Chapter 14 - Principles of Disease and Epidemiology Flashcards
Pathology
-the scientific study of disease
Etiology
-the cause of the disease
Infection
-the invasion or colonization of the body by microorganisms
Pathogenesis
-the manner in which the disease develops
Disease
-occurs when an infection results in any change from a state of health
-abnormal state where normal functions don’t perform
In Utero
before birth
Absence of Symptoms
-infections can occur in the absence of symptoms
Microbiomes
-microbial communities
-live in and on the human body
Normal Microbiota
-colonize but don’t produce disease under normal conditions
Transient Microbiota
-present for several days, weeks, or months then disappear
Factors that Affect Normal Microbiota
-age
-nutrition
-diet
-health status
-disability
-hospitalization
-stress
-climate
-geography
-living conditions
-occupation
-lifestyles
Normal Microbiota: SKIN
-propionibacterium
-staphylococcus
-corynebacterium
-micrococcus
-acinetobacter
-fungi
Skin
-secretions in sweat and oil glands have antimicrobial properties
-keratin resistant barrier
-low pH
-low moisture content
Eye
-same microbiota found on skin
-tears and blinking eliminate/inhibit microbes
Nose and Throat (URS)
-microbial antagonism
-nasal secretions and mucus remove microbes
Mouth
-moisture, warmth, food support large populations
-saliva has antimicrobial substances
Large Intestine
-largest numbers of resident microbiota
-mucous has antimicrobial agents
Urinary & Reproductive
-vagina: acid tolerant population
-pH and urine flow remove microorganisms
Microbial Antagonism/Competitive Exclusion
-normal microbiota benefit host by preventing overgrowth of harmful microorganisms
-nutrients, conditions, invasion
Candida albicans
-grow in vagina
-a yeast
-flourish in neutral pH
Symbiosis
-one organism is dependent on the other
-ie. normal microbiota and host
Bacteriocins
-produced in large intestine by E. coli cells
-proteins that inhibit the growth of closely related bacteria
Commensalism
-one organism benefits and the other is unaffected
-ie. S. epidermidis
Mutualism
-both organisms benefit
-ie. E. coli
Parasitism
-one organism benefits at the expense of the other
-ie. Influenza
Opportunistic Pathogens
-when a mutual organism can become harmful
-don’t cause disease in normal habitat but may in a different environment
-ie. E. coli
Koch’s Postulates
-showed how a specific infectious disease (anthrax) is caused by a specific microorganism (B. anthracis)
Koch’s Postulates
- same pathogen must be present in every case
- pathogen must be isolated from host and grown in pure culture
- pathogen must cause disease in a healthy animal
- pathogen must be isolated and shown as the original organism
Exceptions to Koch’s Postulates
-some pathogens can’t be grown on artificial media
-some pathogens cause several disease conditions
-some diseases cause different/similar signs and symptoms
Symptoms
-changes in body function
-evidence of an altered state
-subjective
-ie. pain
Signs
-objective changes
-observable and measurable
-ie. fever
Syndrome
-specific group of signs/symptoms that always accompany a particular disease
Communicable Disease
-a disease where an infectious person transmits an infectious agent
-directly or indirectly
-the other person becomes infected
-ie. chicken pox, herpes
Contagious Diseases
-capable of spreading easily and rapidly
-very communicable
-ie. measles and chicken pox
Noncommunicable Disease
-not spread from one host to another
-caused by microorganisms that normally inhabit the body
-occasionally produce disease
-ie. C. tetani
Incidence
-the number of people in a population who develop a disease during a particular time period
-an indicator of spread
Prevalence
-number of people in a population who develop a disease at a specific time
-accounts for old and new cases
Epidemic Disease
-many people in a given area acquire a disease in a short period
-ie. influenza, AIDS
Endemic Disease
-a disease constantly present in a population
-ie. common cold
Pandemic Disease
-an epidemic that occurs worldwide
-ie. AIDS, Covid-19
Acute Disease
-develops rapidly but lasts only a short time
-ie. influenza
Chronic Disease
-develops more slowly
-occurs for a long period of time
-ie. TB, Hep B
Subacute Disease
-between acute and chronic
-ie. Subacute sclerosing panencephalitis
Latent Disease
-causative agent remains inactive for a certain time then becomes active to produce symptoms
-ie. Shingles
Herd Immunity
-an advantage of vaccination
-if most people in a population are immune
-outbreaks are limited, still susceptible people
Local Infection
-invading microorganisms are limited to a smaller region of the body
-ie. abscesses
Systemic (Generalized) Infection
-microorganisms are spread throughout the body by blood or lymph
-ie. measles
Focal Infection
-when a local infection enters a vessel and spreads to specific areas of the body
Sepsis
