attack rate: the % of people who get sick after exposing to something
relative risk: the % who become ill in one group divided by the % who become ill in another group, i.e. the ratio of two attack rates
case & control 实验组与对照组？
incidence & prevalence: Thinking about a tank of prevalent cases, then the incident cases shoud come in while dealth or recovery should come out.
prevalence: number with the disease/population size
prevalence depends on incidence rate and duration:
incidence: number of new cases/population size at risk
case-fatality ratio(CFR): the percent of people with the condition who die in a time period (death/cases)
age-adjusted death rate:
Sometimes there is no midpoint and we will use the upper bound of each age group.
disability-adjusted life year(DALY): the day you could live times your life quality (from 0 to 1)
When there will be multi-possible outcomes, use:
potential years of life lost(PYLL):
R0 - the number of people that one person could spread to
We could reduce R0 by:
- vaccinating and reduce the number of people who are susceptible
- quaranting, to reduce transmission (or culling animals)
- Recovered or removed
S + I + R = 1
Given transmission rate and recovery rate :
Or, you have to add births, deaths, migration or carriers of a disease.
After adding death parameter =birth parameter , where is the death possibility of the disease:
To stop an epidemic, we need R0<1.
- make S small by vaccinating
- make small by washing hands or social distancing
- make large by quarantine(shorten)
herd immunity: we only need to vaccinate a portion of people to eradicate an infection, the portion is:
incubation period: the time between infection and onset of clinical disease/symptoms
latent period: time between infection and becoming infectious