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.

KNOW PUBLIC HEALTH EPIDEMIOLOGY   
1)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?

2) 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.
· Percent of drivers found to be legally drunk at the time of their car accident.

3) Suppose that you are following a group of children for the development of asthma over a one- year period. You identify 100 children on January 1st, screen them for asthma, and set up a monitoring program to check on their status on a monthly basis. Five children are considered prevalent cases because they were diagnosed with asthma before January 1st. Ten children develop asthma on March 1st and another ten children develop asthma on July 1st. Another 10 children who remain healthy were followed for six months and then were lost to follow-up. All of the remaining children did not develop asthma and were not lost to follow-up. Follow-up ended on December 31st.
· What was the prevalence of asthma on June 1st?
· What was the prevalence of asthma on September 1st?
· How many person-months of observation were accrued by this population?
· What was the incidence rate of asthma in this population for the one-year period?