Lecture 7: Control of Infectious disease Flashcards
Why is the iceberg concept important?
Because people who are asymptomatic can also spread the disease
Who is a carrier of a disease?
A carrier is an individual who harbors the organism but is not shown as being infected through testing or shows no evidence of clinical illness. This person can still infect others, although the infectivity is generally lower than with other infections.
The Potential of an infectious agent to spread depends on what 4 factors?
1- Probability of transmission in a contact between an infected individual and a susceptible one
2- Frequency of contacts in the population -
contact patterns in a society
3- Duration of infectiousness
4- Proportion of the population/contacts that are already immune, not susceptible
What is Basic Reproductive Rate (R0)?
Average number of individuals directly infected by an infectious case (secondary cases) during his or her entire infectious period, when she or he enters a totally susceptible population
What does it mean that R0 <1?
The disease will disappear
What does it mean that R0=1 ?
The disease will become endemic
What does it mean that R0 >1 ?
There will be an epidemic
What is R0 affected by?
The frequency of contacts in the host population
The probability of infection being transmitted during
contact
The duration of infectiousness
What is the formula for Ro, the basic reproductive rate?
Basic formula for the actual value: R0 = β * κ * D
- β - risk of transmission per contact (i.e. attack rate)
- κ - average number of contacts per time unit
- D - duration of infectiousness measured by the same
What is R?
Effective Reproductive Number
What happens at the initial phase?
R=R0
What happens at the Peak of epidemic?
R=1
What is immunisation?
Is primary prevention
Immunization is the process whereby a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine. Vaccines stimulate the body’s own immune system to protect the person against subsequent infection or disease.
What is Herd Immunity?
Level of immunity in a population which prevents epidemics even if some transmission may still occur
Presence of immune individuals protects those who are not themselves immune
What is the the Herd Immunity Threshold?
Minimum proportion (p) of population that needs to be immunized in order to obtain herd immunity
