Epi-500 Exercises Answer Key Supplemental Exercises PDF

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EPI-500-Section 2 Supplemental Exercises Exercise 1.1 Below are four key terms taken from the definition of epidemiology, followed by a list of activities that an epidemiologist might perform. Match the term to the activity that best describes it. You should match only one term per activity. A. Distribution B. Determinants C. Application ___B__ 1. Compare food histories between persons with Staphylococcus food poisoning and those without ___B__ 2. Compare frequency of brain cancer among anatomists with frequency in general population ___A__ 3. Mark on a map the residences of all children born with birth defects within 2 miles of a hazardous waste site ___A__ 4. Graph the number of cases of congenital syphilis by year for the country ___C__ 5. Recommend that close contacts of a child recently reported with meningococcal meningitis receive Rifampin ___A__ 6. Tabulate the frequency of clinical signs, symptoms, and laboratory findings among children with chickenpox in Cincinnati, Ohio Exercise 1.2 In August 1999, epidemiologists learned of a cluster of cases of encephalitis caused by West Nile virus infection among residents of Queens, New York. West Nile virus infection, transmitted by mosquitoes, had never before been identified in North America. Describe how this information might be used for each of the following: The goals of this exercise what to keep in mind the 4 aims and levels of epidemiology: Describe, Explain, Predict, and Control. 1. Assessing the community’s health Since cases are new (have never been before identified here in North America), public health workers must assess the health of the community. Relevant questions that may be: - Is the cluster limited to persons who have just returned from traveling where West Nile virus infection is common, - Was the infection acquired locally, indicating that the community is truly at risk? Public health must use surveillance methods (e.g., sentinel or syndromic) to check whether hospitals have seen more patients than usual for encephalitis 2. Making decisions about individual patients West Nile virus infection is spread by mosquitoes. Persons who spend time outdoors, Particularly at times such as dusk when mosquitoes may be most active, can make personal decisions to reduce their own risk or not. Protective measures to prevent mosquito bites: wear long pants and long-sleeve shirts even though it is August, or empty the bird bath where mosquitoes breed. 3. Documenting the clinical picture of the illness Investigators need to assess infection, and ask patients and provides about symptoms and illness being experienced. In addition, what becomes of the persons who did develop Courtesy of the CDC and other Epidemiology Sources

EPI-500-Section 2 Supplemental Exercises encephalitis? What proportion survived? Did they recover completely or did some have continuing difficulties? 4. Searching for causes to prevent future outbreaks Public health officials asked many questions regarding how the virus was Introduced (mosquito on an airplane? wayward bird? bioterrorism?), whether the virus had a reservoir in the area (e.g., birds), what types of mosquitoes could transmit the virus, what were the host risk factors for infection or encephalitis, etc. Exercise 1.3 For each of the following situations, identify whether it reflects: A. Sporadic disease B. Endemic disease C. Pandemic disease D. Epidemic disease Epidemic_ 1. 22 cases of legionellosis occurred within 3 weeks among residents of a particular neighborhood (usually 0 or 1 per year) Key: 22 cases vs. usually 0 or 1 per year. Clearly 22 surpasses the normal expectancy (which is the definition of epidemic) Pandemic_ 2. Over 20 million people worldwide died from influenza in 1918—1919 Key: Crossing international borders, occurring globally Sporadic_ 3. Single case of histoplasmosis was diagnosed in a community Key: Once single case Endemic_ 4. About 60 cases of gonorrhea are usually reported in this region per week, slightly less than the national average Key: slightly less than national average (note how this is localized by this region) Exercise 1.4 For each of the trends in disorders, describe and identify examples of primary, secondary, and tertiary levels of prevention. Disorder trends: - Disappearing: Smallpox, polio, measles - Residual: Sexually transmitted infections, tobacco use, infant mortality - Persisting: Cancer, mental disorders, Cerebrovascular disease - New Epidemic: Lung cancer, HIV/AIDS, Obesity. Levels of prevention: Refer to the chart below to come up with primary, secondary, and tertiary levels of prevention identified above.

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EPI-500-Section 2 Supplemental Exercises -

Exercise 1.5 Go to the U.S. Census Bureau’s Website or any Country’s Census Data and describe the population trend for years 1980, 1990, 2000, and 2010. What can you conclude from the age distribution by gender? Describe the population of the US by each time using age and sex as reference.

