Epidemiology Flashcards
Epidemiology
The study of occurrence, spread and control of disease
What do epidemiologists study?
The factors that determine the frequency, distribution and causes of human disease mainly concerned with determining ways to prevent, control and eradicate diseases in the population
Factors that determine the frequency, distribution and causes of human disease
Characteristics of the pathogen
Susceptibility of the population
Reservoirs of the pathogens
Means of transmission
Communicable disease
An infectious disease that can transmitted from one person to another
Contagious disease
An infectious disease that is easily transmitted from one person to another
Zoonotic disease
An infectious disease that humans can catch from animals
carriers include birds (bird flu), Rodents (the plaque), Mosquitoes (Malaria)
Incidence
The number of new cases of a particular disease within a certain population (suburb, town) during a specific period of time
Morbidity rate
The number of new cases of a disease over a defined period of time in a specifically defined number of individuals
Mortality rate
The ratio of the number of people who died of a particular disease over a specified time period in a specific region
Sporadic Disease
A disease that occurs only occasionally within a population of a specific geographical area
Epidemic
A disease that is occurring in greater than usual numbers within a specific geographical region
Usually only lasts a short period of time
Endemic
A disease that is always present at some level within a population of a specific geographical area
Pandemic
A disease that is occurring in epidemic proportions in many countries at the same time
Occasionally worldwide e.g Bubonic plague, Spanish influenza, AIDS
Chain of infection
Infectious agent Reservoir Portal of exit Mode of transmission Portal of entry Susceptible host
Infectious agent
The pathogen that causes the disease
Reservoir
Places in the environment where the pathogen lives
Including people, animals, formites, soil and water
Portal of exit
The way the infectious agent leaves the reservoir
Through open wounds. aerosols, splatter of body fluids (sneezing and coughing)
Mode of transmission
The way the infectious agent can be passed on
Through direct or indirect contact, inhalation, ingestion
Portal of entry
The way the infectious agent can enter a new host
Through broken skin, catheters, respiratory tract….
Susceptible host
Can be any person
Vulnerability is increased in patients who are immunocompromised, receiving chemotherapy and have catheters
Human Reservoirs - Carrier
A person infected with a particular pathogen, but where the pathogen is not currently causing disease in that person
Pathogen can be transmitted from the carrier to other individuals
Human Reservoirs - Passive carrier
A person who carries a disease causing pathogen without having ever had the disease
Human Reservoirs - Convalescent carrier
A person who can transmit a particular pathogen while recovering from an infectious disease
Human Reservoirs - Active carrier
A person who has completely recovered from a particular disease but still continues to harbour the disease causing pathogen indefinitely
Participial modes of transmission of infectious diseases
Contact (direct or indirect)
Droplets
Airborne
Vehicular (contaminated inanimate objects)
Vectors (various biting or injecting animals)
Common ways communicable diseases are transmitted
Direct: skin-skin contact mucous membrane-mucous membrane contact Indirect: Airborne droplets Food or water contaminated with faecal material Arthropod vectors Contaminated fomites Contaminated blood or blood products by parenteral injections
Health care associated infections (HAIs)
Infections that are acquired within hospitals or other healthcare facilities
Usually within 48 hours of admission
Examples of Health care associated infections (HAIs)
Surgical site infections (SSI)
Central line-associated bloodstream infections (CLABSI)
Catheter Associated UTIs
Community acquired Infections
Infections that are acquired outside of a health care facility
