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Chapter 8
SIR Models
So=9998 Io=2
Ro=0
duration of Infection= 2 days
Recoveries=(Infected Population)/(duration of infection)
Can use summer for Affected population
Recoveries per day
=Infected population / infection duration
Infectivity (rate)=0.25 per contact
Contacts per day=6 per infected person
Total contact per day=6 * Infected Population
Sensitivity Analysis
• Contact number
= (infectivity) (contacts per day) (infection duration)
Sometimes referred to at Ro the reproductivity number
(The number of new infections) / (a single infected person)
R>1  epedemic R<1 disease dies out
Sensitivity run Infectivity=1-50% 2-25% 3-12.5%
Sensitivity run Infection duration = 1-4 days
2-2 days 3-1 day
Policy analysis
• What can we do??
1918 influenza pandemic
50 to 100 million died worldwide
1918 Influenza: the Mother of All Pandemics
Jeffery K. Taubenberger* and David M. Morens
Emerging Infectious Diseases • www.cdc.gov/eid
Vol. 12, No. 1, January 2006