Epidemiology

epidemiology

• the science that underlies public health

  • studies how disease originates and spreads throughout a populations, with the goal of preventing outbreaks and containing them when they do occur

  • specifically looks at distribution of disease and risk factors for disease and applying knowledge to preventing outbreaks

endemic

regularly occurring in an area

sporadic

occurs infrequently and irregularly

epidemic

contagious illness that spreads quickly and affects more people than expected in a specific area or community

pandemic

when a new disease or new strain of an existing disease spreads worldwide

prevalence

• # existing cases of disease in a population during a defined period of time

• individuals with outcome of interest regardless of when diagnosed

• how much a population is affecgted

incidence

• # new cases of disease that develop in a population during a defined period of time

• individuals who change in disease status over a specified period of time

• how quickly are people becoming infected

case fatality rate

• mortality rate/incidence rate

• indicates how virulent a disease is

infectious diseases

• may/may not be communicable

  • ex. food poisoning, tetanus

communicable disease

an infectious disease that is contagious and which can be transmitted from one infected host to another

reproductive number (R0)

measure of contagiousness

incubation period

time after initial exposure to microbe

promodal period

nonspecific generalized symptoms

period of illness

specific signs and symptoms

period of decline

gradual lessening of symptoms

period of convalescence

return to normal health after disease

periods where a host is contagious

all periods of illness

resevior

• where microorganisms can live, accumulate or persist outside of the host of interest

  • serves as a source of infection for other host organisms

  • ex. humans, animals, non-living (water, soil)

carriers

• passive or active

• asymptomatic or symptomatic

zoonotic pathogens

• infections that normally afflict animals but can be transmitted to humans

• acquired through various routes

• cause of most new emerging infectious diseases (75%)

definitive host

preferred host

• if animals are preferred and infect humans, humans are usually dead-end and do not infect other humans

direct transmission

• skin-skin

• mucous-mucous (STIs)

• vertical: via placenta or breast milk

indirect transmission

• droplets: close range (1m)

  • fomites

fomites

inanimate objects that transmit pathogens (ex. doorknobs)

air-borne transmission

• aerosols

  • droplet nuclei inhaled (long distance)

vehicle transmissions

• water borne

• food borne

vector transmission

• living organisms that can carry pathogens

• arthropods: insects and arachnids

nosocomial disease

infection that occurs while a patient is in a healthcare facility

notifiable disease

a disease that is legally required to be reported to government authorities when diagnosed

chain of infection

• infectious agents

• reservoirs

• portals of exit

• modes of transmission

• portals of entry

• susceptible host

interruption of infectious agents

antimicrobial drugs

interruption of reservoirs

social distancing/avoid contact with reservoir

interruption of portals of exit

wearing a mask

interruption of modes of transmission

hand washing

interruption of portals of entry

wearing a mask

interruption of susceptible host

vaccination