Concepts of infectious disease Flashcards
infectious disease
illness caused by a pathogen
true pathogen
a disease causing organism; when in contact with the pathogen it WILL cause disease
opportunistic pathogen
will cause disease only if circumstances within the host change
host
houses the pathogen
sporadic cases of disease
isolated infections in a given population or region
endemic cases of disease
infections are routinely detected in a given population or region
epidemic
widespread disease outbreak in a particular region during a specific time frame
pandemic
an epidemic that has spread to numerous countries
emerging pathogens
- newly identified pathogens
- previously unknown to humans
- ex. COVID-19
reemerging pathogens
- infectious agent that was under control, but now is resurfacing
- ex. antibiotic resistant strains of bacteria
zoonotic diseases
- spread by animals
- humans are accidental, dead-end hosts
- ~60% of emerging infections since 1970’s
what are the 6 groups of pathogens
1.helminths
2. protozoans
3. fungi
4. bacteria
5. viruses
6. prions
noncommunicable diseases
not spread from person to person
communicable diseases
does transmit from person to person
contagious
easily transmitted from one host to the next
active infection
patient is showing signs and symptoms
signs
objective indicators of disease, can be measured and verified
symptoms
sensed by the patient, subjective; cannot be measured
latent infection
host has no signs or symptoms
acute infection
sick for a small amount of time and eventually recover
persistent chronic infection
have an acute phase initially but infection doesnt go away; may have signs/symptoms ocasionally
persistent latent infection
have an acute phase initially, infection then goes away and flares up occasionally
Koch’s postulates of disease
the four criteria used to evaluate what pathogen is causative a agent of a particular disease
1. same organism is present in every case of disease
2. organism must be isolated from diseased host and grown as pure culture
3. organism should cause disease when introduced into susceptible host
4. organism must then be re-isolated from new, diseased host
limitations of koch’s postulates
- doesnt apply to non-infectious diseases
- pure culture problem
- obligate intracellular pathogens
- human-only pathogens
- asymptomatic or latent diseases
reservoir
animate or inanimate habitat where pathogen is naturally found
source
disseminates the agent from reservoir to new hosts **intermediate
direct contact transmission
- person to person
- animal
- environment
- vertical (pregnancy)
indirect contact transmission
- airborne
- vehicle (contaminated objects)
- vector-biological (insect bite)
- vector-mechanical (pathogen is carried by another organism/object)
infectivity
how good an infectious agent is at establishing an infection
virulence
severity of disease following infection
pathogenicity
general ability of agent to cause disease
five stages of infectious disease
- incubation period
- prodromal phase
- acute phase
- period of decline
- convalescent phase
chronic carriers
carry the disease and show symptoms chronically and transmit to other host
asymptomatic carriers
carry the disease and transmit it to others and cause others to be symptomatic
epidemiology
- the study of what is upon people
- describes the nature, cause, and extent of new or existing diseases in a population
- intervene to protect and improve health in populations
epidemiological triangle
a tool for seeing how infectious disease spread
- etiological agent
- host factors
- environmental factors
etiological agent
fungi, bacteria, virus, or parasite
environmental factors
climate, geographical location, availability of transmitting vector, water source, food source, etc
host factors
general health, sex, lifestyle, age, ethnicity, occupation, etc
strategies to break the epidemiological triangle
- public education
- quarantine
- vector control
- role of public health system
ignaz semmelweis
- hungarian physician
- noticed childbed fever
- recommended hand washing
joseph lister
- started aseptic surgery techniques
- washing instruments with carbolic acid
- encouraged healing, prevented pus forming
florence nightingale
- aseptic technique in nursing practices
- founder of modern nursing
healthcare-acquired infections
- nosocomial infections
- diseases that develop from healthcare intervention
- direct or indirect contact
- localized or systemic
- medical devices or procedure
- biofilms
- surveillance, prevention, and control programs
superbug HAIs
- drug-resistant pathogens
- routine testing when hospitalized
CDCs national notifiable disease surveillance system
reportable and notifiable diseases are kept track of on a national and international level
outbreak
- increase in number of cases of disease
- limited to community or particular geographic area
- normally caused by an infection caused by contact
epidemic
- sudden increase in number of disease cases
- infections are above what is normally expected in population in that area
- can affect people within a short period of time
pandemic
- disease usually affects a large number of people
- has spread across several countries or continents
incubation period
the time between infection and the development of the earliest symptoms
prodromal phase
early symptoms develop
acute phase
the peak of the disease
period of decline
replication of the infectious agent is brought under control; symptoms start to resolve
convalescent phase
the patient recovers; in some cases the pathogen is kept latent in the patient
