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Epidemiology

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the study of when& wherediseases are transmitted in populations

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etiology

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cause of a disease

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pathogenesis

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the manner in which a disease progress

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infection

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invasion or colonization of the body by microorganisms

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disease

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any change from a state of health

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normal flora vs transient flora

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normal flora-microbes that are resident in a region of the body
transient flora-appear briefly in a body region then disappear.

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communicable disease

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a disease that can be passed from one host to another

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noncommunicable disease

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cannot be spread from one host to another

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contact transmission

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direct(person-person)
influenza
indirect(nonliving object)
A)fomite-tissues,towels
B)comtaminated syringes serve as fomites in transmission of AIDS
Droplet(mucous droplets from sneezing)
Influenza, pneumonia,pertusis
spread by droplets

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vehicle transmission:by medium
A)air
B)food
C)air

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vectors:anthropds carry pathogens.
Biological transmission-
insect bite
mechanical transmission-
from contact with insect

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predisposing factors for disease
1)gender
2)age
3)fatigue
4)nutrition

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nosicomial infections
A)caused by opportunist pathogens in compromised host
(resistance to infection impaired by disease, therapy or disease)
b. transmitted by by airborne and contact
c. reserviors are hospital staff, visitors and other staff

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endemic-disease constantly present in population-common cold
epidemic-disease acquired by many people in a population in a short time(INFLUENZA)

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epidemology-the studt of when&
where diseases occur & how they are transmitted in populations
CDC-isues the morbidity& mortality weekly report that contains information on morbidity & mortality for notifiable diseases

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1)incubation period
initial infection&appearance of S/S
2)prodormal period-mild symptoms immediately following incubation period
3)period of illness-
acute illness phase,overt s/s
if pt not overcome, may die
4)period of decline-
s/s subside
5)period of convalescence-revovery
return to nondiseased state

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reservior of infection
1)human-carrier
AIDS,DIPTHERIA, hapatitis, gonnerehea
2)animal-rabies,malaria, anthrax
3)nonliving(soil and water)
Clostridium species deposited by animal waste in soil
contaminated waste
-Salmonella typhi, Vibrio cholerea

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pathogenicity-ability to cause disease
virulence-the degree of pathogenicity.
The pathogen must enter the host's body.
1)mucous membrabes
2)skin
3)parenteral route

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LD-50 measure of virulence, lethal dose in which the pathogen will kill half of the test animals.
ID-50 If pathogen causes only a nonfatal disease(infectous disease). The fewer the microorganisms required, the higher the virulence.

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adhesions=proteins,molecules on the surface of microorganisms that binds to hosts cells. Ligands(proteins on surface of bacteria(adhesions) and viruses(attachment proteins)
Found on fimbrae, flagella and glycocalyces

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methods by which microbes invade host tissues.
1)evade (impairs) pagocytosis-Streptococcus pneumoniae with a capsule are virulent(those without a capsule are not due to phagocytosis). Some pathogens
produce capsules:Bacillus anthrax
MYCOLIC ACID: waxes of cell
wall of MYCOBACTERIUM turberculosis resist phagocytosis. Can also multiply inside phagocytes

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Exoenzymes
1)Coagulase-coagulate blood
ex:S.aeurus
2)kinases-break down fibrin& dissolve clots. Isolate infection. EX: Streptococcus pyogenes & Staphylcoccus aureus
3)Hyaluronide-polysaccaride. Make space so pathogens go deep in the tissues. Unglues cell-cell connection in connective tissue. Ex: Streptococcus, Clostridium
4)Collagenase-breaks down collagen,helps spread gas gangrene. EX:Clostridium in necrotic tissue

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Toxins:poisons made by some microbes
1)exotoxin-G+, some-
proteins. By-product of metabolism of living cell.Released outside cell.Highly specific. Most lethal.
Endotoxin-G-. Lipopolysaccharides(lipid A
of gram-negative outer membrane). rELEASED UPON DEATH AND LYSIS of the bacteria, as well during bacterial multiplication.