Principles of infectious diseases and epidemiology Flashcards
Human genome project
(set out to map all the microorganisms in the body)
Symbiosis
Interactions bw different species within a community
At least one is dependent upon the other
Commensalism
One population benefitted, the other is not affected
Ciliary escalator
Cilia in nsal cavity and resp tract tht moves trapped bacteria towards the outside
E.coli: Mutualism:
Produce usuefyl vitamins, and outcompete pathogens and hosts provide E.cole with nutrients
Microbial antagonism
Competition bw microbes
Opportunistic pathogens:
Normal microbiota that can be pathogenistic under certain circumstances
I.e E.coli, staphylococcus
Koch Postulates
Establishing causal relationship bw pathogen and infectious disease
Same pathogen is present in every case of disease
Pathogen must be isolated from diseased host and grown in pure culture
Pathogen from pure culture must cause disease in healthy lab animal
Pathofen must be isolated from inoculated animal and shown to be the original pathogen
Exceptions to Koch’s postulates
Some disease can be caused by multiple pathogens
I.e pneumonia
Dysbiosis disease - Diseases caused by disturbance of normal flora
I.e. Yeast infection (When lactobacillus are low, yeast organism conc. increase)
One organism ca ncause several disease conditions
I.e. Scarlet fever is the same organism that causes the flesh eating disease, Streptococcus pyogenes
Same agents are not culturalble in the lab
Some pathogens only cause disease in humans
Role of epidemiology
to learn how to treat and prevent the spread of disease
Epidemic vs pandemic
Significant more than usual occurrence of a disease in an area (continent)
Pandemic is a significant over occurrence of a given disease on multiple continents at once
Most common type of nosocomial infection
UTI
Passive transfer of a vector of disease
The spread of disease by a fly walking over food
Classifying infectious. disease
Acute infection: Immediate affect, no long term effect
Acute infection (late compilcation): Immediate affect, long term effect later on
Latent infection: Immediate affect, later recurrence (acute)
Chronic infection: Once effected, continous level of infection
Chronic infection (late comlication): ONce effected, continues constant until infection hits crisis point
Slow infection: No accute stage until right at the end (prions)
Systemic infection
Affecting multiple organs and spread via blood and or lymph (shock infections, fungal infections)
Focal infection
Agent travels through blood or lymph, cause disease, one site/organ (infectious endocarditis after oral surgery
Subclinical disease
No noticeale signs or sypmtoms (Potential carriers of the disease
I.e. H.pylori, germs on hands, staphaureus)
Bacteremia
Bacteria in the blood
Viremia
Viruses in the blood
Toxemia
Toxins in the blood
Speticemia
Multiplication of pathogen in blood (Blood poisoning), can lead to sepsis (gneerlizaed inflammation of the blood vesesl
5 Stages of disease
Incubation: Before and signs or symptoms (Very few microbes)
Prodromal: Early mild symptoms of disease
Illness: Most sever disease signs/sypmtoms
Decline: Fewer signs /symptoms
Concalescence: Patient regains strength (Body returns to predeceased state)
At which stage in the disease are you contagious
any
Reservoirs of infection
Allow pathogens to survive, replicate and transmit to others
Human - human infectious disease depend oup on human reservoirs
Humans
Animals: diseases transmitted from animals to humans are called zoonoses
Non-living - soil , water, food etc.
5 forms pf disease transmission
direct contact
indirect contact
droplet transmission
vehicle transmission
Vector transmission (insects)
Direct contact
(horizontal - physical contact; vertical, mother to fetus/newborn)
Indirect contact
(Fomites - inanimate object that facilitae spread of a pathogen)
Droplet transmission:
Short range droplet nuclei
Vehicle transmission
Foodborne
Waterborne
Airborne: Small droplets that remain airborne for extended periods of time (aerosolized) can travel more than 1 m from host
Vector transmission (insects)
Mechanical: Passive transport of pathogen
Biological: BIting/feeding on the host
WHy should we expect increased incidents of emerging infectious diseases?
Increased population: Increasing habitat, therefore encountering new pathogens
Travel means microorganisms can travel
Climate change: Mosquitoes tend to carry diseases in tropical areas, but with increased temperature, pathogens can survive in larger areas
Grwoing immunocompromised population
Decreased herd immunity (majority vaccination protects those who are not)
Antibiotic resistant organisms
Nosocomial infections
HAI
Epidemiology
Study of the causes, distribution and control of disease in human populaitons
What does epidemiology attempt. to determine
Causitive agent
Source/reservoir of agent
Mechanism of transmission
Host and environmental factors that facilitate development of disease
Best control measures
Communicable disease
Diseases that can spread from one host to another
Contagious diseaes
Diseasess that EASILY spread from one host to another
Noncommunicable disease
Disease that are not transmitted from one host to anther
Botulism and tetanus: BC they’re caused by toxins in the bacteria, NOT the bacteria itself
Descriptive epidimeiology (restrospective study)
Collection and analysis of data caoncerning disease (i.e. individuals affected, place, period etc.)
John Snow
Analytical (case control study)
Comparison of diseased group and healthy group to determine its probable cause
Florence Nightingale
Experimental (cohort study, randomized control study)
Begin with a hypothesis and use controlled experiments to test the hypothesis with a group of people
Ignaz Semiwels: Mothers giving birth by help of physicians would die more often than those being helped by midwives
Many mothers died from infections spread by docters lack of cleanliness
Epidemic
Outbreaks that affect an entire region in a country or group of countries
Pandemic
Outbreak on global scale
Endemic
Disease that normally occurs in a particular geographic area (among particular population)
When disease comes under control, certain number of people in population ALWAYS affected (even if it is a small number of individuals, it can never be completely eradicated)
*400 new AIDS cases in 2004 (_______) compared to 9000 total cases living with AIDS in 2004 (________)
Incidence
Prevalence
Why investigate disease outbreaks
Prevent additonal cases
Prevent future outbreaks
Increase our understanding of the disease
Eva,uate prevention strategies
Legal, finanial and ethical responsibilibies
Public reassurance
Reduce socio-economic impacts
Incidence
Fraction of population that ocntracts a disease during a specific time
Prevalence
Fraction of population having a specific disease at a given time (regardless of when it first appeared; include old and new cases)
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