Epidemiology Flashcards
Describe the 4 modes of transmission
- Airborne: (i) droplet (1-4um travel ≥1m); 9ii) dust particles
- Contact: (i) Direct; (ii) indirect (fomite); (iii) droplet (>5um travel <1m)
- Vehicle: contaminated e.g. food/H2O, fomite
- Vector-borne: (i) External/mechanical transmission (no growth in vector) e.g. flies; (ii) Internal/biolagical transm. (grows in vector) e.g. malaria in mosquitoes
What’s the difference between the types of epidemic: common source & propagated epidemics
- Common source: sudden increase of infection - disappears w/in a couple of days e.g. food poisoning
- Propagated: takes time for no. of infection to increase (bell-shaped bc after a while ppl become immune to it) e.g. strep throat
Define herd immunity.
large %age of population immune to a disease to resist the spread of infection
How can the levels of herd immunity be altered?
- introduction of new susceptible individuals to population
2. Antigenic drift or shift => changes to pathogen
What’s the difference b/w source & reservoir of pathogen
- Reservoir: natural(/initial) location pathogen is normally found
- Source: the common location the pathogen is transmitted e.g. fomite like door handles OR carriers
3 types of measures that can be used to control an epidemic
- Reduce/eliminate the source/reservoir of infection: eg quarantine carriers/infected OR destroy animal reservoir
- Break the connection b/w source & individual: pasteurisation of milk OR chlorination of water
- Reduce no. of susceptible individuals: raise herd immunity via passive/active immunity
How can the frequency of disease be measured (3)?
- Morbidity rate: aka incidence = # new cases / #popu.
- Prevalence rate: total # of cases
- Mortality rate: # deaths bc disease / # disease- infected ppl
How might a high host morbidity be advantageous for a pathogen as opposed to a high host mortality?
High host morbidity may be advantageous because the pathogen can live in the host as long as possible as it has access to nutrients (while the host is still alive)= survive longer
*What’s a nosocomial infection and what is a major source for pathogens involved?
Infection acquired from staying in hospital (NF->opportunistic pathogen).
Source: artificial surfaces, air conditioning, cleaners, bed making, ventilation ducts
What are the reasons for the emergence of new infections?
- Increased mobility
- overuse of drugs
- climate change
- changes to environment e.g. habitats lost
- poor sanitation
Differentiate b/w endemic, epidemic, outbreak & pandemic
- Endemic: a low-freq. of infections in a pop. @ a regular interval
- Epidemic: Sudden spike in freq. above expected no.
- Outbreak: Sudden occurrence of disease for a certain group in a pop. e.g. 4yr olds
- Pandemic: disease present worldwide
What are the types of carriers? (4)
- Active: clinical case of disease (show signs & symptoms)
- Convalescent: recovering from disease but still contagious
- Healthy: asymptomatic (not ill)
- Incubatory: has pathogen but not YET ill (incubation period)
List the symptoms you would get during the stages of infection
- incubation period: no symptoms since initial exposure
- Prodomal phase: Mild, non-specific symptoms (contagious)
- Illness: severe, characteristic signs & symptoms
- Convalescence: recovery period, S&S reduced
List the components in the chain of infection
- pathogen: tests in lab-> ID
- source of pathogen: source/reservoir
- transmission to host
- susceptibility of host: i) immunity of host. ii) pathogenicity of pathogen
- Exit from host: active vs passive (excreted out of body)
