Epidemiology Flashcards
1
Q
What is epidemiology
A
- Study of the distribution and patterns of health events
- Health characteristics and their causes or influences in well defined populations
- Cornerstone method of public health research and practice
- Critical to understand how to treat and prevent diseases
- Diseases are described in terms of prevalence, incidence, virulence or relative pathogenicity
2
Q
How do we control disease
A
- Rely on surveillance, observation, recognition and reporting of diseases as they occur
- Ability to trace spread of disease to identify its origin and mode of transmission
3
Q
What is incidence vs prevalence of disease
A
- Incidence: Number of new cases of the disease in a given period of time
- Prevalence: Total number of new and existing cases in a population in a given time
4
Q
What is the difference between sporadic, endemic, epidemic and pandemic
A
- Sporadic: Random outbreak of a limited number of cases of infection within a defined area / region
- Endemic: Disease is constantly present in a population, usually at low incidences, infected individuals causing disease are reservoirs (human / non)
- Epidemic: Disease occurs in a large number of people in a population at same time
- Pandemic: Larger number of cases that are widespread within a country, but cases are observed worldwide
5
Q
What are the different stages of infection
A
- Infection: Organism invades and colonises the host
- Incubation Period: Time between infection and onset of symptoms
- Acute Period: Disease is at its height
- Decline Period: Disease symptoms are subsiding
- Convalescent Period: Patient regains strength and returns to normal
6
Q
What is mortality vs morbidity and DALY
A
- Mortality: Incidence of death in a population
- Morbidity: Incidence of disease, including fatal and nonfatal diseases in a population
- DALY: Quantitatively measures disease burden in terms of lost years due to disease, disability due to disease and premature death
7
Q
What is coevolution of the host and pathogen
A
- Virulence of parasite in host to host transmission diminishes, resistance of host increases
- Pathogen that kills its host before it can infect another host may become extinct
- If a pathogen does not rely on host to host transmission it may remain extremely virulent (E.coli)
8
Q
What is direct vs indirect transmission
A
- Direct: Infected individual transmits a disease directly to a susceptible host without assistance of an intermediary, examples include flu, common cold, STI’s and ringworm
- Indirect: Occurs when transmission is facilitated by a living (vector) or nonliving agent (fomite)
9
Q
What is zoonosis
A
- Any disease that primarily infects animals but is occasionally transmitted to humans
- Transmission occurs through vectors, air / food borne, close proximity to nature, direct contact
- Control of a zoonotic disease in the human population may not eliminate disease as a potential public health problem
- Some have complex life cycles involving an obligate transfer from a nonhuman host to humans followed by transfer back to the nonhuman host (malaria)
10
Q
What is a carrier of disease
A
- Pathogen-infected individuals showing no signs of clinical disease
- Potential sources of infections
- May be individuals in incubation period of disease
- Can be identified using diagnostic techniques, including culture and immunoassays
- Typhoid Mary (cook who infected 50 individuals)
11
Q
What are the different ways that carriers can be classified
A
- Type: Incubatory (short time, asymptomatic), convalescent (recovering, no sterilising immunity, carry infectious pathogens), healthy (asymptomatic with infectious pathogen)
- Duration: Temporary or permanent
- Portal of Exit: Released via a specific exist depending on the location of infection (urinary, intestinal, respiratory)
12
Q
What are the key methods for control and spread of disease
A
- Against Vehicles: Food laws, water purification
- Against Reservoirs: Animals (immunised / destroyed), humans (quarantine, immunised, treated)
- Against Transmission: Immunisation, quarantine, surveillance, contact tracing
13
Q
What is R0
A
- Number of expected secondary cases of a given disease from each single case
- Mathematical model assumes an entirely susceptible population
- Different diseases have different R0
- Estimate of how many people will be infected by an average individual with the disease
14
Q
Why is R0 important in epidemiological studies
A
- Epidemiological studies involve a systemic approach
- Attempt to describe “what, who, where, when, and why/how” of a situation
- Counts cases or health events, and describes them in terms of time, place, and person
- Divides the number of cases by an appropriate denominator to calculate rates
- Compares these rates over time or for different groups of people
- Involves a case definition (confirmed, probable, suspected)
15
Q
What is descriptive epidemiology
A
- Identifying information
- Demographic information (characterise population at risk)
- Clinical information (epidemic curve created, spectrum of illness)
- Risk factor information (tailored)
- Extent and pattern of public health problem being investigated
- Detailed description of the health of a population that can be easily communicated
- Identify areas or groups within the population that have high rates of disease
- Provides important clues to causes of disease, and thus a testable hypotheses
