Basic Reproduction Number, R0

Basic reproduction number R0
R0 tells you the average number of people who will catch a disease from one contagious person.

Spread into a population with no previous exposure to the antigen

Assumes no pre-existing immunity through exposure or vaccination

R0 = 1
R0 greater than 1
R0 less than 1

Determining factors of R0

Infectious period
How long an infection is contagious for
Flu, typically up to 8 days
Flu in children, up to two weeks
Longer an infection is contagious for, the higher the R0

Contact rate
How many people an infected person comes into contact with
E.g. R0 will be lower if a person stays at home, higher if they are out and about

Mode of transmission
Shedding pottential
Rapid speed if airborne, flu or measles. No physical contact or fomite necessary
Slower if transmitted by body fluids, e.g. Ebola, Hepatitis B, C, or HIV,

Influenza Droplet R0 = 0.9 – 2.1
2009 Droplet R0 = 1.4 – 1.6
Hepatitis C Body fluids R0 = 2
Ebola Body fluids R0 = 2
1918 Droplet R0 = 1.4 – 2.8
HIV Body fluids R0 = 4
Smallpox Droplet R0 = 3.5 - 6
Mumps Droplet R0 = 4-7
Pertussis Droplet R0 = 5.5
Measles Airborne R0 = 18

Super-spreaders
20/80 rule
20% of infected individuals are responsible for 80% of transmissions

Individual reproductive number