Epidemic Simulation <3 Flashcards
Epidemiology
study of causes, occurrence, transmission, distribution, and prevention of diseases in a population
Occurrence of disease
Common source epidemic & Propagated source epidemic
Common source epidemic
when the source of an outbreak is contaminated water, food, heating or cooling system of a building, and infects many people at one time
Propagated source epidemic
a disease transmitted from person-to-person
Index case (first case reported)
applies to propagated transmission only
Point prevalence
the fraction of the population that has the disease at a point in time
Incidence rate
the fraction of the population that contracts the disease over a specific period of time
Infectious diseases - transmissible (communicable) diseases
caused by entrance, growth, and multiplication of micro-organisms in the body
Infectious diseases include…
some viruses, bacteria, fungi, protozoa, multicellular parasites, and aberrant proteins known as prions
3 types of disease transmission
direct contact, indirect contact via formite or vector, vehicle, and droplet transmission
Direct contact transmission
person-to-person; physical contact like touching, kissing, sexual intercourse
Indirect contact transmission
fomite - inanimate objects like:
-surgical instruments
-respiratory ventilators
-contaminated syringes
vectors - organisms that transmit, but do not cause disease
Classification of vectors:
Mechanical: housefly
Biological: mosquitoes, ticks, fleas, and lice
Vehicle transmission
infectious agent transferred to a person by ways other than physical contact (food, water, or air)
Examples of food-borne diseases
contaminated foods: H. pylori, hepatitis A
improperly cooked foods: parasitic infections
Droplet transmission:
a type of vehicle transmission; air-borne or microbial aerosol
Examples of droplet transmission
small residues that remain after the evaporation of liquid droplets released from an infected host
dust particles that may originate from floor, clothing, bed sheets, or contaminated floors
Most effective way to prevent spread of infectious disease
washing one’s hands
Patterns of infection
systemic (general), primary, secondary, nosocomial, and subclinical
Systemic (general) infections
spread throughout the body via the blood and/or lymph system
Primary infection
an acute infection that causes the disease
Secondary infection
occurs when an opportunistic pathogen is able to infect the host due to its weakened condition
AIDS patients offen suffer…
secondary infections such as Pneumocystitis pneumonia and tuberculosis
Nosocomial infection
hospital-acquired infection
Subclinical (unapparent) infection
does not have any noticeable clinical symptoms or signs
Symptoms are…
subjective changes in body function:
-pain
-headache
-heartburn
Signs are…
objective changes that a physician can observe, feel, or measure
Syndrome
a particular group of symptoms and signs associated with a certain disease
Communicable diseases
can be spread from one person to the next
Examples of communicable diseases
chicken pox (varicella), measles, genital herpes, tuberculosis etc.
Contagious diseases are…
easily transmitted (highly communicable) from one person to the next
Non-communicable diseases
do not spread from one person to the next
ex. tetanus (clostridium tetani) & anthrax (Bacillus anthracis)
Morbidity (sickness)
number of susceptible people who have the disease with a defined population during a specific time period
Mortality (death)
number of people who die from a specific disease out of the total population affected with that disease in a specific time period
Morbidity and Mortality Weekly Report (MMWR) by the CDC
a publication about the occurrence of 26 notifiable diseases from U.S. and its territories
Aerobic
Organisms that require oxygen to thrive
Aerotolerant organisms
can survive in presence of oxygen but are anaerobic bc they don’t use it as a terminal electron acceptor
Facultative anaerobes
can grow w or wo oxygen
Microaerophiles
Require low levels of oxygen to survive (i.e., are poisoned by high concentrations of oxygen)
Superoxid dismutase (SOD) enzyme and catalase enzyme
released by bacteria that possess an ETC
capable of breaking down the superoxidate radical (O2) and hydrogen perioxide (H2O2)
Antigen (Ag)
a substance capable of eliciting an immune response
Antibody (Ab)
immunoglobulin; a protein molecule produced by B lymphocytes in response to a specific antigen
Agglutination
clumping of particles; serves as evidence of antigen-antibody reaction
highly sensitive & may be used to detect presence of antibody or antigen in a sample
Direct agglutination
relies on the combination of antibodies and naturally particulate antigens
e.g., slide agglutination (samples of antigen and antiserum are mixed pm a microscope slide and allowed to react
Direct agglutination is used to…
diagnose some diseases, determine if pt has been exposed to a certain pathogen, and in determining the blood type
Indirect agglutination
relies on artificially constructive systems in which agglutination will occur
e.g., coating particles (such as RBCs or latex microspheres) with either Ab or Ag
Indirect agglutination is used…
in some pregnancy tests as well as in diagnosing diseases like HIV
Slide agglutination
A direct agglutination test that shows visible clumps (agglutinates) are formed when particulate antigens bind with antibodies
Slide agglutination kits…
diff kits provide for testing of different bacterial species
Slide agglutination results
Kit: Staphylococcus aureus
Clumping - presence of black particles - indicates a (+) result of S. aureus
No clumping indicates a (-) results of Staphylococcus epidermidis
Catalase test
differentiates bacteria based upon their ability to use aerobic or anaerobic respiration, specifically whether or not there is an ETC (electron transport chain)
The ETC is composed of…
molecules capable of accepting and donate electrons which alternate between the oxidized and reduced forms, passing electrons down the chain to the final electron acceptor (O2)
The energy lost by electrons in the sequential transfer is used to…
perform oxidative phosphorylation
Flavoprotein
is an ETC carrier molecule that can pass electrons directly to oxygen, creating two highly potent cellular toxins - hydrogen peroxide (H2O2) and superoxide radical (O2)
Organisms that produce the toxins, H2O2 and O2, also
produce enzymes capable of breaking them down. Catalase converts hydrogen peroxide into water and gaseous oxygen. Superoxide dsimutase catalyzes conversion of superoxide radicals to hydrogen peroxide
Superoxide Dismutase (SOD)
an enzyme produced by aerobic bacteria to deal with the more toxic superoxide radical (O2)
SOD 2O2 + 2H ---------------> H202 + O2
Catalase
an enzyme produced by aerobes, micro-aerophiles, and facultative anaerobes to deal toxic hydrogen peroxide (H2O2)
CATALSE
2H2O2 ——————–> 2H2O + O2
Catalase Test
Add H2O2 and check for bubbles
means oxygen is produced bc catalase worked upon the hydrogen peroxide
Catalase Test Results
Staphylococcus (catalase +)
Enterococcus & Streptococcus (catalpe -)
