In the following years, a significant demographic decline (with peak mortality in years in 1997, 1998 and 2001) was observed, leading to a low post-epidemic density of 1.4 haand/100 ha and a conservative decline estimate of 77%.
Typically, there are many risk factors driving the emergence of the epidemic including population density, degree of transmission, degree of contagion, contact nature, water condition, and climate and so on [13, 14].
We included changes in determinants of infectious disease epidemic dynamics: population density, proportion living in urban areas, and crude birth rate in a given country and year.
Populations naturally cycle between phases of endemic (small, low-density populations attacking low-quality hosts) and epidemic (wide-spread, high-density populations attacking mature healthy trees) (Safranyik and Wilson, 2006) approximately every 20 years (Aukema et al., 2006; Safranyik et al., 2010).
For example, the spatial dynamics of pertussis in Senegal are characterized by a transmission wave from urban centers toward rural areas, which suggests the importance of population size and density in epidemic timing [ 13].
Due to population density, HIV epidemics are often concentrated in main cities and along main roads.
A second mechanism by which rabies may persist is the concept of long incubators, which carry infection through quiescent periods to restart epidemics when the host density has recovered.
However, shortages of trained personnel and other institutional delays meant that spraying could not begin until the third week of June, by which time the epidemic had peaked (and densities of vector mosquitoes had presumably begun to fall).
Subsequent epidemics start only when susceptible density has increased over time via births, resulting in repeated epidemic cycles interspersed with deep troughs of little or no measles incidence [4] (figure S1b).
In this paper we use an individual-based model of disease transmission to assess how an epidemic is influenced by worker density and activity level, the probability of disease transmission, and the structural organization of the nest.
Figure 2 Illustration of the variations of the final infected density and the epidemic threshold with respect to the parameters α and δ.
