EPIDEMIOLGY AND DISEASE TRANSMISSION PART 1 Flashcards
an infectious microorganism or pathogen: virus, bacterium, parasite, or other microbe.
AGENT
the study of the distribution and determinants of health-related
states or events in specified populations, and the application of
this studyto the control of health problems
EPIDEMIOLOGY
human who can get the disease
HOST
proportion of exposed persons who become
infected
INFECTIVITY
proportion of clinically apparent cases that are severe or fatal
VIRULENCE
proportion of infected individuals who develop clinically apparent disease
PATHOGENICTY
persons who are infectious but have subclinical disease
CARRIERS
what stage state extending from the time of exposure to onset of disease symptoms
Stage of Subclinical Disease
what period was defined as for infectious diseases
Incubation period (Hepatitis A- as long as 7 weeks)
what period was defined as for chronic diseases
Latency period
may be as brief as seconds for hypersensitivity
Latency period
most diagnoses are made during this stage
Stage of Clinical Disease
the persons with incubating disease or inapparent infection
Carriers
extrinsic factors that affect the agent and the opportunity for exposure
Environment
environmental factors include in Physical Factors
geology and climate
environmental factors include in
socioeconomic factors
crowding, sanitation, and the
availability of health services.
Biological factors
insects that transmit the agent
variety of factors intrinsic to the host
- influence an individual’s exposure
- susceptibility
- response to a causative agent
exposure to an organism will result in disease including
organism’s pathogenicity and dose
what carriers transmits the pathogen during the incubation period
Incubatory carrier
what carriers completely recovered from disease but continue to harbor the pathogen indefinitely
Active carriers
what carriers transmit pathogen during
convalescence or recovery period
Convalescent carrier
what carriers carry the pathogen without ever having the disease
Passive carriers
what routes contaminated food and water; consumption of infected animal products
Ingestion
what routes with infected animal or with domestic pet waste
Direct contact
what routes from contaminated hides, fur, feathers
Inhalation
what routes is an insect vector
Injection of the pathogen
Transmission occurs when the agent leaves its reservoir or host through a portal of exit, is conveyed by some mode of transmission,
and enters through an appropriate portal of entry to infect a susceptible host.
Chain of Infection
Many of these diseases are transmitted from animal to animal, with humans as incidental hosts.
Animal Reservoir
Diseases that are transmitted from person to person without intermediaries
Human Reservoir
an infectious disease that is transmissible under natural conditions from vertebrate animals to humans.
Zoonois
e.g. air, soil, food, milk, water, and fomites
Inanimate Reservoir (non-living)
e.g. air, soil, food, milk, water, and fomites
Inanimate Reservoir (non-living)
contaminated by dust, smoke, and respiratory secretions of humans expelled into the air by breathing, blowing, sneezing, and coughing
Air
contaminated materials
Fomites
Inanimate Reservoir - e.g. clothing, bedding, urinals/bedpans, eating and drinking utensils
Fomites
the path by which a pathogen leaves its host and usually corresponds to the site where the pathogen is localized
Portal of Exit
[Portal Of Exit]
Influenza and Mycobacterium tuberculosis
respiratory tract
[Portal Of Exit]
Influenza and Mycobacterium tuberculosis
respiratory tract
[Portal of Exit]
Schistosomes
urine
[Portal of Exit]
Cholera vibrios
feces
agents can exit by crossing the placenta
from mother to fetus (rubella, syphilis, toxoplasmosis),
Some bloodborne
others exit through cuts or needles in the skin
Hepatitis B or Malaria
how an infectious agent can be transferred
Mode of Transmission
occurs through skin-to-skin contact, kissing, and sexual intercourse
Direct transmission
spread by direct contact with contaminated
soil
hookworm
other infectious are spread from person to person by direct contact
mononucleosis (“kissing disease”) and gonorrhea
spray with relatively large, short-range
aerosols produced by sneezing, coughing, or even talking
Droplet Spread
transmitted from patient to a susceptible host by droplet spread
Pertussis and meningococcal infection
Long recognized zoonotic diseases include:
- brucellosis (cows and pigs)
- anthrax (sheep)
- plague (rodents)
- trichinellosis/trichinosis (swine)
- tularemia (rabbits)
- rabies (bats, raccoons, dogs, and other mammals)
Disease transmitted from person to person includes sexually transmitted diseases, measles, mumps, streptococcal infection, and many respiratory pathogens
Human Reservoir
