Mapping Yellow fever epidemics as a potential indicator of the historical range of Aedes aegypti in the United States.

BACKGROUND: Yellow fever (YF) plagued the United States from the 1690s until 1905, resulting in thousands of deaths. Within the US, Aedes aegypti is the only YF vector and almost no data exists for the location of this species prior to the early 1900s. OBJECTIVES: To determine the historical range of Ae. aegypti we examined the occurrence of YF epidemics across time and space. We hypothesized that historically Ae. aegypti was driven by human population density, like its contemporary range suggests. METHODS: To test this hypothesis, we compiled a list of YF cases in the US, human population density, location, and the number of people infected. This data was mapped using ArcGIS and was analyzed using linear regression models to determine the relationship among variables. FINDINGS: The historic range was generally south of 40º latitude, from Texas in the west to Florida in the east, with concentrations along major waterways like the Mississippi River. Infected individuals and human population density were strongly correlated across the whole dataset as well as by decade. MAIN CONCLUSIONS: Although other factors likely affected the range of Ae. aegypti, we found that human population density was related to the number of people infected with historic YF infections.

Robust network stability of mosquitoes and human pathogens of medical importance.

BACKGROUND: The exact number of mosquito species relevant to human health is unknown, posing challenges in understanding the scope and breadth of vector-pathogen relationships, and how resilient mosquito vector-pathogen networks are to targeted eradication of vectors. METHODS: We performed an extensive literature survey to determine the associations between mosquito species and their associated pathogens of human medical importance. For each vector-pathogen association, we then determined the strength of the associations (i.e., natural infection, lab infection, lab dissemination, lab transmission, known vector). A network analysis was used to identify relationships among all pathogens and vectors. Finally, we examined how elimination of either random or targeted species affected the extinction of pathogens. RESULTS: We found that 88 of 3578 mosquito species (2.5%) are known vectors for 78 human disease-causing pathogens; however, an additional 243 species (6.8%) were identified as potential or likely vectors, bringing the total of all mosquitos implicated in human disease to 331 (9.3%). Network analysis revealed that known vectors and pathogens were compartmentalized, with the removal of six vectors being enough to break the network (i.e., cause a pathogen to have no vector). However, the presence of potential or likely vectors greatly increased redundancies in the network, requiring more than 41 vectors to be eliminated before breaking the network. CONCLUSION: Although < 10% of mosquitoes are involved in transmitting pathogens that cause human disease, our findings point to inherent robustness in global mosquito vector-pathogen networks.