Epidemiology Flashcards
Epidemiology
The study of the occurrence, transmission, distribution, and determinants of health and disease in populations
Etiology
The study of the cause of diseases
Reservoirs
The site or natural environment where a pathogen is normally found living and from which infection can occur
Constantly present disease that occurs at a stead low frequency with predictable changes
Endemic Disease (e.g. common cold)
Sudden increase in occurrence of disease above expected levels
Epidemic Disease (e.g. cholera)
Increase in a disease through large populations and across continents
Pandemic Disease (e.g. plague, AIDS)
Types of reservoirs (3)
Inanimate (soil, water, food)
Animate (animals, insects, humans)
Carriers (infected individuals who can transmit pathogen)
Role of John Snow (4)
- “Father” of epidemiology
- Traced cholera outbreak to a water pump in 1850’s
- Studied cholera and developed hypothesis that contaminated water transmitted the pathogen
- Set principles of public health with his investigations and interventions
Climatic Causal Hypothesis for Haitian Cholera
- Vibrio cholerae is an aquatic bacterium that can lie dormant in costal waters for years
- The Haitian earthquake could have disturbed areas of the Artibonite river that it lived in (likely on copepods), which then infected humans who received contaminated water
Human Causal Hypothesis for Haitian Cholera
- Outbreak began in central Haitian mountains
- Untreated sewage from a UN camp contaminated a tributary of the Artibonite River
- Contaminated water ran downstream and infected index case to start epidemic
Nepal Spread Hypothesis of Haitian Cholera
- Cholera is endemic in Nepal
- Genome of Nepal and Haitian Vibrio cholerae strains are nearly indentical
- Traveller carried cholera from Nepal into Haiti to start epidemic
Herd Immunity
- If a significant fraction of a herd is immunized, the potential for greater exposure is limited
- Each individual contacts other individuals
- The more immunity in the herd, the smaller the chance an infected individual contacts a susceptible individual
Infectious Disease Cycle (5)
Pathogen -> Source of Pathogen -> Transmission to Host -> Susceptibility of Host -> Exit from Host
Host Susceptibility Factors
- Pathogen: Obligate (always causes disease) v. Opportunistic (host-microbe interaction determines if disease is cause; e.g. Strep throat)
- Environmental Conditions
- Host Variability
Factors in Host Variability (6)
- Nutrition
- Stress
- Genetic differences
- Immune competence
- Physical damage to tissues
- Behavioral differences (hygiene, sexual activity, drug use, etc.)
