Chapter 9: Principles of Infectious Disease and Epidemiology Flashcards
Sporadic Cases
isloated infections in a particular population
Endemic Infections
rountinely detected in a population or region (cold virus)
Epidemic
widespread diasese outbreak in a particular region during a specific time frame
Pandemic
occurs if an epidemic spreads to numerous countries
Emerging Pathogen
include newly identified agents as well as pathogens that previously caused only sporadic cases (SARS-CoV-2) or exhibit an expanded geograhical districubtion (ziki virus)
Reemerging Pathogen
an infectious agent that was undercontrol but is now resurfacing
Noncommunicable diseases
do not spread from person to person
Communicable Diseases
transmits from human to human
Contagious Diseases
easily transmitted from one host to the next
Symptomatic
during an active infection the patient exhibits signs and symptoms
Signs
objective indicators of disease that can be measured or verified; fever, rash, etc
Symptoms
sensed by the patient and are subjective rather than precisely mesaurable; pain fatigue and nausa etc
Acute Diseases
have a rapid onset and progression
Chronic Diseases
have a slower onset and progression
Kochs Postulates
same organism must be present in ever case of the disease; the organism must be isolated from the diseased host and grown as a pure culture; isolated organism should cause disease in question when inoculated in a susceptible host; organism must then be reisolated from the inoculated diseased animal
Limitations of Kochs Postulates
do not apply to noninfectious disease; certain infectious disease cannot be isolated; some microbes become attenuated in pure cultures; some microbes do nt infect nonhuman hosts; not easily applied to infectious agents that primarily cause latent disease
Reservoirs
are an animate or inanimate habitat where the pathogen is naturally found
Sources
disseminate infectious agent from the reservoir to new hosts
Endogenous Source
means the pathogen came from the hosts own body; like bacteria on skin entering a surgical incision or yeast in vagina proliferting when antibiotics kill off normal bacteria
Exogenous Source
means the pathogen is external to the host; contaminated food, zoonotic disease, transmitting between humans
Mode of Transmission
how the pathogen spreads to a host; generally classed as direct contact and indirect contact
Direct Contact
host comes into physical contact with the source of the pathogen; such as a bite, touching, kissing, going in a pond
Vertical Transmission
specialized form of diret contact; occurs when pathogen passes from mother to offspring during pregnancy (in utero), delivery (transcervical) or breatfeeding (post partum)
Indirect Contact
pathogen spreads without direct physical contact with the source; three main categories- airborne transmission, vehicle transmission, and vector transmission
Airborne Transmission
pathogen enters through respiratory route; usually occurs by inhaling pathogen-laden respiratory droplets
Vehicle Transmission
pathogen is found on contaminted fomite (doorknowbs, needles, sheets, food)
Vector Transmission
transmission by vectors (arthropods)
Biological Vector
vector organism has a role in the pathogens life cycle; ticks mosquitoes
Mechanical Vector
vector spreads disease without being integral to a pathogens life cycle; flies, rodents and cockroaches
Infectivity
describes how good an infectious agent is at establising an infection
Pathogenicity
is the general ability of an infectious agent to cause disease
Virulence
describes severity of disease following infection
Five Basic Stages of Disease Progression
incubation period to prodromal phase to acute phase to period of decline to convalescent phase
Incubation Perid
time between infection and the development of disease symptoms; could be hours or years depending on the disease
Prodromal Phase
patient starts to feel run down and may have mild symptoms
Acute Phase
patient experiences full blown classical symptoms of the disease; know as symptomatic case or clincal infection
Period of Decline
pathogen replication decreases; patient begins to feel better; not all patients experience this pahse because some patients are killed by the pathogen; sometimes patients on antibiotics may prematuraly stop taking their medication and infection may come back
Convalescent Period
elemination of pathogen from body; sometimes pathogen is harbored indefinietly; can go into dormancy; chronic carrier; asymptomatic carriers
Epidemiology
study of what is upon the people; focuses on disease (infectious and noninfeectious) in populations; aims to understand and precent illness in communities
Two Goals of Epidemiology
describe the nature, cause and extent of new or existing diseases in populations; intervene to protect and improve health in populations
Public Education
central to breaking the epidemiological triangle; include vaccine campaigns, promotion of prenatal and breastfeeding, and eduation about sexually transmitted diseases; helps people understand their role in preventing development of drug resistant pathogens
Quaratine
period of confinement away from general population; but for diseases with long incubation period quarantine may be impractical or inhumane; CDC can quarantine anyone entering/in US with cholera, diptheria, TB, plague, small pox, yellow fever, viral hemorrhagic fevers, SARS CoV 1 and 2, and certain influenza strains
Vector Control
limiting the number of biological vectors helps prevent the spread of many dangerous infectious diseases; arboviruses, lyme disease, malaria
Rate
used to meausre the occurence of an event over time
Ratio
occurence of an event in one group as compared to another group