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EPI-500-Section 2 Supplemental Exercises

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EPI-500-Section 2 Supplemental Exercises

Exercise 1.6

Which of the following criterion for causality match the statements below? a) “We examined the relationship between television viewing and initiation of smoking and found a strong doseresponse relationship with increasing hours.” (Biological Gradient) b) “In this study, television viewing was measured 2 years before smoking initiation.” (Temporality) c) “The association was substantial, with youth who watched >5 hours per day being 5.99 times as likely to initiate smoking than youth who watched 0 to 2 hours per day.” (Strength of Association) d) “…Television provides adolescents with role models, including movie and television stars and athletes, who portray smoking as a personally and socially

rewarding behavior.” (Biological Plausibility) e) “The findings are consistent with social learning theory.” (Coherence) f) “A similar association between television viewing and the onset of alcohol use has been reported…” (Analogy) 1) 2) 3) 4) 5) 6) 7) 8) 9)

Strength of Association Consistency Analogy Biological Gradient Plausibility Experiment Temporality Coherence Specificity

Exercise 1.7 Calculating a Ratio, Proportions — Different Categories of Same Variable Between 1971 and 1975, as part of the National Health and Nutrition Examination Survey (NHANES), 7,381 persons ages 40–77 years were enrolled in a follow-up study.1 At the time of enrollment, each study participant was classified as having or not having diabetes. During 1982–1984, enrollees were documented either to have died or were still alive. The results are summarized as follows.

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EPI-500-Section 2 Supplemental Exercises

Diabetic Men Nondiabetic men Diabetic women Nondiabetic Women

Original Enrollment 189 3,151 218 3,823

Dead at Follow Up 100 811 72 511

Calculate the ratio of non-diabetic to diabetic men. Non Diabetic Men/ Diabetic Men = (3,151 / 189) = 16.7 non diabetic men to 1 diabetic man. Calculate the ratio of non-diabetic women to diabetic women. Non Diabetic Women/ Diabetic Women = (3,823 / 218) = 17.53 non diabetic women to 1 diabetic woman. Calculate the proportion of men in the NHANES follow-up study who were diabetics Numerator = 189 diabetic men Denominator = Total number of men = 189 + 3,151 = 3,340 Proportion = (189 / 3,340) x 100 = 5.66% What proportion of all study participants were men? Numerator = Total number of men = Diabetes and no diabetic men = (189 + 3,151) = 3,340 Denominator = Total participants of NHANES = 7,381. Proportion = (3,340 / 7,381) x 100 = 45.25% Exercise 1.8 Calculate the following rates: Incident Rate from October 1, 1990 to September 30, 1991 Point prevalence on October 1, 1990 and Period prevalence, October 1, 1990 to September 30, 1991 Calculate the incidence density for the whole time period

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EPI-500-Section 2 Supplemental Exercises

Calculate the incidence rate from October 1, 1990, to September 30, 1991, using the midpoint population (population alive on April 1, 1990) as the denominator. Express the rate per 100 population. Incidence rate = (4 / 18) x 100 = 22 new cases per 100 populations Incidence rate numerator = number of new cases between October 1 and September 30 = 4 (the other 6 all had onsets before October 1, and are not included) Incidence rate denominator = April 1 population = 18 (persons 2 and 8 died before April 1) Example B: Calculate the point prevalence on April 1, 1990. Point prevalence is the number of persons ill on the date divided by the population on that date. On April 1, seven persons (persons 1, 4, 5, 7, 9, and 10) were ill. Point prevalence = (7 / 18) x 100 = 38.89% Example C: Calculate the period prevalence from October 1, 1990, to September 30, 1991. The numerator of period prevalence includes anyone who was ill any time during the period, the first 10 persons were all ill at some time during the period. Period prevalence = (10 / 20) x 100 = 50.0%

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EPI-500-Section 2 Supplemental Exercises

