Long‐Distance Dispersal and Accelerating Waves of Disease: Empirical Relationships

Abstract

Classic approaches to modeling biological invasions predict a "traveling wave" of constant velocity determined by the invading organism's reproductive capacity, generation time, and dispersal ability. Traveling wave models may not apply, however, for organisms that exhibit long-distance dispersal. Here we use simple empirical relationships for accelerating waves, based on inverse power law dispersal, and apply them to diseases caused by pathogens that are wind dispersed or vectored by birds: the within-season spread of a plant disease at spatial scales of <100 m in experimental plots, historical plant disease epidemics at the continental scale, the unexpectedly rapid spread of West Nile virus across North America, and the transcontinental spread of avian influenza strain H5N1 in Eurasia and Africa. In all cases, the position of the epidemic front advanced exponentially with time, and epidemic velocity increased linearly with distance; regression slopes varied over a relatively narrow range among data sets. Estimates of the inverse power law exponent for dispersal that would be required to attain the rates of disease spread observed in the field also varied relatively little (1.74-2.36), despite more than a fivefold range of spatial scale among the data sets.

Unifying the spatial epidemiology and molecular evolution of emerging epidemics

“…3B). This acceleration rate, estimated solely from viral genomic data, is almost identical to that independently estimated from large-scale patterns of spatiotemporal WNV incidence (31). Such acceleration is theoretically predicted to occur when there is high variance in dispersal among infected hosts-specifically, when the dispersal kernel is positively skewed and "fat-tailed" (32).…”

The coffee rust crises in Colombia and Central America (2008–2013): impacts, plausible causes and proposed solutions

“…Meaning of damage categories: 1, no damage; 2, low damage (defoliation substantially below 50 %), 3, moderate damage (defoliation around 50 %); 4, severe damage (defoliation substantially above 50 %). Data on 1224 farms in 2012 and information on first foci in 2011 were provided by ANACAFE The progress of coffee rust at this almost continental scale seems to follow the expected pattern for long distance dispersal diseases (Mundt et al 2009), where epidemic velocity increases with distance from the initial source. This observation indicates that wind probably played a key role in coffee rust spread, although the disease is already present in all of the coffee growing countries and possibly in all of the susceptible coffee plots of Mesoamerica.…”

Wet climate and transportation routes accelerate spread of human plague

“…Transmission of pandemic diseases is often classified into contact and relocated diffusions which are caused, respectively, by short-and long-distance transmissions [8][9][10][11][12]. Contact diffusion refers to the short-distance spread of a disease outward from a central focus continuously in space.…”