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Inquiry Activity • Paper and Pencil

Chapter 9 Tracking an Outbreak

Problem How can an outbreak of cholera begin and how can it spread?

Background

Disease Hunters

Epidemiologists are disease hunters. They study the causes of diseases and how they spread. When a new disease appears or when the number of cases of a disease suddenly increases, epidemiologists try to determine why the outbreak is happening and find ways to bring it under control. By interviewing patients, their families, and anyone the patients may have come in contact with, epidemiologists look for patterns in the disease outbreak. They may plot cases and their details on a map to determine whether the cases cluster around a possible source of the disease.

A Cholera Epidemic

Suppose that doctors in the United States see an increase in the number of cases of cholera, a potentially life-threatening intestinal disease caused by bacteria. Seventy-seven cases are reported in eight cities between July 5 and July 25. Interviews with the patients reveal that all of them ate oysters shortly before becoming ill. Officials suspect that these oysters were contaminated and were sold without being properly inspected. Suppose you are an epidemiologist given the job of analyzing the case for clues. Use the data table to determine how the outbreak began and spread, and whether it is increasing or decreasing.

|Distribution of Cholera Cases |

|City |Outbreak Period |Number of Cases |

|Houston, Texas |July 5–15 |14 |

|Louisville, Kentucky |July 10–20 |8 |

|Memphis, Tennessee |July 8–18 |14 |

|Minneapolis, Minnesota |July 13–23 |4 |

|New Orleans, Louisiana |July 6–16 |13 |

|Pittsburgh, Pennsylvania |July 15–25 |2 |

|St. Louis, Missouri |July 11–21 |10 |

|St. Petersburg, Florida |July 6–16 |12 |

[pic] Build Map Skills

Locating Cities on a Map Many maps show political boundaries—the outlines of countries or states. Some maps also show geographic features, such as major bodies of water, rivers, and mountains, and so forth. Maps can also show political features, such as large cities. However, the map below does not show cities. Using an atlas, mark the locations of the cities listed in the data table. Follow these steps:

• Find the state in which the city is located.

• Find out where the city is located in the state.

• Mark the city on your map, shown below. Mark it with a dot and label it.

1. Use the map below to locate and label the eight cities in which cholera cases have appeared. Write each city’s name along with the dates of the outbreak and the number of cases in that city.

|Political Boundaries of Contiguous United States |

|[pic] |

Look for patterns in the dates, number of cases, duration of the outbreak, and relative locations of the affected cities.

Some of the questions you should think about as you analyze the outbreak:

• When and where were the oysters harvested?

• How did the oysters get to the cities where cholera occurred?

• Did the outbreak last as long in each city?

• Is the number of new cases of cholera increasing or decreasing?

Analyze and Conclude

2. Analyze Data What patterns in dates, number of cases, duration of the outbreak, and relative locations of the affected cities did you notice?

3. Compare and Contrast Is the number of cases increasing or decreasing as the disease spreads? Explain how the data from two specific cities support your answer.

4. Form a Hypothesis Propose a hypothesis to explain how the cholera outbreak may have started.

5. Draw Conclusions Based on the data, how do you account for the sequence in which the outbreaks occurred in the different cities? Explain your answer.

6. Extension Do you think the cholera outbreak will continue to spread? If so, where might the next cases of cholera be reported? Explain your answer.

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