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communicable disease

Terms in this set (52)

epidemiological model triangle
host
agent
environment
describe agent
cause of disease
-need to consider:
1. type of agent, i.e. bacteria; virus; fungus; parasite
2. ability to cause injury or illness to a host
--infectivity
--pathogenicity
--virulence
--toxigenicity
--antigenicity
describe host
person or animal that harbors a disease-causing agent
-need to consider: exposure, host susceptibility, host response
describe environment
external conditions that influence the interaction between agent and host
-need to consider:
1. physical environment
2. biological environment
3. psychosocial environment
describe reservoir
-inanimate vs animate
reservoir: where an agent generally survives and multiplies
-inanimate: water, soil, food, etc
-animate: human (symptomatic; nonsymptomatic carrier); nonhuman/animal (zoonosis- an agent harbored by non-human vertebrate animal reservoirs)
-note: reservoir host refers to a host that serves as reservoir
modes of transmission
direct transmission
-contact transmission
-droplet transmission

indirect transmission
-vehicle-borne indirect transmission
-vector-borne indirect transmission
describe direct transmission
-Immediate transfer of agent from one human to another
-Limited to distance of 3 feet (~1 meter) or less
--Contact transmission: Direct physical transfer of microorganisms to a susceptible host from an infected or colonized person
--Droplet transmission: contact of the conjunctivae or the mucous membranes of nose or mouth of susceptible person with large-particle droplets (larger than 5 µm in size) containing microorganisms from person with disease or who is a carrier.
---Limited to distance of 3 feet or less because large droplets do not remain suspended in air and generally travel only short distances
...
Transferred at distance of > 3 feet
-Vehicle-borne indirect transmission
--Through animate objects (i.e. hands of healthcare workers can transmit pathogen to one patient from another)
--Through inanimate objects [fomites] (i.e. shared toys, inadequately cleaned stethoscopes)
--Through food (i.e. foodborne) or liquid (i.e. waterborne)
-Vector-borne indirect transmission
--usually arthropods (invertebrates)---Airborne Transmission
airborne droplet nuclei: small-particle residue - 5 µm or smaller in size - of evaporated droplets that can remain suspended in the air for longer periods of time
--dust particles containing the agent
patterns of transmission
unidirectional (nonhuman to human) vs bi-directional (nonhuman to human to nonhuman)

vertical (parent to child during fetal development, birth, or breastfeeding) vs horizontal (person to person)

endogenous (internal source) vs exogenous (external source)
def of latent period
period in which infectious agent has invaded a host, found conditions hospitable to replicate, and replicates before shedding
def of incubation period
the period between invasion of an agent and the appearance of the first symptoms
def of communicability period
the period of time the person is able to infect others (is contagious)
def of transmissability
estimations of the basic reproductive number (R nought [R0])
def of portals of entry and exit
the route an agent takes to enter/exit a host
typical routes of entry
mucous membranes
respiratory tract
skin
blood vessels
placenta
typical routes of exit
intestinal tract
respiratory tract
skin
blood
semen and vaginal fluids
wound exudate
incidence vs prevalence
-Incidence: number of new cases of disease in a given time period.
-Prevalence: number of ALL cases of disease at a given time.
endemic def
usual or expected occurrence of a disease in a given geographic area or population group.
outbreak def
unexpected occurrence of a disease in a limited geographic area or population over a limited period.
epidemic def
excess occurrence of a disease in a given geographic area or population group.
pandemic def
an epidemic that spreads over several countries or continents
-Usually occurs when:
1.A new agent is introduced into the human population.
2.The agent causes serious illness in humans.
3.The agent is able to be easily transmitted from person to person in a sustained manner.
prevention def
reduce or eliminate exposure or susceptibility to a disease.
control def
reduce incidence or prevalence of a disease at one point in time.
elimination def
control of a disease within a specific geographical area.
eradication def
reduce incidence worldwide to zero
surveillance
-Refers to an ongoing systematic collection, analysis, and interpretation of health data.

