Collaborative Research: Modeling the Spatial and Temporal Dynamics of Vector-borne Diseases in Florida: The Case of Zika Outbreak in 2016

Overview: Global change in the 21st century poses a significant threat to human health and vector-borne diseases (VBD) are likely to change in distribution and intensity as a result of climate shifts associated with global warming. Prediction and control of future vector-borne disease outbreaks, vector spread, and human behavior remain extremely challenging. Humans travel more frequently on scales from local to global. Such movements can spread disease pathogens and their vectors over long distances and can threaten public health. Thus, it is essential to consider current and future influences of global change and host movement on the transmission dynamics and spatial and temporal patterns of vector-borne diseases. Dengue, chikungunya, and Zika, primarily transmitted by the same Aedes mosquito species (Aedes aegypti and Ae. albopictus), have been imported into the U.S. and have caused local outbreaks in Florida (dengue in 2009-2010 and 2013, chikungunya in 2014, Zika in 2016). Recent studies on mosquitoes indicate that vector senescence is important as part of the modeling procedure and that not modeling realistic death rates may lead to inaccuracies when estimating the transmission and prevalence of VBD. The age-distribution of hosts is also very important since Zika virus can be passed from a pregnant woman to her fetus which can cause microcephaly and other severe fetal brain defects. This proposal is aimed to model and describe the spatial and temporal dynamics of VBD in Florida. Structured (spacediscrete and age) population models will be used to determine the birth, growth, death, and dispersal rates of mosquitoes and humans and their interactions with the environment and with each other. The goal is then to investigate how the structuring variables and environmental factors affect the properties of these systems and how to prevent and control the spatial spread of VBD. Intellectual Merit: (i) Based on the local outbreak of Zika in three regions, Wynwood, Miami Beach, and Little River, in Florida in 2016, the PIs propose a multi-scale multi-patch model to study how VBD are spread first geographically by long-distance movement of humans and then locally by short-distance movement of both mosquitoes and humans. Mathematical, statistical and computational analyses of the model will be carried out to better understand the factors that contributed to the geographical spread of Zika among these regions during the 2016 outbreak and to be better prepared to anticipate and respond to reemerging arboviruses such as dengue virus, chikungunya virus and yellow fever virus, as well as similar arboviruses yet to emerge. (ii) Construct age-structured models to study the effect of age distributions of both mosquitoes and humans on the transmission dynamics of VBD and use the model to design optimal vector control policies and to access disease risk for different age groups. (iii) Study the nonlinear dynamics of semilinear periodic equations in Banach spaces and apply the results to age-structured vector-borne disease models with seasonal change. Part (iii) will be transformative since the results can be used to study various periodic biological models described by age-structured equations, delay differential equations and reaction-diffusion equations. Broader Impacts: The proposed study will be helpful in designing and introducing public health policies on the control and prevention of the spread of vector-borne diseases, such as dengue, chikungunya and Zika, in Florida. The proposed project is also closely related to the courses Mathematical Biology and Mathematical Epidemiology the PI has developed at the University of Miami for senior undergraduate students and graduate students from biology, biomedical engineering, epidemiology, mathematics, and ocean science. The proposed project will help the PIs to continue focusing on interdisciplinary training of undergraduates, graduates, and postdoctoral fellows with diverse backgrounds. The PI has been (co)- organizing a number of international conferences and workshops and has lectured at several summer schools on mathematical biology. One of the goals of these activities is to help communication and collaboration between researchers, in particular young researchers from under-represented groups and from different disciplines, involved in mathematical biology