Incidence density for the whole time period Number of new cases / Total person time at risk Calculating person time (in months) Person 3 = 0.2 Person 4 = 1.2 Person 6 = 1 ` Person 7 = 1.5 Person 10 = 1.5 Total person time = 5.4 New cases = 4 Incidence density = 4/5.4 person moth = 0.70 cases per person-month. Exercise 1.9 Two surveys were done of the same community 12 months apart. Of 5,000 people surveyed the first time, 25 had antibodies to histoplasmosis. Twelve months later, 35 had antibodies, including the original 25. We will calculate the prevalence at the second survey, and compare the prevalence with the 1-year incidence. Calculate the Prevalence at the second survey: Prevalence at the second survey: x = antibody positive at second survey = 35 y = population = 5,000 (x/y) x 10ⁿ = 35/5,000 x 1,000 = 7 per 1,000 Calculate the Incidence during the 12 month period Incidence during the 12-month period: x = number of new positives during the 12-month period = 35 – 25 = 10 y = population at risk = 5,000 – 25 (already infected) = 4,975 (x/y) x 10n = 10/4,975 x 1,000 = 2 per 1,000 Prevalence is based on both incidence (risk) and duration of disease. High prevalence of a disease within a population may reflect high risk, or it may reflect prolonged survival without cure. Conversely, low prevalence may indicate low incidence, a rapidly fatal process, or rapid recovery.

Exercise 1.10 Courtesy of the CDC and other Epidemiology Sources

EPI-500-Section 2 Supplemental Exercises

All Races, Both Sexes Age Group (years)

All Causes

Unintentional Injuries

All Races, Males

Estimated Pop (x 1000)

All Causes

Unintentional Injuries

Estimated Population (x 1000)

0-4

32,892

2,857

19,597

18,523

1,577

10,020

5–14

7,150

2,718

41,037

4,198

1713

21,013

15-24

33,046 15

15,412

40,590

24,416

11,438

20,821

25-34

41,355

12,569

39,928

28,736

9,635

20,203

35-44

91,140

16,710

44,917

57,593

12,012

22,367

45-54

172,385

14,675

40,084

107,722

10,492

19,676

55-64

253,342

8,345

26,602

151,363

5,781

12,784

65+

1,811,720

33,641

35,602

806,431

16,535

14,772

357

85

0

282

74

0

2,443,387

106,742

288,357

1,199,264

69,257

141,656

Not Stated Total

Given the information provided in the table, Calculate: a) Unintentional-injury-specific mortality rate for the entire population This is a cause-specific mortality rate. Rate = number of unintentional injury deaths in the entire population x 100,000 Estimated midyear population = (106,742 / 288,357,000) x 100,000 = 37.0 unintentional-injury-related deaths per 100,000 populations b) All-cause mortality rate for 25–34 year olds All-cause mortality rate for 25–34 year olds This is an age-specific mortality rate. Rate = number of deaths from all causes among 25–34 year olds x 100,000 estimated midyear population of 25–34 year olds = (41,355 / 39,928,000) x 100,000 = 103.6 deaths per 100,000 25–34 year olds c) All-cause mortality among males All-cause mortality among males This is a sex-specific mortality rate.

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EPI-500-Section 2 Supplemental Exercises Rate = number of deaths from all causes among males x 100,000 estimated midyear population of males = (1,199,264 / 141,656,000) x 100,000 = 846.6 deaths per 100,000 males d) Unintentional-injury specific mortality among 25 to 34 year old males Unintentional-injury specific mortality among 25 to 34 year old males This is a cause-specific, age-specific, and sex-specific mortality rate Rate = number of unintentional injury deaths among 25–34 year old males x 100,000 estimated midyear population of 25–34 year old males = (9,635 / 20,203,000) x 100,000 = 47.7 unintentional-injury-related deaths per 100,000 25–34 year olds Exercise 1.11 In 2001, a total of 15,555 homicide deaths occurred among males and 4,753 homicide deaths occurred among females. The estimated 2001 midyear populations for males and females were 139,813,000 and 144,984,000, respectively. 1. Calculate the homicide-related death rates for males and for females. Homicide-related death rate (males) = (# homicide deaths among males / male population) x 100,000 = 15,555 / 139,813,000 x 100,000 = 11.1 homicide deaths / 100,000 population among males Homicide-related death rate (females) = (# homicide deaths among females / female population) x 100,000 = 4,753 / 144,984,000 x 100,000 = 3.3 homicide deaths / 100,000 population among females 2. What type(s) of mortality rates did you calculate in Question 1? These are cause- and sex-specific mortality rates. 3. Calculate the ratio of homicide-mortality rates for males compared to females. Homicide-mortality rate ratio = homicide death rate (males) / homicide death rate (females) = 11.1 / 3.3 = 3.4 to 1 4. Interpret the rate you calculated in Question 3 as if you were presenting information to a policymaker. Because the homicide rate among males is higher than the homicide rate among females, specific intervention programs need to target males and females differently. Exercise 1.12