-The purpose is to detect, monitor, and control the spread of communicable diseases.
surveillance: organizations
-World Health Organization (WHO)
-U.S. Centers for Disease Control and Prevention (CDC)
--The Nationally Notifiable Diseases Surveillance System
--Early Aberration Reporting System
-State Health Departments
--Note: State health departments have the responsibility for monitoring and controlling communicable diseases within their respective states; they determine which diseases will be reported within their jurisdiction. Those lists might be longer than the CDC's list.
--State laws prevail over federal laws
-Local or regional health departments
-Healthcare provider
isolation vs quarantine
Isolation:
-Individual-level
-Generally for communicable diseases

Quarantine:
-Population-level
-Used across spectrum, from communicable disease to natural or chemical disasters, etc.
-3 levels
1.Shelter-in-place
2.Targeted restriction on movements and activities
3.Compulsory widespread restriction of movements and activities
theres an outbreak; now what?
-public health activities include
-Assemble an outbreak control team
-Determine coverage in affected and surrounding areas
-Enhance surveillance
-Inform the public and other authorities
-Educate case-patients and their contacts
-Proper case management
-Obtain specimens for lab confirmation
-Implement control activities to limit transmission- including vaccines, isolation/quarantine
-Collect detailed data on cases and outbreak response
natural immunity
bodys innate response
artificial immunity
body's response purposely induced
active immunity
body develops antibodies following exposure
natural active immunity
-how acquired
natural contact and infection with the antigen
natural active immunity
-length of resistance
may be temporary or permanent
passive immunity
antibodies transferred from another person or animal
natural passive immunity:
-how acquired
natural contact with antibody transplacentally or through colostrum and breast milk
natural passive immunity:
-length of resistance
temporary
artificial active immunity: how acquired
inoculation of antigen
artificial active immunity: length of resistance
may be temporary or permanent
artificial passive immunity: how acquired
inoculation of antibody or antitoxin
artificial passive immunity: length of resistance
temporary
cross immunity
antibodies to one disease protects from another disease
herd immunity
immunity among the majority protects those without immunity
immunization vs vaccination
Immunization: broad term
-Describes a process by which active or passive immunity to an infectious disease is induced or amplified.
--Immunizing agents can include vaccines as well as immune globulins or antitoxins.

Vaccination: narrower term
-Refers to administration of a vaccine or toxoid to confer active immunity by stimulating the body to produce its own antibodies.
types of vaccines
Live attenuated vaccines:
-Contain live weakened [attenuated] microorganisms

Inactivated vaccines:
-Contain killed [inactivated] microorganisms OR
-Toxins produced by microorganisms (toxoids)
considerations for vaccine storage, transport, and administration
-Cold chain
-Routes of administration, dosage, and sites
-Proper timing and spacing
-Hypersensitivity and contraindications
-Documentation: vaccine name and exp date, vaccine type, vaccine manufacturer, vaccine lot number, date of Vaccine Information Statement , and name, title, and address of person administering the vaccine.
-Vaccine safety and reporting of adverse events and vaccine-related injuries (VAERS)
considerations for vaccine effectiveness
-Primary vaccine failure: failure of vaccine to stimulate any immune response

-Secondary vaccine failure : waning of immunity following an initial immune response
adult immunization schedule
19 yo+: influenza (q yr), tetanus, diphtheria, pertussis (Td, Tdap), varicella
19-26 yo: HPV
19-21: meningococcal
60 yo+: zoster
19-59 yo: MMR
hepatitis A vaccine
-Increase interest in vaccine with Hep A outbreaks occurring since 2012

Who Should Receive the Vaccine?
-All children at age 1 year
-Persons who are at increased risk for infection
-Persons who are at increased risk for complications from hepatitis A
-Any person wishing to obtain immunity (protection)
COVID-19 vaccine
-Pfizer- two shots, 21 days apart
-Moderna- two shots, 28 days apart
-Unknown whether annual needed
-For 16 years and older
-Contraindicated:
--Severe allergic reaction to shot #1
--Allergic to polyethylene glycol (PEG) or polysorbate.
-Common SEs: soreness, swelling at site
-Systemic SEs most common after 2nd shot: chills, fatigue, headache
vaccines: word of caution
-Information and recommendations on immunizations and vaccine usage change regularly
-Vaccine Information Statements (VISs) that explain the benefits and risks must be given out before vaccine is administered—a federal law!!
influenza vaccine
-Protects against the influenza viruses that research indicates will be most common during the upcoming season.
-Trivalent vaccines- traditional flu vaccines; protects against influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus.
-Quadrivalent vaccines- protect against the same viruses as the trivalent vaccine and an additional B virus.
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