05 Infectious disease Epidemiology

Question 1

Name the three case orders

Answer 1

1. Index case: first case discovered by the health care system
2. primary case: first case in the population
3. secondary case: later cases

Question 2

Name the time periods

Answer 2

• latent period: time between infection and start of infectious phase
• infectious period: time where patient can infect others
• incubation period: time between infection and disease, can be dose-dependent
• serial interval: time between appearance of similar symptoms in successive generations
• generation time: time from infection of primary case until time of infection in secondary case

Question 3

What is the R-number?

Answer 3

• reproductive rate R
• R0 is basic reproductive rate

takes into account:
- probability of transmission (ß)
- frequency of contacts (k)
- duration of infectious period per person (D)

( - proportion of susceptible population (P) )

Question 4

Calculate the threshold for herd immunity

Answer 4

1 - 1/R0

ex. Measles: R0 = 15
-> 1 - 1/15 = 14/15 = 0.94 = 94%