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EPI-500-Section 2 Supplemental Exercises In Missouri in 2004, a total of 127 HIV-related deaths occurred in males and 17 HIV-related deaths occurred in females. The estimated 2004 midyear population in Missouri was 2,810,852 males and 2,943,766 females. Calculate the HIV-related death rate for males and for females. HIV-related death rate for males x = male deaths = 127 y = male population = 2,810,852 x/y x 100,000 = 4.5 per 100,000 population year HIV-related death rate for females x = female deaths = 17 y = female population = 2,943,766 x/y x 100,000 = 0.5 per 100,000 per population year What type of mortality rates did you calculate in step a? Gender-specific mortality rate Calculate the HIV-mortality rate ratio for males versus females. HIV-mortality rate ratio for males versus females x = HIV mortality rate for males y = HIV mortality rate for females x/y x 1 = 4.5 / 0.5 = 9:1 Exercise 1.13 The observed death in 14 in community XYZ Note the numbers may be unrealistic. This was only meant for you to get a better understanding of what was asked of you. Age group

Reference rate

Observed person-time

Expected deaths (per 100,000)

15-24

0.000006

1080

(0.000006 x 1080) = 0.00648

25-34

0.000013

12860

(12860 x 0.000013) = 0.16718

35-44

0.000047

11510

(11510 x 0.000047) = 0.54097

45-54

0.000162 0.000271

10330 7790

(10330 x 0.000162) = 1.67346 (0.000271 x 7790) = 2.11109 Total = 4.49918

55-64

Given this information above, a) Which method of adjustment is appropriate to use? Indirect method of adjustment is appropriate to use given the standard population is not known. b) Calculate the expected deaths and the adjusted death rate Total expected deaths = 4.44918

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EPI-500-Section 2 Supplemental Exercises c) Can you find and interpret the Standardized Mortality Rate? SMR = Observed / Expected = 14/4.44918 = 3.14 A ratio greater than 1.0 indicates that more mortality has occurred than would have been expected. An SMR

Exercise 1.14 Read: Severe Respiratory Illness Associated with Enterovirus D68 — Missouri and Illinois, 2014 Weekly September 12, 2014 / 63(36);798-799 (http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6336a4.htm?s_cid=mm6336a4_w) 1) Describe the Enterovirus D68 by person, place, and time Person: Children are more prone to Enterovirus D68 Place: Geographically localized in the midwest (Chicago, Kansas City) Time: Secular Time trend 2) Generate an analytic null and alternative hypothesis Null: Patients examined and hospitalized with severe respiratory illness present same characteristics (same age, same gender) in hospitals in Chicago and hospitals in Kansas city Alternative: Patients examined and hospitalized with severe respiratory illness present different characteristics (age, and gender) in hospitals in Chicago and hospitals and Kansas city

Exercise 1.15 State funding for a childhood asthma program has just become available. To initiate surveillance for childhood asthma, the staff is reviewing different sources of data on asthma. Discuss the advantages and disadvantages of the following sources of data and methods for conducting surveillance for asthma. (Figure 5.12 indicates national data for these different sources.)  Self-reported asthma prevalence and asthmatic attacks obtained by a telephone survey of the general population.  Asthma-associated outpatient visits obtained from periodic surveys of local health-care providers, including emergency departments and hospital outpatient clinics.  Asthma is a chronic illness that can vary in severity. Using just one source of data or just one dataset to monitor it provides limited knowledge of its extent and the potential effect of treatment and other interventions on it. Thus, using multiple sources of data with information on asthma'sincidence, prevalence, morbidity, and mortality is the best way to conduct surveillance for this illness. - Self-reported asthma prevalence or attacks provides information on its occurrence among the entire population, even those who might not seek or receive medical care for it. - The majority of cases of asthma requiring medical attention are observed in physician offices, emergency departments, or outpatient clinics. Thus, obtaining information from these sources provides optimal knowledge of its occurrence and morbidity among the majority of persons. Courtesy of the CDC and other Epidemiology Sources

EPI-500-Section 2 Supplemental Exe...