Lecture 20 Epidemiology Flashcards
A. What is epidemiology?
Study of when and where diseases occur and how they are transmitted
- What is the difference between communicable and non-communicable disease? Examples
Communicable disease: An infectious disease that can be transmitted from one host to another N.C- heart disease
B. Rate of disease in a population
Proportion of a given population infected with a disease (often reported per 100;000)
a. Why are epidemiologist more concerned with the rate of disease rather than the absolute number of cases?
Because the rate is based on % which is a more effective comparison
Morbidity rate
(# of sick people)/(size of population)
Mortality rate
% of population that dies from a disease
Incidence
of new cases of a disease in a given time period
Prevalence
The total # of cases of a given disease (old and New)
Define endemic and Example
A disease of other occurrence that is constantly present I a population (polio)
Define epidemic and Example
A disease or other occurrence that has much higher incidence than usual (Ebola)
Define pandemic and Example
Epidemic that crosses over the world HIV
What are the links in the chain? 6
1) Causative agent 2) reservoir 3) Portal of exit 4) Mode of transmission 5) portal of entry 6) susceptible Host
Virulence factors of an agent
Molecules that allow a pathogen to overcome the body’s defenses and cause disease
Infectious dose of an agent
Infectious dose: number of pathogens required to cause disease in the host
Incubation period of an agent
Incubation period: time between exposure to a pathogen and appearance of signs/symptoms
- Reservoirs of infection
Can be from Human(symptomatic or Asymptomatic) Animals and Environment
i. Symptomatic infections
Show sign and symptoms
ii. Asymptomatic carriers
No signs or symptoms
- Portals of exit
How the pathogen leaves a host Examples: Diaheara/vomiting; Droplet transmission
horizontal v. vertical transmission
Vertical is from a mother and horizontal is between people
Direct v. indirect Contact
Direct (touching/Droplets) indirect involves an inanimate surfaces (used needles)
mechanical v. biological Vectors
Mechanical - only transfer of pathogen(ticks) Biological - Vecto is part of pathogen life cycle (malira)
Portals of entry name 5
Where a pathogen enters the host orfuses like eyes ears respiratory track; digestive track; broken skin ; urinary track; genital track
Host-Predisposing factors:
Epidemiology(health risks like; Immunity to pathogen; General Health; Age; Gender; religious cultural; genetic background