Infectious Disease Transmission as a Complex System Process
43 Alderwood Drive, West Hartford, Connecticut, USA
School of Medicine, University of Connecticut Health Center, Farmington, Conn., USA
Last modified: May 28, 2007
The development and transmission of infectious diseases involve complex systems at different levels, and bring together biological, epidemiological, clinical, and public health issues.
We here mainly discuss vector-borne parasitic diseases, in particular, diseases which involve a primary host, a vector, and a parasite. We shall here regard humans as the primary ( or definitive) host and mosquitoes as the vector; the same method applies to other instances of the vector and host. The results shown here are primarily for filariasis, with a comparison to malaria.
We separate out the two primary subsystems – one involving the biology of the disease in a single vector, and the other involving the biology of the disease in a single (human) host. We first model the processes within each separate subsystem, and then the system made up of two such interacting subsystems, which describes the transmission of infection between two humans through a vector.
We then discuss a model at a different level -- for the transmission of infection in a population of vectors interacting with a population of hosts. Besides disease-free and infective states, the model allows for exposed but non-infective states of the host and vector, and for recovered states for the host.
We further discuss (a) the role of the immune system; (b) the effect of different control strategies; and (c) the effects of environmental factors. We discuss special features such as the occurrence of transition points and the role of delays, and point out the complexities inherent in the biological processes.