EXAM 3: Path & Epidem 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
Pathogenesis
The process of disease development
Pathogen
A microorganism that can cause disease
Symptoms
Subjective characteristics of disease felt only by the patient
Syndrome
A group of symptoms that consistently occur together or a condition characterized by a set of associated symptoms
Signs
Objective manifestations of disease observed or measured by others
Epidemiology
The branch of medicine that deals with the incidence, distribution, and 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 region, or people
Sporadic Disease
An illness that occurs at irregular intervals; having no pattern or order in time
Outbreak
A sudden and unexpected increased disease incidence over the expected number of cases
Epidemic
An outbreak of disease that spreads rapidly and widely within a contiguous geographic area
Pandemic
An outbreak of disease that spreads rapidly and widely
List and describe the three types of microbial symbiotic relationships
draw out chart
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?
- 10^14 prokaryotic cells and only 10^13 is eukaryotic
- Organisms that colonize the body’s surfaces without normally causing disease
- Can be commensal, mutualistic, or pathogenic
Resident Microbiota
* Are part of normal microbiota throughout life
* Are mostly commensal
Transient Microbiota
* Found in some regions as resident microbiota
* Remain in the body for short period of time
* Cannot persist in the body
Competition from other microorganisms
Elimination by the body’s defense cells
Chemical or physical changes in the body
Acquisition of normal microbiota:
The womb is an axenic (free of microorganisms)
Microbiota begin to develop during birthing process
Much of one’s resident microbiota established during first months of life
Benefits:
Assist in various bodily functions (digestion in large intestine)
Can protect from pathogens that enter the body
Drug metabolism
Maintains structural integrity of gut
Immunomodulation
Differentiate between pathogens, opportunistic pathogens and non-pathogens
Opportunistic Pathogens:
Normal microbiota that cause disease under certain circumstances
- Introduction of normal microbiota into unusual site in body
- Immune suppression
- Immunocompromised
- Changes in the normal microbiota
——-> Changes in relative abundance may allow opportunity for a member to thrive and cause disease
——-> Broad spectrum antibiotics
Non-pathogenic:
Organisms that do not cause disease
Pathogenic:
Microorganisms that can cause disease in virtually any 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?
Four groups of transmission
1. Airborne Transmission
- Small particles that travel >1 meter
- Usually propelled from respiratory tract
2. Contact Transmission (direct contact or droplet)
- Large particles that travel <1 meter
- Coming together or touching of source/reservoir and host
3. Vehicle transmission (indirect contact/ water-borne/body fluid)
- Inanimate materials involved in pathogen transmission: Water, food and fomites
4. Vector-Borne transmission (biological host/mechanical)
- external and internal transmission
Portals of entry:
1. Skin
- pathogens can enter through openings or cuts
2. Mucous membranes
- Respiratory tract is the most common site of entry
3. Placenta
- Pathogens may cross the placenta and infect the fetus
4. Parenteral
- Pathogens deposited directly into tissues beneath the skin or mucous membranes. Ex: needlestick
Portals of exit:
- Ear (earwax)
- Eyes (tears)
Discuss reservoirs of infection. List and describe the three types
Def: sites where pathogens are maintained as a source of infection
- Animal reservoir
- Zoonoses (learning objective in itself so know this)
- Diseases naturally spread from animal host to humans
- EX: rabies
- Acquire zoonoses through various routes
- Direct contact with animal or its waste
- Eating animals
- Bloodsucking arthropods
- Human carriers
- Infected individuals who are asymptomatic but infective to others
- Some individuals eventually develop illness while others never get sick
- Healthy carriers may be protected by their immune system - Nonliving reservoir
- Soil, water, and food can be reservoirs of infection
- Presence of microorganisms often due to contamination by feces or urine
Describe zoonoses
Zoonoses
Diseases naturally spread from animal host to humans
EX: rabies, lyme disease
Acquire zoonoses through various routes
- Direct contact with animal or its waste
- Eating animals
- Bloodsucking arthropods
Humans are usually dead-end host to zoonotic pathogens
Explain the stages of disease
- Incubation:
Pathogen first enters body and begins to multiply
NO signs or symptoms - Prodromal period
General, non-specific signs and symptoms - 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
