Lab 2 ID Epi

EPI 5240 – Fall 2023 Lab 2: Infectious disease epidemiology Question 1: There has been an outbreak of acute diarrheal disease in Addis Ababa, Ethiopia. a) Use the data in Table 1 to compute the attack rates and case fatality rates. Table 1. Attack rates and case fatality rates in an acute diarrheal disease outbreak by age and sex in Addis Ababa, Ethiopia, 2017 Number of cases of diarrheal disease Number of diarrheal disease deaths Population Attack rate (%) Case fatality rate (%) Age group (years) Children (0-9) 12 1 105 11.42857143 8.333333333 Young adults (10-19) 23 3 77 29.87012987 13.04347826 Adults (20-59) 125 18 274 45.62043796 14.4 Older adults (≥60) 31 5 56 55.35714286 16.12903226 Sex Male 67 9 246 27.23577236 13.43283582 Female 124 18 266 46.61654135 14.51612903 Overall 191 27 512 37.3046875 14.13612565 b) Briefly summarize your findings from 1(a). Progression of the attack rate increases as one ages. Females have a higher attack rate than males. Case fatality increases as one ages and the case fatality rate is similar for males and females. Overall, 37.7% of popn at risk developed acute diarrgeal disease Among those diagnosed , 14.1% died fmor the disease We can see that both attack rates and case fatality rates increase as the age group increases The attack rate inf emales is much higher when compared to males ( almost as twice high) c) Using the data in Table 2, create an epidemic curve displaying the new cases by date of illness onset. Please make sure to title your graph and label your axes. You may wish to do this in Excel or the statistical software of your choice. 1

EPI 5240 – Fall 2023 0 10 20 30 40 50 60 70 Epidemic curve: Number of cases of acute diarrheal disease by date of illness onset, Addis Ababa, Ethiopia, 2017 Date of illness onset Number of Cases Table 2. Number of cases of acute diarrheal disease by date of illness onset, Addis Ababa, Ethiopia, 2017 Date of illness onset Number of cases 21-Jun-17 1 22-Jun-17 0 23-Jun-17 4 24-Jun-17 12 25-Jun-17 50 26-Jun-17 75 27-Jun-17 23 28-Jun-17 12 29-Jun-17 2 30-Jun-17 3 01-Jul-17 1 02-Jul-17 0 d) Briefly describe what the graph is displaying in terms of the onset and distribution of cases and the type of outbreak it appears to be. This is a point source outbreak where the date of the onset of illness is within a range of less than two weeks and disappears at the end of two weeks , one incubation period of disease. 2

EPI 5240 – Fall 2023 Age group in years 0–9 0 2 25 7.40740741 10–19 2 0 40 0 20–29 26 14 51 21.5384615 30–39 19 6 30 16.6666667 40–49 18 5 21 19.2307692 50–59 19 8 35 18.6046512 60–69 11 5 18 21.7391304 70+ 7 1 18 5.26315789 Total 102 41 238 14.6953405 There was a total of 1-2 primary cases and 279 ocontacts (381-102=279) of whom there were 41 secondary cases Secondary attack rate is 41/279 X100%=14.7% Question 4: After a banquet attended by 100 people, 20 individuals become ill with severe diarrhea. All 100 people are interviewed about their food consumption at the banquet. The interviews show that 15 of the 20 people with severe diarrhea and 12 of the 80 who are healthy ate potato salad. What is the attack rate among those who ate potato salad and those who did not? AR; potato 55.555555 6 AR;no potato 6.8493150 7 Question 5: Using Tables 4 and 5, what are the acute gastroenteritis attack rates in persons who ate both egg salad and tuna, just egg salad, just tuna salad, and neither egg salad or tuna? no tuna tuna Ate salad 80% 75% no salad 30% 35% Question 6: Using Tables 4 and 5, which of the food items (or combination of food items) is most likely to be infective? Egg salad is the infective Table 4. Total number of persons who ate each specified combination of food items Ate tuna Did not eat tuna 4

EPI 5240 – Fall 2023 Ate egg salad 75 100 Did not eat egg salad 200 50 Table 5. Total number of persons who ate each specified combination of food items and who later became sick with acute gastroenteritis Ate tuna Did not eat tuna Ate egg salad 60 75 Did not eat egg salad 70 15 Question 7: Pick an infectious disease and briefly describe its characteristics below (agent, host, environment, reservoir, transmission). Examples of possible information sources could include: World Health Organization, US Centers for Disease Control, Public Health Agency of Canada, etc. Agent : Escherichia coli Host: humans and warm-blooded animals Environment: temperatures ranging from 7 °C to 50 °C, with an optimum temperature of 37 °C. Some STEC can grow in acidic foods, down to a pH of 4.4, and in foods with a minimum water activity (a W ) of 0.95. Reservoir: Cattle Vector: None raw veggies ( foods) , water transmission: oral, (foodborn, waterborne) , contact, fecal Key facts  Escherichia coli (E. coli) is a bacteria that is commonly found in the lower intestine of warm-blooded organisms. Most E.coli strains are harmless, but some can cause serious food poisoning.  Shiga toxin-producing E. coli (STEC) is a bacterium that can cause severe foodborne disease.  Primary sources of STEC outbreaks are raw or undercooked ground meat products, raw milk, and faecal contamination of vegetables.  In most cases, the illness is self-limiting, but it may lead to a life-threatening disease including haemolytic uraemic syndrome (HUS), especially in young children and the elderly. 5