Title: Default for Step 1.18 Basic case reproduction number and secondary attack rate - Quiz

Q: How would you expect R_0 for Ebola in an urban area to compare with the R0 for Ebola in a rural area?
- R_0 would probably be higher in an urban area (The infectious case is likely to have contact with more people in an urban population than in a rural population, so R_0 is likely to be higher.)
- R_0 would probably be higher in a rural area (Think about the likely number of effective contacts between people in urban vs rural settings. You may find 1.17 Transmissibility: how do we measure infectiousness? useful.)
- R_0 would probably be the same in both (Is the number of effective contacts the same in both urban and rural settings? You may find 1.17 Transmissibility: how do we measure infectiousness? useful.)
A: R_0 would probably be higher in an urban area

Q: Assuming that there is a primary case in all households, calculate the household secondary attack rate if there are 244 households with at least one susceptible individual, 827 total susceptible individuals within the households, and 511 of the susceptible individuals become ill.
- 30% (Remember that to calculate the secondary attack rate, you must take the number of susceptible individuals that had contact with an infected individual and became ill and divide that by the total number of susceptible individuals that had contact with an infected individual. You may find 1.17 Transmissibility: how do we measure infectiousness? useful.)
- 48% (Remember that to calculate the secondary attack rate, you must take the number of susceptible individuals that had contact with an infected individual and became ill and divide that by the total number of susceptible individuals that had contact with an infected individual. You may find 1.17 Transmissibility: how do we measure infectiousness? useful.)
- 62% (511 ill / 827 susceptible = 0.62 = 62%)
A: 62%

Q: [Image]

Image: Borchert, et al.

In an Ebola outbreak in Uganda in 2000, a health worker travelled back to her home in Masindi district. 18 members of her extended family became ill over several generations of transmission. Following the primary case, there were 2 secondary cases, 4 tertiary cases, 10 cases in the 4th generation, and 2 in the 5th.

What is the approximate value for R0 in the early stages of this outbreak?
- 2 (From one generation to the next there is an approximate doubling in cases numbers, so R_0 is approximately 2. In the last generation there were probably few susceptible individuals left among the index family)
- 17 (To calculate this, compare the numbers arising in each generation with the previous generation. You may find 1.17 Transmissibility: how do we measure infectiousness? useful.)
- 3 (To calculate this, compare the numbers arising in each generation with the previous generation. You may find 1.17 Transmissibility: how do we measure infectiousness? useful.)
- 6 (To calculate this, compare the numbers arising in each generation with the previous generation. You may find 1.17 Transmissibility: how do we measure infectiousness? useful.)
A: 2