Outbreaks were actively investigated and efforts were made to identify and describe
such events. The close contacts of those affected were vaccinated, and various
epidemiological measures were taken to interrupt transmission of the virus. Incidence
data from several locations within Africa were reported to the Centers for Disease
Control and Prevention (CDC) in the United States. Weekly update from CDC was
circulated to all active surveillance sites in Africa so that rapid prevention measures
could be taken. With the same staff involved in both the active surveillance and mass
vaccination programs, the effect of these combined actions had a positive impact on
disease transmission. The incidence rate not only decreased drastically, but the seasonal
variation also decreased, with the WHO certifying the eradication of smallpox
in 1980 (WHO, 2010b). The effects of these epidemiological control efforts on a
mass scale are noted in “West and Central Africa Small Pox Eradication Program”
(Foege, Millar, & Lane, 1971).