Chapter 9 continued Flashcards
Bacteria
Prokaryotic, unicellular
- some are obligate intracellular parasites some are free living
ex: streptococcal, staphylococcal, tetanus, pneumonia, typhus
Viruses
Noncellular, nonliving, infectious particles
- contain DNA/RNA
- smaller than prokaryotes
ex: AIDS, influenza, hepatitis, polio, smallpox
Prions
infectious proteins
- NOT cells
- no DNA/RNA
- cause certain proteins in host brain to fold incorrectly
ex: CJD, Kuru, chronic wasting disease (elk,deer,moose)
disease source
the person, animal, object, or substance that disseminates/passes the infectious agent to the host
-can be the same as reservoir
Reservoir
animate/inanimate habitat that the infectious pathogen is naturally found in.
Endogenous Source
infectious pathogen came from host’s own body
ex: misplaced microbiota (skin microbiota entering through wound)
disrupted microbiota & opportunistic pathogens (vaginal yeast infection)
exogenous source
pathogen came from source external to host’s own body
- Environmental: contaminated food/water, soil, med equipment
- Animals: zoonotic disease spread to human
- Humans: communicable diseases
Disease transmission
how the pathogen is spread to the host
Direct contact transmission
host physically comes into contact with the source of pathogen
- person-person: saliva, touching, sex
- animal-person: bite, scratch, zoonotic
- environment-person: swimming, soil
- Vertical: mother to child in utero, breastmilk, vaginal delivery
indirect contact transmission
pathogen spreads with out host’s direct physical contact to the source
- airborne: pathogen enters through respiratory route
- vehicle: pathogen introduced through host’s contact to contaminated object
- biological vector: part of pathogen’s lifecycle is in an animal and other part in human (mosquito bite, tick bite)
- mechanical vector: pathogens lifecycle is outside host and it catches a ride( roaches,flies)
5 stages of infectious disease
- incubation period
- prodromal
- acute
- decline
- convalescence
incubation period
time of exposure to infectious pathogen til the 1st sign of symptoms
- varies by person
- varies by pathogen
- challenging to determine incubation time due to variables
- disease can spread
prodromal period
early symptoms/signs develop
- mild symptoms/signs due to activation of immune system
- pathogen continues multiplying
- infection can still be spread
Acute period
full experience of signs/symptoms
- symptomatic
- asymptomatic
- some diseases that are asymptomatic on one host can be deadly in another
Decline period
pathogen replication decreases
- host begins to feel better
- patients usually stop antibiotics during this period causing the infection to return full force or the pathogen to mutate and become antibiotic resistant
Convalescence Period
pathogen is usually eliminated at this stage but can be kept latent in the host’s body (usually viruses)
-disease can reactivate at a later time if latent in the body
chronic carrier
mostly asymptomatic with sporadic recurrences
-can infect others ( HSV2)
asymptomatic carrier
pathogen stays latent in carrier showing no symptoms
-can infect others (streptococcus pyrogenes)
epidemiology
“the study of what is upon the people”
Hippocrates wat the 1st epidemiologist
-understand and prevent illness in communities
Goals of epidemiology
- describe the nature, cause, and extent of new/existing diseases in populations
- intervene to protect and improve health in populations
examples of host factors in epidemiological triangle
general health, sex, lifestyle, age, ethnicity, occupation
examples of environmental factors in epidemiological triangle
climate, geographical location, availability of transmitting vector, water source, food source
how can epidemiological triangle be broken
education, quarantine, vector control
roles of public health
investigates, diagnoses, prevents, and works to reduce health related problems in community
rate
measures occurrence of an event over time
ratio
presents the occurrence of one group compared with another group
ex: in US the people age 65^ are 0.77male/female
proportion
a percentage of a whole
ex: 80 out of 100 women/80% of women with gonorrhea are asymptomatic
why are epidemiological measurements useful
they provide insight as to where public health campaigns or prevention efforts are needed most
measures of frequency
gives information about occurrences of a disease in a population during a certain period of time
- reveals degree of morbidity (existence)
- prevalence rate
prevelance rate
describes morbidity in a given population during a specific time
- total # of cases in a given time divided by total #of people in the defined population during that same time
- not a measure of how dangerous the disease is
- impacted by incidence rate and duration
incidence rate
the number of new cases in a defined population during a defined time frame
-new cases in a defined pop during specific time divided by susceptible hosts in the population during the same time
duration
how long the infection lasts
morbidity
existence of the disease
measures of association
tell what factors may be linked with cases of the disease showing who may be at risk for developing an illness.
- helps providers diagnose correctly for patients showing general signs/symptoms
ex: pt living in certain area presents with joint pain and fatigue, doc will ask if pt spends much time outdoors or noticed any tick bites bc Lyme disease is associated with tick bites
mortality rate
most common association measure
-the number of deaths during a specific time period
crude mortality
general death rate in a population, not determined based on specific causes of death
cause-specific mortality rate
deaths due to a specific cause, in a given population, during a specified period
infant mortality rate
death rate of children under age 1, as compared to number of live births
maternal mortality rate
maternal deaths per 100,000 live births, from any cause related to pregnancy or management of pregnancy
case fatality rate
percentage of people with a particular diagnosis who die in a specified time period after diagnosis
correlation does not imply causation
just because 2 things occur around the same time or place doesn’t make the variables correlated or linked
ex: autism spikes and vaccines
descriptive epidemiology
who is infected, where cases occur, and when cases occur
-goal is to describe occurrence/distribution of disease so a hypothesis about causes, prevention, treatment can be developed and tested
analytical epidemiology
investigates what caused the disease, why people get it, and how to prevent or treat the disease
