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Chapter 6

Infectious Disease Epidemiology
  1. Give reasons why crowding can foster the spread of infection.

  2. Figure 6–1 displays crude death rates over time. The age distribution of the population was changing over the time scale shown, gradually shifting toward an older age distribution. If age had been controlled so that the curve reflected the change in death rates among people with the same age distribution, would the curve drop more steeply or less steeply than what is shown in Figure 6–1? Comment on the apparent rise in the crude death rate in the past 15 years covered by the graph.

  3. Explain the relation between quarantine and the effective reproductive number.

  4. The Reed-Frost model is a simplified model of transmission that assumes the population is closed. Suppose that with each generation time there is some migration into and out of the population. Under what conditions would that mixing hasten the transmission of disease, and under what conditions would it slow the transmission?

  5. Varicella infection (chicken pox) results in long-term immunity to the virus that causes it, but infected people can experience a recrudescence of their infection, known as shingles, years or decades after their initial infection. How does the virus persist in the body over such a long period despite an immune system that is primed to deactivate the virus with specific antibodies?

  6. Despite evidence of person-to-person spread, contact tracing was not widely used to control the spread of HIV in the early stages of the epidemic. Give pro and con arguments regarding the desirability of contact tracing to contain the transmission of HIV.

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