Research

My area of interest is applied mathematics, specifically mathematical modeling. I am currently involved in projects concerned with vectored-plant diseases and modeling patient flow through hospital emergency departments. A brief description of each project is presented below.

Citrus Greening

Citrus greening disease, also called huanglongbing (HLB), is a vector-transmitted bacterial disease of citrus trees that is widespread in the world. HLB is difficult to manage and continued production of citrus has proven difficult and expensive in areas where it is widespread. HLB is spread by two species of citrus psyllids. One of the species, Diaphorina citri (D. citri), has been present in Florida since 1998. The strain of bacteria, Candidatus Liberibacter asiaticus (CLas) was first detected in South Florida in 2005. We develop a model that describes the spread of the Las among trees in a grove by including pathways of transmission among psyllids.

One of the main symptoms of the disease, green fruit (picture from USDA)
One of the main symptoms of the disease, green fruit
(picture from USDA)
Diaphorina citri, commonly known as Asian citrus psyllid (picture from Michael E. Rogers)
Diaphorina citri, commonly known as Asian citrus psyllid
(picture from Michael E. Rogers)

 

Poster

  • Lee J, Halbert SE, Keesling JE, Singer BH. A model for the spread of HLB attributed to Diaphorina citri. Third Annual Citrus Health Research Forum, Fort Collins, CO.
    Poster (pdf)
    Supplemental Information

Muscavirus (MdSGHV)

This project investigates the population dynamics of Musca domestica, more commonly known as house flies. We use a system of differential equations to model the different modes of transmission among the flies and proposed a new pathway for transmission of the virus among the house flies. The purpose is to determine whether MdSGHV would succeed as a biological control agent for the population of house flies.

High fly densities and aggressive behaviors are assumed to promote viral transmission among adult flies.
High fly densities and aggressive behaviors are assumed to promote viral transmission among adult flies.
Musca domestica (house fly) picture from Wikipedia
Musca domestica (house fly)
picture from Wikipedia

Papers:

  • Lietze VU, Keesling JE, Lee J, Vallejo CR, Geden CJ, and Boucias DG (2013) Muscavirus (MdSGHV) disease dynamics in house fly populations – How is this virus transmitted and has it potential as a biological control agent? J. Invertebrate Pathol 112:S40-S43.
  • Vallejo CR, Lee J, Keesling JE, Geden CJ, Lietz VU, Boucias DG (2013) A mathematical model that describes modes of MdSGHV transmission within house fly populations. Insects 4(4):683-693.

Emergency Department Crowding

It is a well-known problem that crowding and long wait times in the emergency department can increase the health risk for patients. I am currently involved in a working group using queueing theory and stochastic simulation to model the flow of patients through a emergency department. The goal of this project is to provide insights into cost-effective management strategies to increase efficiency and decrease patient waiting times.