epidemiology
study of patterns, causes, and effects of disease at the population level
etiology
study of causation
theories of causation (2)
- miasma theory
- germ theory
miasma theory (2)
- disease caused by bad air originating from decaying organic matter
- not believed to be contagious
germ theory (3)
- disease caused by microorganisms
- transmitted by air, water, contact
- fomites were contaminated surfaces
R0 formula
rate of transmission in humans / (lethality + rate of recovery + death from other causes)
dead-end host
host that dies or recovers before passing the disease on
incubation period
time between infection and starting to show symptoms
latency period
time between infection and becoming contagious
BSL (4)
BSL-1: well-known pathogens that are typically not disease causing
BSL-2: moderate risk but preventative measures are known (vaccines)
BSL-3: high risk due to airborne transmission and causes severe illness. may or may not have vaccines
BSL-4: extreme risk due to easy transmission, severe illness, and often exotic
Methods of transmission (6)
- airborne
- waterborne
- bloodborne
- vertical
- sexual
- contact
virgin field
population with no immunity against a specific disease
herd immunity
when a large enough percentage of a population is immune that those without immunity are still protected
types of vaccines (7)
- killed
- attenuated
- toxoid
- subunit
- conjugate
- recombinate
- mrna / dna
valence
how many pathogens a vaccine protects again
vaccines may also contain… (6)
- medium to grow the pathogen
- nutrients for pathogen
- preservatives / antibiotics to prevent other growth
- formaldehyde to deactivate pathogen
- adjuvants
- stabilisers
thimerosol
preservative wrongly accused of causing autism
zoonotic disease
diseases transmissible from animals to humans
reservoir host
pathogen’s natural host used for its primary means of survival
spillover event
when a pathogen jumps between species
conditions to be considered an emerging disease (4)
- previously unknown
- new location or population
- known but new epidemiological condition
- re-emerging after long periods
influenza types (3)
A: zoonotic, most likely to cause epidemics
B: only infects humans
C: very mild
factors affecting transmission (6)
- pathogen’s characteristics
- population density
- international travel/trade
- water quality
- climate
- healthcare quality
