Epidemiology for Public Health Practice 5th Edition by Robert Friis,Thomas Sellers

Exercise 11

Sharpen your skills in interpreting charts. Figure 1 is a chart that shows data on rabies for 1975 through 2005. The x -axis (abscissa) is the horizontal axis. The y -axis (ordinate) is the vertical axis.
a. What are the labels of the x and y axes?
b. Describe the overall trends reflected in the chart.
c. Why does the line for domestic animals diverge from that of wild animals?
d. What type of disease is rabies?

Periods of resurgence and decline of rabies incidence are primarily the result of cyclic reemergence. As populations are decimated by epizootics, numbers of reported cases decline until populations again reach levels to support epizootic transmission of disease. Recent declines in the number of reported cases among terrestrial reservoir species (raccoons, skunks, and foxes) have been offset by increases in testing and the subsequent detection of rabid bats. In addition, interventions such as the oral vaccination of wildlife species might contribute to the decreasing trend in recent years.
Figure 1 Rabies, number of reported cases among wild and domestic animals,* by year-United States and Puerto Rico, 1975-2005.
Source: Reproduced from Centers for Disease Control and Prevention, Summary of notifiable diseases-United States, 2005, MMWR , Vol 54, No. 53, p. 63, 2007. *Data from the National Center for Zootic, Vector-Borne, and Enteric Diseases (proposed).