chapter 14 disease and epidemiology MICRO

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pathology
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the study of disease
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etiology
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the cause of a disease
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pathogenesis
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the development of disease (how one gets infected)
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infection
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invasion or colonization of pathogens in the body
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disease
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an abnormal state in which the body is not performing normal functions
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transient microbiota
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may be present for days, weeks, or months and do not cause disease
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normal microbiota
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permanently colonize the host and do not cause disease under normal conditions
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Human Mircrobiome Project
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a project to characterize the microbial communities found on the human body -goal: to determine the relationship between the human micro biome and human diseases
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factors that determine distribution and composition of normal microbiota
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1. nutrients 2. physical and chemical factors 3. host defenses 4. mechanical factors
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microbial antagonism (competitive exclusion)
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a competition between microbes; growth of some microbes prevents the growth of other microbes
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In what ways do normal microbiota protect the host?:
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1. compete for nutrients 2. produce substances that are harmful to invading microbes 3. affect the pH and available oxygen
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symbiosis
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the living together of two different organisms or populations
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commensalism
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one organism benefits and the other is unaffected (symbiosis)
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mutualism
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both organisms benefit (symbiosis)
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parasitism
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one organism benefits and one is harmed without any benefit (symbiosis)
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opportunistic pathogens
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not normally causing disease but can become pathogenic under certain circumstances
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Koch’s Postulates
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criteria used to determine the causative agents of infectious diseases 1. same pathogen must be present in every case of the disease 2. the pathogen must be isolated from the diseased host and grown in pure culture 3. the pathogen from the pure culture must cause the disease when it’s inoculated into a health lab animal 4. the pathogen must be isolated from the inoculated animal and must be shown in the original organism
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exceptions to Koch’s postulates
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-some pathogens can cause severe disease conditions -some pathogens can cause disease only in humans -some microbes have never been cultured
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The first step for directly linking a microbe to a specific disease according to Koch’s postulates is to a. compare blood of a sick animal to blood obtained from healthy animal b. inject a sample of blood or other body fluid form a diseased animal into a healthy animal c. culture the blood or other body fluid from a diseased animal using nutrient medium d. obtain a sample of blood or other body fluid from a diseased animal
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d
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symptoms
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changes in the body that the patient feels as a result of disease
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signs
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changes to the body that can be measured or seen as a result of the disease
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syndrome
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a specific group of signs and symptoms that accompany a disease
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communicable disease
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spread from one host to another
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contagious disease
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spread from one host to another rapidly and easily
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noncommunicable disease
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cannot be spread from one host to another
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incidence
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number of people who contract a disease during a particular time period
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prevalence
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number of people who develop a disease at a specified time regardless of when it appeared first (takes old and new into account)
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sporadic disease
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occurs only occasionally
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endemic disease
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occurs constantly and is present in the population (ex. common cold)
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epidemic disease
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acquired by many people in a given area in a short time (ex. influenza)
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pandemic disease
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worldwide epidemic (ex. AIDS)
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acute diseases
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symptoms develop rapidly but the disease lasts only a short time
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chronic diseases
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symptoms develop slowly and last a long time
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subacute disease
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intermediate between acute and chronic (quick symptoms and hang around longer than acute)
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latent disease
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causative agent is inactive for a time but then activates and produces symptoms
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herd immunity
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immunity to disease(s) in most of a population (ex. measles, mumps, and rubella because vaccinated people do not have it so the unvaccinated are also protected)
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local infection
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pathogens are limited to a small area of the body ex. boils
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systemic (generalized) infection
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an infection throughout the body spread by blood or lymph ex. measles
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focal infection
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systemic infection that began as a local infection in one place then traveled by blood or lymphatic vessels
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sepsis
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toxic inflammatory condition arising from the spread of microbes, especially bacteria or their toxins, from a focus of infection (presence of a toxin or pathogen in blood and tissue)
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septicemia
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systemic infection resulting from multiplication of bacteria in the blood (blood poisoning) -accompanied by fever -can cause organ damage
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bacteremia
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where there is bacteria in the blood
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toxemia
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where there are toxins in the blood
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viremia
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where there are viruses in the blood
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primary infection
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an acute infection that causes the initial illness
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secondary infection
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caused by an opportunistic infection after a primary infection weakens the immune system
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subclinical disease
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does not cause any noticeable signs or symptoms (inapparent infection)
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which of the following shows the correct relationship among the epidemiology terms in terms of number of people affected?
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a. prevalence > incidence > mortality
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The stages of a disease
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1. incubation period 2. prodromal period 3. period of illness 4. period of decline 5. period of convalescence
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incubation period
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between initial infection and the first sings and symptoms
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prodromal period
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short period; early, mild symptoms of disease like aches
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period of illness
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the disease is most severe; patient overcomes disease by end of period
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period of decline
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the signs and symptoms subside **patient vulnerable to secondary infections!
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period of convalescence
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the recovery period where body returns to pre-diseased state; recovery has occurred
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reservoirs of infection
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-continual sources of infection -human reservoirs = carriers may have inapparent infections or latent diseases -animal reservoirs = zoonoses are diseases from animal to human -nonliving = microbes can survive in water (feces) & soil (fungi)
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examples of zoonoses
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-rabies -Lyme disease
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direct contact transmission
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requires close association between the infected and susceptible host
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indirect contact transmission
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spreads to a host by an inanimate object called a fomite
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fomite
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a nonliving object that can spread infection
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droplet transmission
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transmission via airborne droplets less that one meter away
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vehicle transmission
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transmission by an inanimate reservoir (affects large # of people) -waterborne = pathogens spread by water contaminated with untreated sewage -airborne = during coughing and sneezing; one meter -foodborne = pathogens spread by incomplete cooking or bad food storage
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vectors
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animals (arthropods: fleas, ticks, and mosquitos) that carry pathogens from one host to another -they can transmit disease by: 1. mechanical transmission 2. biological transmission
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mechanical transmission
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arthropod transmits disease passively by landing on another host when it has pathogens on feet or body parts
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biological transmission
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arthropod becomes infected from biting human then the pathogen reproduces in arthropod and the disease is transmitted by bite or feces
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A nonliving source of an infectious agent that infects a large number of people is called a a. vehicle b. vector c. fomite d. reservoir
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a. vehicle
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Healthcare Associated Infections (HAIs)
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**infection acquired while receiving treatment in a healthcare facility (nosocomial infections) -affect 1 in 25 patients and result in 20k deaths -result from: microbes in hospital, weak status of patient, and chain of transmission in hospital
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compromised host
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an individual whose resistance to infection is impaired by disease, therapy, or burns
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factors that compromise a patient
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(1) broken skin or mucous membranes (2) suppressed immune system

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