Proportion
percentage of a whole
Measures of Frequency
give information about the occurence of a disease in a population during a certain period of time
Population
any defined group of people
Morbidity
existence of a disease in a population
Prevelance
morbidity in a given population during a specific time; impacted by incidence rate and duration
Incidence Rate
number of new cases in a defined population during a defined time frame
Duration
How long the infection lasts
Measures of Association
tell us what factors may be linked with cases of the disease and subsequently who might be at risk; allows public health officials to warn people about how to avoid certian infections; allows healthcare providers to arriave at the correct daignosis more quickly
Crude Mortality Rate
general death rate in a population, not determined based on specific casues 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 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
Descriptive Epidemiology
help characterize health problems, identify at risk population and provide a map for allocating resources; characterizes health problems, identifies at risk populations, does NOT reveal the cause of disease, includes correlation studies, case reports and cross sectional studies
Analytical Epidemiology
uncovers who is infected, where cases occur, and when cases occur; goal is to describe the occurence and distribution of disease; yields a testable hypothesis; analytical studies test the validity of the hypothesis
Correlation Studies
ecological studies; search for associations between an exposire and the development of a disease; such as examining the associatino between fluoridated water and cavities
Case Reports
individual or group records of a disease; connect between clinical medicine and epidemiology
Cross Sectional Studies
evaluate exposure and the development of disease across a defined population at a single point in time; often use surveys to determine prevalence of a disease
Analytical Studies
tend to be more challenging and expensive than descrptive studies; usually require more expensive lab equipment and /or long term patient data tracking; can include obserationla and expiremental studies
Observational Studies
do NOT involve administering intervention, a treatment, or an exposure for a disease; watch and collect data on cases that exist, used to exist, or develop over time; develop study groups based on exposure (smokers v. nonsmokers); measure risk for developing a certain disease when certain risk factors are present
Experimental Studies
allow the researcher to change variables and determine the effect of the change on the outcome; used to determine the effectiveness of a treatment of preventive meausre; expiremental studies control variables (blinding, randomization, placebos, etc); such as clinical trials
Ignaz Semmelweis
worked at two materinity wards; one staffed by midwives and one staffed by physicians and studnets; different mortality rates; autopsies were performed by students/physicians and they did not wash up inbetween; so semmelweis started washing in between and discovered lower mortality rates
Hospital Epidemiology
onvolves the surveillance, prevention, and control of helathcare-acquired infections; diseases that develop from a healthcare intervention
Common HAIs
contaminated medical devices and healthcare workers hands are the most common sources; medical devices, hospital personnel; clostridiodes difficle GI infections; UTI; surgical wounds; MRSA bacteremia; intravascular device; pneumonia
Basic Preventive Measures for HAIs
hand washing, consistent use of personal protective wear, environmental sanitization, equipment sterilization, limiting patient transport, single patient equipment use, patient isolation
“Superbug”
HAIs drug resistent pathogens often orginiate in healthcare settings due to extensive antibiotic use
National Notifiable Diseases Surveillance System
NNDSS; network of local hospitals, laboratories and private helathcare providers; monitor and report certain diseases; states have laws requiring reports of certain diseases to a local health authority; the diseases on a state or local tracking list are reportable diseases
After a reportable disease is diagnosed…
it is documented per state or local rules ; case reports trickle up the local and state reporting chain to the CDC; national statistics are compiled
Morbidity and Mortality Weekly Report
MMWR; updates health officials and care providers on US health issues; provides summaries of health watches and a running report for selected notifiable diseases
Emerging Diseases
new or newly identified infections in a population; such as Ebola, HIV, H1N1, Zika, Covid 19
Factors Contributing to Increase of Emerging Diseases
population crowding, poverty, tropical climates, diverse wildlife, deforestation, urbanization
Reemerging Diseases
were previously under control, but are now showing increased incidence; associated with pathogens that have evolved increased virulence (antibiotic resistance ex)
Eradication
there are no longer any cases of it anywhere in the world; only been done once i 1977 with smallpoz; polio and guinea worm are close
Tuskegee Symphilis Experiment
1932-1972; long term effects of syphilis in a group of poor african american men; study participants were never informated they had the disease; misled about the reasons for ongoing tests and the disease; researchers actively prevented participants form receiving penicllin
Genetic Information Nondiscrimination Act
GINA; cannot be denied helth insurance due to genetics; does NOT prevent denial of long term care insurance, life insuracne or disability
