
Highlights
While the global burden of typhoid fever has been often brought up for attention, the detailed surveillance information has only been available for the limited number of countries
This study proposes a new way of recognizing the global dynamics of exposure to typhoid infection by creating a composite index called the typhoid risk factor (TRF) index based on the fundamental risk factors of the disease
The TRF index constructed in this study summarized multiple risk factors of the disease as a single indicator which enables people to interpret
Summary
While the global burden of typhoid fever has been often brought up for attention, the detailed surveillance information has only been available for the limited number of countries. As more efficacious vaccines will be available in the near future, it is essential to understand the geographically diverse patterns of typhoid risk levels and to prioritize the right populations for vaccination to effectively control the disease. Typhoid fever remains a major public health concern in less developed countries [1,2,3]. Typhoid is more common in impoverished areas with unsafe drinking water sources and poor sanitation. This can be exacerbated in areas where rapid population expansion is observed. More efficacious vaccines such as typhoid conjugate vaccines, are expected to be approved by World Health Organization (WHO) prequalification program in coming years. Considering many developing countries face limited resources and must contend with controlling typhoid transmission in
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