Centers for Disease Control and Prevention – Epidemiology Program Office
Case Studies in Applied Epidemiology No. 711-903 – Student’s Guide (Interactive Version)
After completing this case study, you should be able to:
On Tuesday, November 3, 1970, the Center for Disease Control (CDC) in Atlanta received the weekly telegram of surveillance data from the Texas State Health Department. The telegram reported 319 cases of measles in the state during the previous week. In contrast, Texas had reported an average of 26 cases per week during the previous four weeks.
In follow-up telephone calls, CDC learned from State health officials that 295 cases of measles had been diagnosed in the city of Texarkana, including 25 in children reported to have been previously immunized.
An invitation to investigate the situation was extended to the CDC on November 4, 1970. An EIS officer departed for Texarkana early on November 5.
Texarkana is a city of roughly 50,000 that straddles the Texas–Arkansas state line.
Although Texarkana is divided by the state line, it is a single town economically and socially. Persons of all ages on both sides of town have frequent contact. Churches, physicians’ offices, movie theatres, and stores draw people from both the Arkansas and Texas sides of town. People cross the state line to attend social functions such as football games and school dances. Many families have friends and relatives who visit back and forth on both sides of town. Private nurseries and kindergartens receive children from both sides of town. However, the two sides of Texarkana have separate public school systems and separate public health departments.
List the reasons to investigate a suspected outbreak. Which reasons may have prompted an investigation of this outbreak?
What would be the initial steps of your investigation, i.e., the steps before trying to find additional cases?
How might you look for additional cases?
Once you collected information about the cases, how would you characterize the outbreak?
The investigators obtained names of cases from the health departments, physicians, school and nursery records. They conducted a door-to-door survey and also asked families of cases for names of other cases. They used the same methods of case-finding and epidemiologic investigation on both the Arkansas and Texas sides of town.
The illness was clinically compatible with measles. Typically, the patients had a 4- to 5-day prodrome with high fever, coryza (runny nose), cough, and conjunctivitis (red, irritated eyes) followed by the appearance of a bright maculopapular (red spots and areas) rash. The temperature usually returned to normal 2 to 3 days after appearance of the rash, while the rash persisted for 5 to 7 days.
How might you define a case for purposes of this investigation?
Describe the difference between a sensitive case definition and a specific case definition. What are the advantages and disadvantages of each? Provide an example of a situation where each would be helpful.
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