QUESTION 1

Which type of measure of disease frequency best describes each of the following scenarios?

• Percentage of students enrolled in a college who developed influenza during the spring semester of 2012.
• Percentage of students enrolled in an epidemiology class who had sore throats on the first day of class.
• Percent of breast cancer patients who underwent mastectomy during 2012.
• Percent of men found to have high blood pressure at their yearly physical.
• Number of newly-diagnosed cases of AIDS in a year per 100,000 persons.
• Percent of infants born with spina bifida out of 1,000 liveborn infants.
• Percentofdriversfoundtobelegallydrunkatthetimeoftheircaraccident.

QUESTION 2

A population of 1,000 people is monitored for a year for the development of measles. No one has measles at the start of the investigation. Thirty people develop measles on June 30 and twenty people develop measles on September 30. Eight people are lost to follow-up on March 31 and twenty-four people are lost to follow-up on November 30. None of those lost to follow-up had developed measles prior to becoming lost. Assume that you can only get measles once.

• What is the cumulative incidence of measles in this population?
• What is the incidence rate of measles?
• WhatistheprevalenceofmeaslesonJuly1?

QUESTION 3

How does each of the following conditions influence the prevalence of a disease in a population? For each scenario, assume that no other changes occur. Your choices are: increases prevalence, decreases prevalence, or has no effect on prevalence.

A treatment is developed that prolongs the life of people suffering from the disease

A new measure is developed that prevents new cases of disease from occurring

There is immigration of a large number of healthy people into the population.

The case-fatality rate for the disease increases