-toxic inflammatory condition
-arises from microbial spread via bacteria or toxins
Septicemia
-aka blood poisoning
-systemic infection arising from pathogen multiplication in the blood
Bacteremia
-the presence of bacteria in the blood
Toxemia
-presence of toxins in the blood
Viremia
-presence of viruses in the blood
Primary Infection
-an acute infection that causes the initial illness
Secondary Infection
-caused by an opportunistic pathogen after the primary infection has weakened the body’s defences
Subclinical Infection
-doesn’t cause any noticeable illness
-ie. Polio and Hep A (in some cases)
Predisposing Factor
-makes the body more susceptible to a disease
-alter the course and occurrence of the disease
Incubation Period
-between initial infection and first appearance of signs and symptoms
-may be variable
-some diseases can be spread during this phase
Prodromal Period
-relatively short
-follows period of incubation
-early, mild symptoms
-ie. aches
Period of Illness
-disease is most severe
-overt signs and symptoms
-WBC count may change
-if disease not treated, patient dies in this phase
Period of Decline
-signs and symptoms subside
-patient is vulnerable to secondary infection
Period of Convalescence
-person regains strength
-recovery has occurred
Reservoir of Infection
-a source of infection, where the organism survives till it finds a new host
Human Reservoirs
-principal living reservoir
-may have signs and symptoms or not
Carriers
-asymptomatic disease carriers
Zoonoses
-diseases that occur in animals that can be transmitted to humans
-ie. rabies, lyme disease
Nonliving Reservoirs
-ie. soil and water and food
-can carry Clostridium, Cholera, Salmonella
Contact Transmission
-spread of a disease agent by direct contact, indirect contact, or droplets
Direct Contact Transmission
-physical contact between source and host
-no intermediate object involved
-ie. kissing, touch, sex
Congenital Transmission
-transmission of disease from mother to fetus at birth
-via placenta or contact with blood
Indirect Contact Transmission
-agent is spread from reservoir to host via nonliving object
-ie. stethoscope
Fomite
nonliving object involved in the spread of an infection
Droplet Transmission
-microbes spread in droplet nuclei
-discharged by coughing, sneezing, laughing, talking
-travel less than 1m to host
Vehicle Transmission
-transmission of disease via a medium
-air, water, food, blood, body fluids
-ie. Salmonella
Airborne Transmission
-spread of agents in droplet nuclei in dust
-travel more than 1m
-ie. measles, TB
Waterborne Transmission
-contaminated or untreated sewage
-ie. cholera, shigellosis
Foodborne Transmission
-transmitted in foods that aren’t cooked, poorly refrigerated, prepared in unsanitary conditions
Vectors
animals that carry pathogens from one host to another
Mechanical Transmission
-the passive transport of the pathogen on the insects feet or other body parts
-commonly spread to food and then ingested
Biological Transmission
-active process
-bite, infected blood, pathogens reproduce in the vector
-or via feces or saliva
-ie. Zika virus, Malaria
Healthcare-associated Infections/Nosocomial Infections
-patients acquire while receiving treatment for other conditions
-8th leading cause of death in the US
Factors Contributing to HAIs
- many organisms in hospital
- weakened status of the host
- chain of transmission in hospitals
Compromised Host
-resistance to infection is impaired by disease
-broken skin or suppressed immune system
HAIs
-catheters
-surgical site infections
-UTIs
-ventilators
-C. diff
-bloodstream
-ventilation/water system
-via staff
-food
Universal Precaution
-designed to protect staff and patients
-standard and transmission-based precautions
Standard Precautions
-basic, minimum practices
-all levels of care
-gloves, masks, gowns, disinfection
Transmission Based Precautions
-used with individuals with known or suspected transmissible infections
Contact Precautions
-feces, urine, body fluids
-ie. Salmonella, C. diff
Droplet Precautions
-droplets spread short distanced
-ie. influenza, meningitis
Airborne Precautions
-long distance droplet nuclei
-ie. chicken pox, measles, TB
Emerging Infectious Diseases (EIDs)
-diseases that are new or changing
-many are zoonotic
Genetic Recombination
-new strains of E. coli and avian influenza (H5N1)
Evolution of Existing Microorganisms
-ie. a new serovar like V. cholerae O139
Unwarranted Use of Antibiotics and Pesticides
-growth of more resistant microbes and vectors that carry them
Global Warming
-increase survival and distribution of reservoirs and vectors
-ie. malaria
Modern Transportation
-known diseases spread to new places
-ie. Zika virus, West Nile
Human Travellers
-brought by insect vectors on travellers
-ie. Yellow fever
Animal Control
-increase in Lyme disease due to rising deer populations
Bioterrorism
-act of violence to produce death and disease
-ie. Anthrax
