Epidemiology. Epidemiology involves: –determining etiology of infectious disease –reservoirs of...
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Transcript of Epidemiology. Epidemiology involves: –determining etiology of infectious disease –reservoirs of...
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Epidemiology
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• Epidemiology involves:– determining etiology of infectious disease– reservoirs of disease– disease transmission – identifying patterns associated with outbreaks – outlining diagnostic tools and treatment options
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– Incidence
– Prevalence
– Endemic
– Epidemic
– Pandemic
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• In order for disease to spread:– Pathogen must have reservoir– Pathogen must be transmitted to susceptible
host
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• Reservoirs of infectious disease:– Humans– Non-human animals– Environmental (non-living)
• Recognizing reservoir can help protect population from disease
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• Human reservoirs– Infected humans most significant reservoirs
• If only reservoir disease is easier to control• Symptomatic or Asymptomatic carriers
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• Non-human animal reservoirs– Zoonotic transmission
(zoonoses) • Disease typically more
severe in humans• Often accidental and
may be a dead end for pathogen
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• Environmental reservoirs– 2 most important are
• Water• Soil
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• Transmission– Successful pathogen must be passed from
reservoir to next susceptible host• Contact• Vehicle• Vector
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• Contact– Direct contact
• Occurs when one person physically touches another• Hands are the main source
– Indirect contact• Transmission via inanimate objects or fomites
– Clothing, tissues, doorknobs and drinking classes– Droplet transmission
• Respiratory droplets within three feet of release
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• vehicle transmission– Food, water and air
• Food contamination may originate with animal or occur during food preparation
• Waterborne disease can involve large numbers of people; prevention involves proper sanitation
• Respiratory droplets dry; creates droplet nuclei that may remain suspended or become re-suspended
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• Vectors– Any living organism that can
carry a pathogen• Most common are arthropods• Mechanical or biological
– Control of vector-borne disease directed at controlling arthropod population
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• Many disease occur in cycles– May be annual or occur over decades
• Flu• plague
• Herd immunity is an important factor in cycles– Low levels could lead to reemergence of
disease• Small pox
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• Reduction and eradication of disease– Some success
– Efforts directed at:• Improving sanitation• Reservoir and vector control• Vaccination• Chemotherapy
– Why aren’t all infectious diseases eradicated?
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• Four mechanisms public health agencies use to control disease transmission:
1. Isolation
2. Quarantine
3. Immunization
4. Vector control
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Infectious Disease Surveillance
• National disease surveillance network– Network of agencies across the country
• monitor disease development– Agencies include
• Public Health Departments• Centers for Disease Control and Prevention (CDC)
– Notifiable Diseases
• World Health Organization (WHO)
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Nosocomial Infections• Hospital acquired
infections– Range from mild to fatal
• Increased 36% in the last 20 years
– Leading cause of death in the US
• 100,000 deaths per year
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• Reservoirs of nosocomial pathogens:– Exogenous
• Other patients• Hospital environment• Health care workers
– Endogenous• Patient’s own normal flora