<b>Chapters 2-4 </b><br/><b>Which of the following is a condition which may occur during the incubation period? </b><br/>Transmission of infection <br/><b>Chicken pox is a highly communicable disease. It may be transmitted by direct contact with a person <br/>infected with the varicella-zoster virus (VZV). The typical incubation time is between 10 to 20 days. A <br/>boy started school 2 weeks after showing symptoms of chicken pox including mild fever, skin rash, & <br/>fluid-filled blisters. One month after the boy returned to school, none of his classmates had been <br/>infected by VZV. The main reason was: </b><br/>Contact was after infectious period <br/><b>The ability of a single person to remain free of clinical illness following exposure to an infectious agent <br/>is known as: </b><br/>Immunity <br/><b>Which of the following is characteristic of a single-exposure, common-vehicle outbreak? </b><br/>The epidemic curve has a normal distribution when plotted against the logarithm of time <br/><b>What is the diarrhea attack rate in persons who ate both ice cream & pizza? </b><br/>39/52 <br/><b>What is the overall attack rate in persons who did not eat ice cream? </b><br/>33% <br/><b>Which of the food items (or combination of items) is most likely to be the infective item(s)? </b><br/>Ice cream only <br/><b>Which of the following reasons can explain why a person who did not consume the infective food item <br/>got sick? </b><br/> They were directly exposed to persons who did eat the infective food item <br/> Diarrhea is a general symptom consistent with a number of illnesses <br/> There may have been an inaccurate recall of which foods were eaten (all of the above) <br/><b>An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of 846. Fifty-<br/>seven students reported symptoms including vomiting, diarrhea, nausea, & low-grade fever between <br/>10 p.m. on September 24 & 8 p.m. on September 25. The ill students lived in dormitories that housed <br/>723 of the students. The table below provides information on the number of students per type of <br/>residence & the number reporting illnesses consistent with the described symptoms & onset time. <br/>Calculate the attack rate among all students at the boarding school. </b><br/>The answer is found by dividing the total number of cases (57) by the total number of students (846). <br/>This equals 6.7%. <br/><b>An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of 846. Fifty-<br/>seven students reported symptoms including vomiting, diarrhea, nausea, & low-grade fever between <br/>10 p.m. on September 24 & 8 p.m. on September 25. The ill students lived in dormitories that housed <br/>723 of the students. The table below provides information on the number of students per type of <br/>residence & the number reporting illnesses consistent with the described symptoms & onset time. <br/>Calculate the attack rates for boys & girls separately. </b><br/>For boys, the attack rate includes all cases (40 + 3) divided by the total number of students who are boys <br/>(380 + 46). The attack rate is 10.1%. For girls, the attack rate includes all cases (12 + 2) divided by the total number of students who are girls <br/>(343 + 77). The attack rate is 3.3%. <br/><b>An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of 846. Fifty-<br/>seven students reported symptoms including vomiting, diarrhea, nausea, & low-grade fever between <br/>10 p.m. on September 24 & 8 p.m. on September 25. The ill students lived in dormitories that housed </b><br/><b>723 of the students. The table below provides information on the number of students per type of <br/>residence & the number reporting illnesses consistent with the described symptoms & onset time. <br/>What is the proportion of total cases occurring in boys? </b><br/>The proportion of cases occurring in boys is equal to the number of cases in boys divided by the total <br/>number of cases (43/57). This equals 75.4%. <br/><b>An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of 846. Fifty-<br/>seven students reported symptoms including vomiting, diarrhea, nausea, & low-grade fever between <br/>10 p.m. on September 24 & 8 p.m. on September 25. The ill students lived in dormitories that housed <br/>723 of the students. The table below provides information on the number of students per type of <br/>residence & the number reporting illnesses consistent with the described symptoms & onset time. <br/>What is the proportion of total cases occurring in students who live in dormitories? </b><br/>The proportion of cases occurring in dormitory residents is equal to the number of cases in residents <br/>divided by the total number of cases (52/57). This equals 91.2%. <br/><b>An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of 846. Fifty-<br/>seven students reported symptoms including vomiting, diarrhea, nausea, & low-grade fever between <br/>10 p.m. on September 24 & 8 p.m. on September 25. The ill students lived in dormitories that housed <br/>723 of the students. The table below provides information on the number of students per type of <br/>residence & the number reporting illnesses consistent with the described symptoms & onset time. <br/>Which proportion is more informative for the purpose of the outbreak investigation? </b><br/>Both proportions are useful. Dormitory residents account for over 90% of the cases indicating an <br/>outbreak of an infectious agent that was transmitted at the school. Furthermore, over 75% of the cases <br/>were boys indicating that the responsible agent was more likely to have been transmitted in the boys’ <br/>dormitory. <br/><b>A group of researchers are interested in conducting a clinical trial to determine whether a new <br/>cholesterol-lowering agent was useful in preventing coronary heart disease (CHD). They identified <br/>12,327 potential participants for the trial. At the initial clinical exam, 309 were discovered to have <br/>CHD. The remaining subjects entered the trial & were divided equally into the treatment & placebo <br/>groups. Of those in the treatment group, 505 developed CHD after 5 years of follow-up while 477 <br/>developed CHD during the same period in the placebo group. What was the prevalence of CHD at the <br/>initial exam? </b><br/>The prevalence of CHD at the initial exam was 309 cases of CHD divided by 12,327 participants. This <br/>equals a prevalence of 25.1 cases of CHD per 1,000 persons. <br/><b>A group of researchers are interested in conducting a clinical trial to determine whether a new <br/>cholesterol-lowering agent was useful in preventing coronary heart disease (CHD). They identified <br/>12,327 potential participants for the trial. At the initial clinical exam, 309 were discovered to have <br/>CHD. The remaining subjects entered the trial & were divided equally into the treatment & placebo <br/>groups. Of those in the treatment group, 505 developed CHD after 5 years of follow-up while 477 <br/>developed CHD during the same period in the placebo group. What was the incidence of CHD during <br/>the 5-year study? </b><br/>