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About the Authors:
Michael A. Johansson
* E-mail: [email protected]
Affiliation: Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, San Juan, Puerto Rico, United States of America
Neysarí Arana-Vizcarrondo
Affiliation: Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, San Juan, Puerto Rico, United States of America
Brad J. Biggerstaff
Affiliation: Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America
J. Erin Staples
Affiliation: Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America
Nancy Gallagher
Affiliation: Division of Global Migration and Quarantine, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
Nina Marano
Affiliation: Division of Global Migration and Quarantine, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
Introduction
The global airline network has brought the entire world closer together than ever before, creating an environment in which pathogens can readily spread to distant locations. Influenza viruses are perhaps the most widely recognized example of this phenomena [1], [2], but by no means the only one [3], [4], [5]. Study of past spread and discussion about potential mitigation efforts has lead to a significant body of literature investigating the use of mathematical models to predict global pathogen spread and to assess the potential effectiveness of various interventions [3], [6], [7], [8], [9], [10], [11], [12], [13].
These models are generally framed as metapopulation models, with spatially discrete populations connected by transportation networks. The discrete populations themselves are subdivided in terms of infection status with compartments for susceptible, incubating, infectious, and recovered individuals. Development of these models presents many challenges related to the characterization of the populations, the disease, and relevant travel patterns. We focus here on oft-neglected assumptions related to the characterization of travel which may affect the speed and pattern of epidemic growth and spread.
One fundamental assumption in many models is that travelers are, in essence, migrants; people who move permanently or semi-permanently from one geographic population to another [3], [6], [7], [8], [9], [10], [11], [12], [13]. In the real world, some travelers are migrating, but for most, travel is temporary. For example, each year there are approximately 175 million total admissions to the United States and...