1. The population of a city on February 15, 2005, was 36,600. The city has a passive surveillance system that collects hospital and private physician reports of influenza cases every month. During the period between January 1 and April 1, 2005, 2,200 new cases of influenza occurred in the city. Of these cases, 775 persons were ill with influenza according to surveillance reports on April 1, 2005. The prevalence rate of active influenza as of April 1, 2005, was: Answer: 20 per 1,000 population 2. The population of a city on February 15, 2005, was 36,600. The city has a passive surveillance system that collects hospital and private physician reports of influenza cases every month. During the period between January 1 and April 1, 2005, 2,200 new cases of influenza occurred in the city. Of these cases, 775 persons were ill with influenza according to surveillance reports on April 1, 2005. The monthly incidence rate of active cases of influenza for the 3-month period was: Answer: 20 per 1,000 population 3. What would be the effect on age-specific incidence rates of uterine cancer if women with hysterectomies were excluded from the denominator of incidence calculations assuming that most women who have had hysterectomies are older than 50 years of age? Answer: Rates would increase in women older than 50 years of age but may decrease in younger women as they get older. 4. The ability of a single person to remain free of clinical illness following exposure to an infectious agent is known as: Answer: Immunity 5. Which of the following reasons can explain why a person who did not consume the infective food item got sick? Answer: All of the above 6. Which of the food items (or combination of items) is most likely to be the infective item(s)?