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29 Cards in this Set
- Front
- Back
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prevalence- definition, rate and example
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-total number of cases of a disease in a population at a specific time
- total # of cases/ total in group -prevalence of diarrhea(disease) in a camp(group) was 33%(prevalence) |
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incidence- definition, rate and example
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-rate of disease development in a given group over a period of time.
- # of persons developing a disease x unit time = incidence rate -incidence of chicken pox was 10% a day in a grade 2 class |
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period prevalence rate- definition, rate
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-all the diseases affecting a group during a time period.
-# of people with a disease over a time period / total number in group OR period at beginning + annual incidence during -In 1990, etc |
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Morbidity rate
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-incidence of disease in a population- both fatal and non fatal cases.
-ex) in 2000, etc etc |
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Disease progression steps
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1.infection- pathogen invades host and starts multiplying
2. Incubation- time between infection and symptoms 3. Acute period- the disease is at its height (overt symptoms) 4. Decline period- symptoms are subsiding 5. Convalescent period- patient begins to regain strength and returns to normal |
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Mortality rate- definition, equation, and example
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-incidence of death in a population
-mortality rate= # of persons dying x unit time / total number in group -in percentage or # deaths/ say 10000 |
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Endemic- definition and example
Epidemic- definition and example Pandemic- definition and example |
1. endemic- present at all times in relatively low numbers. very hard to eliminate
ex) malaria, polio virus 2.Epidemic- more cases occur than expected in a certain community or region. ex) HIV/AIDS - US in 1992 3. Pandemic- very widespread epidemic which affects region, continent or world. ex) Plague 1300, Spanish flu 1918, AIDS 1981-2005. |
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the four causes of infectious diseases
- what causes AIDS, TB, Malaria, ARI, Diarrhea |
1. bacteria- unicellular organisms which has no nucleus
2. protozoa- unicellular organisms which has a nucleus 3. Virus- intracellular parasite that cannot reproduce by itself 4. Prions -proteins that cause slow degenerative disease in humans and animals -NO KNOWN ARCHAEA CAUSED DISEASES 1.aids- virus, TB- bacteria, Malaria- protozoa, ARI- fungus, bacteria, virus, diarrhea- virus, bacteria |
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infectious diseases as a cause of death in Africa, and the Americas
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- In Africa, infections account for 61% of deaths
-In the Americans, it accounts for 11% of deaths- cardiovascular, followed by cancer, is the leading cause |
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BACTERIA: gram positive and gram negative
1. gram positive- definition and example 2.gram negative- definition other classification of eubacteria |
- the test classifies bacteria based on cell structure
1. gram positive- gets stained blue or violet because of the thick peptidoglycan in cell wall. EX) TB, diptheriae 2. gram negative- doesn't stain blue or violet, but it does stain red or pink due to the counter stain. -ribosomal SSU classification |
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PROTOZOA (EUKARYA)
- example of parasite and disease -classified based on... |
- plasmodiums vivax
ex. malaria -18S ribosomal subunit |
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Baltimore's viral classification
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- puts viruses in 1 of 7 groups
-based on sense, method of rep, ds or ss, and combos of DNA or RNA |
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Koch's postulates
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-the 4 criteria to establish relationship between disease and microbe
1. The pathogen must be present in all organisms suffering from the disease 2. The pathogen must be isolated and grown in pure culture 3. The pathogen should cause the disease in a healthy organism 4. The pathogen must be re-isolated and shown to be the same as original |
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disease reservoirs
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- a site where the infectious agent resides alive and infects organisms
-can be inanimate- ex) soil and botulism -can be animate- ex) humans and whooping cough |
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Carriers
-2 kinds: acute and chronic |
-infected individuals sans symptoms. they can infect other people (human reservoirs).
