Calculating the Reproductive Ratio

1
Calculating the Reproductive Ratio

• Counter Plague

2
Reproductive Ratio, R0

• The average number of new infections we expect to
  see for each infected person in the epidemic.
• For Standing Disease, R0 is 2

Step 0 1 2 3 4 5 6 7
No. new infections 1 2 4 8 16 32 64 128
3
Counter Plague1st scenario
No. on die No. of new infections
1 0
2 0
3 1
4 1
5 2
6 3

• What is the average number of new infections we
  expect to see for each infected person?
• Use the probability of each outcome to calculate
  R0 for this scenario.

4
Counter Plague1st scenario
No. on die No. of new infections Av. no. new infections expected
1 0 0
2 0 0
3 1
4 1
5 2
6 3

• What is the average number of new infections we
  expect to see for each infected person?
• Use the probability of each outcome to calculate
  R0 for this scenario.
• R0

5
Counter Plague2nd scenario
No. on die No. of new infections
1 0
2 0
3 1
4 1
5 1
6 2

• What is the average number of new infections we
  expect to see for each infected person?
• Use the probability of each outcome to calculate
  R0 for this scenario.

6
Counter Plague2nd scenario
No. on die No. of new infections Av. no. new infections expected
1 0 0
2 0 0
3 1
4 1
5 1
6 2

• What is the average number of new infections we
  expect to see for each infected person?
• Use the probability of each outcome to calculate
  R0 for this scenario.
• R0

7
Counter Plague
No. on die No. of new infections Av. no. new infections expected
1 ? ?
2 ? ?
3 ? ?
4 ? ?
5 ? ?
6 ? ?

• How could you set up Counter Plague so that R0
  equals
• 1.5
• 4
• What is the largest value of R0 you can get in
  Counter Plague?