Exam 3: Pathogenesis and epidemiology Flashcards
Infectious disease
A transmittable, clinically relevant, illness
Morbidity
The state of being diseased or unhealthy, often times within a population
Mortality
Death, often times within a population
Pathogen
A microorganism that can cause disease
Symptoms
Subjective characteristics of disease felt only by the patient
Pathogenesis
The process of disease development
Signs
Objective manifestations of disease observed or measured by others
Syndrome
A group of symptoms that consistently occur together or a condition characterized by a set of associated symptoms
Epidemiology
The branch of medicine that deals with the incidence, distribution, and possible control of diseases
Incidence
Number of new cases of a disease in a given area during a given period of time
Prevalence
Number of total cases of a disease in a given area during a given period of time
Endemic
An illness that is prevalent in or peculiar to a particular locality region, or people
Sporadic Disease
An illness that occurs at irregular intervals; having no pattern or order in time.
Outbreak
A sudden and unexpected increase disease incidence over the expected number of cases
Pandemic
An outbreak of disease that spreads rapidly and widely
Epidemic
An outbreak of disease that spreads rapidly and widely within a contiguous geographic area.
List and describe the three types of microbial symbiotic relationships
mutualism: relationship where both involved benefit (Bacteria in human colon)
Commensalism: relationship where one organism benefits and the other is unaffected (staphylococcus on skin)
Parasitism: Relationship that benefits one and harms the other (tuberculosis bacteria in human lung)
Discuss normal microbiota. Where are they found? What benefits can they provide?
● Organisms that colonize the body’s surfaces without usually causing disease
● Found in areas exposed to external environment: skin mucous membranes, GI tract, respiratory
tract
● Types:
○ Resident microbiota: part of the normal flora throughout life and are mostly commensal
○ Transient microbiota: temporary colonizers that cannot persist because of competition
with resident microbes, immune system, or changes in the body
● Benefits
○ Compete with pathogens in niches to prevent colonization
○ Aid in digestion and produce essential vitamins
○ Stimulate immune system and provide defense mechanisms to help body recognize
harmful invader
Differentiate between pathogens, opportunistic pathogens and non-pathogens
● Pathogens: cause disease in healthy hosts, breach defenses, survive in hostile environments
○ Ex: mycobacterium tuberculosis
● Opportunistic pathogens: cause disease when the host’s immune defenses are compromised or
when they invade unusual sites in the body
○ E. coli causing UTI when displaced from intestines
● Non-pathogens: do not typically cause disease, even in a healthy host, coexist with host harmlessly
or even benefit host
Describe how microorganisms enter and exit the human host. What are the portals of entry and exit? How is infection transmitted to new host?
● Portals of entry:
○ Skin: cuts, abrasions, direct penetration
○ Mucous membranes:
■ respiratory tract most common entry point
■ Pathogens enter GI tract through ingestion
■ Urogenital tract infection through sexual contact or compromised mucosal
barriers
○ Placenta: cross placenta and infect fetus
○ Parenteral route: usually unnatural; injecting pathogens directly into tissues through needle
sticks, insect bites, trauma, etc.
● Portals of exit:
○ respiratory/salivary portals: coughing, sneezing, talking
○ GI tract: feces, vomit
○ Urogenital tract: urine, semen, vaginal secretions
○ Blood: infected blood transmitted through insect vectors/shared needles
Discuss reservoirs of infection. List and describe the three types
● Sites where pathogens are maintained as a source of infection, most cannot survive outside host
● Three types:
○ Animal reservoir: zoonoses (animals that harbor pathogens that can infect humans)
■ Acquired through direct contact with animal or its waste, eating animal, or via
vectors like insects
■ Rabies, lyme disease
○ Human carriers: infected individuals who are asymptomatic but infective to others
■ Some individuals eventually get ill while others never do
■ Healthy carriers protected by their immune system
○ Nonliving reservoir: pathogens persist in soil, water, food, etc.
■ Presence of microorganisms due to contamination by feces/urine
■ Cholera in water
Describe zoonoses.