-acute carrier- individuals in the incubation period who are only temporary carriers(until they recover). ex chicken pox -chronic carriers- individuals who remain infected even after they have recovered from the clinical disease. ex) typhoid mary |
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zoonosis - definition, problem, how to control, examples
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-disease that primarily occurs in animals but is transmitted to humans
-problem- health measures for animals are less developed than humans- infection rates higher in animal and difficult to control -the only way to control is to eliminate the disease reservoir. examples: bovine TB(cattle to human), plague (rats to humans), malaria ( mosquitos to humans), nipah virus( bats to pigs to humans) |
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Common source Vs. host to host epidemics
-graph trends |
common source- source epidemic from the infection of a large number of people from a common source- such as food or water
example) E.coli- drinking water reservoirs were contaminated by cattle feces host-to-host epidemics- can be initiated by the introduction of one infected individual infecting others in the population. examples) TB, influenza, HIV -common source- rapid increase in incidences followed by a rapid decline -host to host- slow, progressive increase in disease incidences followed by a gradual decline. |
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Transmission
-how to follow transmission -types of transmission (5) |
- must correlate geographical, seasonal, and age group incidence of a disease
1. person to person - airbourne (droplets), direct contact, sexually transmitted, body fluids, 2. animal to person: mammal-transmitted: rabies, arthropod-transmitted: malaria 3.soilbourne: pathogen in soil 4.waterbourne: pathogen in drinking water 5.medical devices |
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HIV/AIDS transmission
men vs women Hospital acquired (nosocomial) infections trends |
men- largest cause is homosexual contact
women- heterosexual contact -pneumonia then urinary tract then bloodstream |
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Host/pathogen relationship
1.evolutionary processes they are subject to (4) |
1. mutations in DNA or RNA of host or pathogen
2. vertical inheritance of these mutations 3. lateral gene transfer (transposons) 4. natural selection of mutated individuals |
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Mutation rates
- about -virus vs. bacteria |
- they vary- rates are higher in viruses than bacteria and protozoa
Why? In bacteria, DNA replication is constrained by mechanisms to correct mutations; however there is a threshold to the energy spent on corrections in viruses, DNA replication/ RNA synthesis is not constrained by these mechanisms |
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Molecular determinants of virulence
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virulence is determined by the combo of molecules succumbing to virus, bacteria, or protozoa, and the ability to invade the host while avoiding host barriers.
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Host susceptibility to infection
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-mutations in host gene involved with resistance may lead to increased susceptibility to infection by a given pathogen
ex) individuals with: c substitution at INT4 (intron 4), etc have a higher risk of TB |
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Control of disease
2 means of doing this |
1. controls directed against the reserviors
2. controls directed against transmission of the pathogen: immunization, quarantine, surveillance, and pathogen eradication |
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1. Controls against reservoirs
-if its a domestic animal, wild animal, insect, human |
1. if its a domestic animal, human infection can be prevented if the disease is eliminated from animal population by: immunization, destruction of infected animal (mad cow, bovine TB)
2. If its a wild animal, eradication or immunization is difficult. Efficiency of oral rabies is untested 3. If its an insect, elimination can be achieved with chemicals or other lethal agents. (DTT for yellow fever and malaria) 4. If its humans, control and eradication is difficult- especially with asymptomatic carriers |
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2. Controls against transmission of pathogens
-pathogen eradication, immunization, quarantine, and surveillance |
Pathogens via food and water can be eliminated by destroying pathogens in the vehicle- water purification, pasteurization of milk
1.pathogen eradication- successful in smallpox via- thorough vaccinations, and quarantine of the infected and vaccinate all contacts by WHO. -unsuccessful in poliovirus: plan to eradicate by 2003. problems, in nigeria they believe that immunization is linked to women infertility. 2. Immunization- the percentage of immunization varies with the virulence of the pathogen and condition of the population. ex) measles -usually children are adequately immunized; however adults are often not sufficiently immunized because immunization wears off. 3.quarantine- restricting infected individual to prevent transmission. diseases that are quarantineable: small pox, yellow fever, cholera, plague, typhoid fever, relapsing fever |
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Surveillance
- health Canada's surveillance list describes most infectious diseases since 1924 |
chlamydia, chicken pox
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Emerging and Re-emerging disease- defined
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emerging- disease that has suddenly become prevalent
ex) influenza, AIDS reemerging- disease thought to be controlled but because of its resistance, the disease has reemerged. ex) TB, malaria, rabies |
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Factors of influencing emergence of disease (5)
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1.environmental change (climate, deforestation)
2. human behaviour (sexual promiscuity) 3. international travel and commercial 4. technical failings and public health breakdowns 5.microbial adaptations |
