Midterm2 Flashcards
What are Kochs postulates used for?
To prove the cause of an infectious disease
Kochs postulates
1) The same pathogen must be present in every case of the disease
2) The pathogen must be isolated from the disease host and grown in pure culture
3) the pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal.
4) The pathogen must be isolated from the inoculated animal and must be shown to be the original organism
Incidence
Describes the rate of development of a disease in a group over a period of time; new cases
♣
(Number of persons develop a disease/ total number at risk)*unit time
Prevalence
♣ Count of the # of person w/ disease
- Is the most frequently used measure in epidemiology
♣ New and old cases
(# of persons w/ a disease/total # in grp
Morbidity rate
o incidence of illness (disease) in a population. It includes both fatal and nonfatal diseases; could refer to either prevalence or incidence
Mortality rate
Incidence of death in a population
♣ (# of persons dead/ total # in grp)x unit time
Case fatality rate
the number of confirmed cases that died of the disease
Sporadic disease:
disease that occurs only occasionally
Endemic disease
disease constantly present in a population
Epidemic disease
disease acquired by many people in a given area in a short time
Pandemic disease
worldwide epidemic
Acute disease
symptoms develop rapidly but the disease lasts only a short time
Chronic disease
symptoms develop slowly
Subacute disease
intermediate btw acute and chronic
Latent disease
causative agent is inactive for a time but then activates and produces symptoms
Herd immunity
immunity in most of a population
Case definition
important and not trivial
Local infection
pathogens are limited to a small area of the body
Systemic (generalized) infection
an infection throughout the body
Focal infection
systemic infection that began as a local infection
Sepsis
Toxic inflammatory condition arising from the spread of microbes, especially bacteria or their toxins from a focus of infection
Bacteremia
bacteria in the blood
Septicemia
also known as blood poisoning growth of bacteria in the blood
Toxemia
toxins in the blood
Viremia
viruses in the blood
Primary infection
acute infection that causes the initial illness
Secondary infection
opportunistic infection after a primary infection
Subclinical disease
no noticeable signs or symptoms
Predisposing factors (make the body more susceptible to disease)
o Gender o Inherited traits such as the sickle cell gene o Climate and weather o Fatigue o Age o Lifestyle o Nutrition o Chemotherapy
- Development of Disease
o Incubation period: interval btw initial infection and first signs and symptoms
o Prodromal period: short period after incubation; early, mild symptoms
o Period of illness: disease is most severe
o Period of decline: signs and symptoms subside
o Period of convalescence: body returns to its pre-diseased state
o Human reservoirs
♣ Carriers may have unapparent infections or latent diseases
♣ By vaccinating youre changing the dynamic of sideade and provide immunity for the community
♣ Influenza virus that are similar enough to humans can sometimes make that cross
Animal reservoirs
Zoonoses are diseases transmitted from animals to humans
Nonliving reservoirs
♣ Soil and water
Food
Transmission
o Direct contact: requires close association btw the infected and a susceptible host
o Indirect contact: spreads to a host by a nonliving object called a fomite
o Droplet transmission: transmission via airborne droplets less than 1 meter (sneeze)
o Vehicle: transmission by an inaminate reservoir
♣ Waterborne, foodborne, airborne
Healthcare-associated infections
o Acquired while receiving treatment in a health care facility
♣ Also known as nosocomial infections
Emerging infectious diseases
diseases that are new, increasing in incidence, or show a potential to increase in the near futues
most zoonotic
of vital origin
likely vector borne
- Centers for Diesease control and prevention (CDC)
o Collects and analyzes epidemiological information in the US
o Morbidity and Mortality Weekly Report
o Notifiable infectious disease: diseases In which physicians are required to report ocurrence
Molecular strain-typing techniques; when to use
♣ Simplicity – simpler to execute and simpler to trainpeople to use(e.coli in brazil 1 month v 6)
♣ High throughput – capacity of tet to process a large number of specimens simultaneously
♣ Cost- widespread use of molecular bio reagents reduced costs. PCR have all the same reagents except for primers
♣ Appropriateness –
• The capacity of a test to addres epidemiologic problems not possible to address by conventional methods
• If conventional test possible then no need
• Often DNA sequences allow unambiguous identification of new ingectious agents and evolution of these agents
Molecular strain-typing techniques; how to select
♣ Typeabiliy: ability of a technique to generate an unambiguous result for an isolated test
♣ Reproducibility : ability to produce identical results
♣ Ease of interpretation: serve as stratum
♣ Ease of use: simplicity
♣ Stability: character us no subject to rapid evolution or lost from host
♣ Epidemiologic concordance: effectively group outbreak related strains
♣ Typing system concordance: molecular typing compares favorably with a previously validated test
♣ Validity: correctly predict or identify those who truy have the characteristics
