SLCC Pathophysiology - Unit 4
Infectious Disease and Epidemiology
*Prions* - answer Protein molecule - mutated form causes brain disease in humans &
animals -i.e. mad cow disease. Can incubate for decades before s/s appear. S/S of
brain damage. No cure currently.
*Virus* - answerRequires a host cell -often bacteria- to inject it's "viron" particle into the
host cell which then triggers the host cell's DNA or RNA to replicate a virus. *Needs a
HOST to replicate & survive*
*Bacteria* - answerSingle cell organisms classified as either- *Gram Positive* or *Gram
Negative*
*Reproduces independently - does NOT need a host*
Bacteria
Gram Positive - answerExotoxin producing- releases a toxin while alive and
reproducing.
Bacteria
Gram Negative - answerEndotoxin producing- does not release it toxin until bacteria
dies -as it does when a person is on antibiotic medication-. High levels of endotoxin can
trigger *septic shock, DIC, & ARDS*
*Chlamydia & Rickettsia* - answer*Reproduce independently like bacteria, but need a
host cell for energy, like viruses*
Chlamydia - answerIs a sexually transmitted disease
Rickettsia - answer-carried by ticks and live- causes Rocky Mountain Spotted Fever.
*Fungal Pathogens* - answerTransmitted by spores -molds & yeast-. The cause of
many *"opportunistic" infections* in an immunocompromised host.
Fungal Pathogens
Examples - answerPeople with AIDS or on chemotherapy are prone to get oral "thrush"
& other yeast or fungal infections. Women taking antibiotics can develop a vaginal
overgrowth of candida albicans. See page *304* of text for *an explanation how this
occurs.*
, *Protozoal Pathogens* - answerProtozoa are parasitic animals that infect or colonize
other animals, which then transmit them to humans. In some cases, the directly
infection the human host. Parasites can be transmitted by food/water, feces, or insects -
worms or ticks/fleas/lice-.
*Incubation* - answer*NO S/S*. The number of pathogens in the body have NOT
reached a large enough number to cause symptoms.
*Prodrome or Prodromal* - answer*First onset* of signs and symptoms of an infection.
*Acute* - answerPhase of maximum effect -damage- to the body. Can be further
delineated by the "Invasive" & "Decline" phase of Acute Infection.
*Resolution or Convalescence* - answerThe body's defences begin to overcome the
pathogen and signs and symptoms decrease.
*SIGN* - answer*Objective* information regarding an illness. Can *be
seen/felt/heard/smelled* by another person and/or "measured". Examples: temperature,
weight, the condition of a wound, the character of the pulse, breathsounds heard
through a stethoscope, etc.
*Symptom* - answer*Subjective* information regarding an illness. Cannot be
seen/felt/heard/smelled by another person, or measured with objectives instruments.
Pain is always a subjective finding because the patient is the only one to experience it.
Epidemiology - answerThe study of health in populations to understand the causes and
patterns of health and illness. The scientific method used by "disease detectives" -
epidemiologists- to get to the root of a public health problem or emerging public health
event affecting a specific population.
Chain of Infection - answerThe traditional epidemiologic triad model holds that infectious
diseases result from the interaction of agent, host, & environment. More specifically,
transmission occurs when the agent leaves its *reservoir* or Host through a *portal of
exit*, is conveyed by some *mode of transmission*, & enters through an appropriate
*portal of entry* to infect a *susceptible host*
Portal of Entry - answerThe routes by which an infectious agent can infect a susceptible
animal. One route is usually primary, such as oral for salmonella, but agents can often
enter by other secondary routes, such as conjunctival or rectal -iatrogenic transmission-
for salmonella.
Portal of Exit - answerThe routes by which an infectious agent exits its host, such as
feces, urine, saliva, expired air, blood, semen or urogenital secretions. One route is
usually primary, such as fecal for enteric infections, but the agent may also exit by
secondary routes, such as blood, saliva, or urine during septicemia.
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