● Diseases naturally spread from animal host to humans
● Acquired through:
○ Direct contact with animal or its waste
○ Eating animals or contaminated animal products (undercooked meat)
○ Bloodsucking arthropods
■ Vector transmission
● Humans are dead-end host to zoonotic
Explain the stages of disease
Incubation:
-Pathogen first enters the body and begins to multiply
-No signs or symptoms
Prodromal period
-General, non-specific signs and symptoms
-EX: not feeling right in the morning (fatigue or illness?)
Illness
-Infection-specific and most severe signs and symptoms appear
Decline
-Immune system responds
-Declining signs and symptoms
Convalescence
-Pathogen is almost fully out of the body
-No signs or symptoms
Compare and contrast the terms incidence and prevalence
Incidence
-Number of new cases of a disease in a given area during a given period of time
Prevalence
-Number of total cases of a disease in a given area during a given period of time
*They both refer to ways we track and measure the occurrence of diseases
Explain the role of international and government agencies in disease control and prevention
● World Health Organization (WHO)
○ Leads global efforts to monitor disease outbreaks
○ Provide aid to affected areas
○ Implement disease prevention programs
● Department of Health and Human Services (HHS)
● US Public Health Service (PHS)
○ Primary division of HHS
○ US PHS Commissioned Corps is one of 8 uniformed services in the US
○ Federal agencies
■ Centers for Disease Control and Prevention (CDC)
● Tracks disease outbreaks
● Investigates public health threats
● Issues guidelines for controlling disease spread in US
■ Food and Drug Administration (FDA)
● Certify any pharmaceutical or medical device
■ National Institutes of Health (NIH)
● Biomedical research arm of US government
● Department of Homeland Security (DHS)
○ Bioterrorism
○ Federal emergency management agency (FEMA)
● Strategic national stockpile program (SNS)
● Biomedical advanced research development authority (BARDA) and project bioshield
○ BARDA is separate communicator between agencies and is independent from PHS
● Local and state agencies
○ Implement health measures such as vaccination programs
○ Public health education
○ Response to disease outbreaks within their jurisdictions
Compare and contrast endemic, epidemic and pandemic.
Endemic: an illness that is prevalent in or peculiar to a particular locality region or people
Epidemic: an outbreak of disease that spreads rapidly and widely within a contagious geographic area
pandemic: an outbreak of disease that spreads rapidly and widely
*they are similar in the way that they all refer to the ways in which disease affects a group of humans
Define nosocomial infection and discuss contributing factors
● Infection acquired in a hospital or healthcare setting
● Contributing factors:
○ Exogenous infections: acquired from healthcare environment
○ Endogenous infections: arising from patient’s normal microbiota due to changes in
healthcare environment like broad spectrum antibiotics
○ Iatrogenic infections: result from medical procedures such as surgeries or catheter insertion
○ Additional: poor hygiene practices, antibiotic resistance, invasive procedures
How is infection transmitted to new host?
● Airborne transmission: pathogen suspended in air and travels >1 meter
○ Droplet nuclei can remain airborne for extended periods
○ sneezing
● Contact transmission: person-to-person transmission through physical interaction
○ Touching, kissing, sexual contact, animal-to person transmission
● Vehicle transmission: spread of pathogens via contaminated inanimate objects
○ Fomite: object that provides vehicle transmission, common in healthcare settings
○ Food, water, medical equipment
● Vector-borne transmission
○ Mechanical vectors: passive transport of pathogens on vector’s body
■ Flies carrying pathogens on their feet
○ Biological vectors: pathogen undergoes part of its life cycle inside vector
■ Mosquitoes, malaria
○ External
■ Passive carriage of pathogen on body of vector
■ No growth of pathogen during transmission
○ Internal
■ Vector carries
■ Harborage transmission: pathogen does not change within vector
■ Biologic transmission: pathogen changes within vector
List specific types of virulence factors. Discuss how they work and how they influence pathogenesis.
● Pathogenicity: ability of microorganism to cause disease
● Virulence: degree of pathogenicity, contribute to pathogenicity
● Types:
○ Adhesion: fimbriae or capsules for ex attach to host cells and tissues
○ Toxins
■ Exotoxins: soluble proteins secreted by bacteria that damage tissue
■ Endotoxins: released upon death and trigger strong inflammatory responses; LPS in
outer membrane of gram-negative bacteria
○ Enzymes: help pathogens invade tissues and evade immune system
○ Antiphagocytic factors: prevent destruction by host immune cells
