Disease Transmission Flashcards
Attack rate
Attack rate =
AtRiskThatBecameILL / (AtRiskIndividuals+ HealthyIndividuals)
x 100
or SICK(SICK+WELL)
Not a true rate. Doesnt specify time. Proportion of who ate a food.
Good for outbreak or infectious disease like enteritis..
Similar to Cumulative incidence where:
CI = NEW CASES / POPULATION AT RISK
Endemic
Presence of a disease or infectious agent within a given geographic area or a population without importation from outside (usual occurrence)
Malaria in Africa
Sporadic endemic: Occasional cases ocurring at irregular intervals
Hyper-endemic: Highly level of occurrence in an endemic area.
Epidemic
An outbreak or epidemic is when there is a sudden increase in cases of a particular disease than what is expected in a given area or among a specific group in a particular time.
Seasonal flu
A sudden increase in cases in one area from what is normally expected in a population
Pandemic
Epidemic affecting a large proportion of the population. It is a worldwide epidemic.
COVID-19, Spanish flu 1918
Herd immunity
Resistance of a group of people to an attack by a disease to which a large proportion of the group members are immune
Cornerstone of vaccination. Smallpox was erradicated by this method.
When large proportion is immune, entire populaiton likely to be protected not only immune.
is just achieveing immunity in a population and can be either trough vaccination or previous infections. prevent outbreaks and protect the entire population
The protection on Herd immunity depends on
- Extent of random mixing of population
- Agent and transmission characteristics
- Environmental factors
- Number of susceptibles and immunes
The level of protection in Herd immunity can be altered by
- Introduction of new susceptible individuals to the population
- Change the infecting agent
2.1 Antigenic shift (major changes, character of pathogen, recombination in birds into new antigen types)
2.2 Antigenic drift (small changes due point mutation)
