Biology Reference
In-Depth Information
AREAS IN WHICH THE APPOXIMATE
BEGINNING OF THE EPIDEMIC WAS
BEFORE SEPT. 14
BEFORE SEPT. 14 AND SEPT. 21
BEFORE SEPT. 21 AND SEPT. 28
BEFORE SEPT. 28 AND OCT. 5
AFTER OCT. 5
A
140.0
120.0
100.0
80.0
60.0
40.0
20.0
0.0
Sept 14 Sept 21 Sept 28
Oct 5
Oct 12
Oct 19
Oct 26
Nov 2
Nov 9
Nov 16 Nov 23
B
Week of 1918
FIGURE 2-1.
The influenza epidemic of 1918 in the United States. Panel A: Territorial spread of the epidemic from
September to early October 1918; panel B: Death toll in Richmond, VA, attributed to the influenza
and pneumonia. (Panel A is from Crosby, A. W. [1989]. America's forgotten pandemic: The influenza of
1918. Cambridge, UK: Cambridge University Press. Used by permission. Data for panel B were
obtained from the same source.)
II. THE SPREAD OF AN EPIDEMIC
A. Properties of the Mathematical Models
The models in this chapter will be continuous, and their behavior will be
described by coupled differential equations. Typically, there will be two
or more interacting groups and one differential equation per group
describing how that particular group changes. Coupling means that at
