Principles of Disease and Epidemiology

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Chapter 14

• Principles of Disease and Epidemiology

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Terminology

• Pathology
• Disease
• Infection
• Normal flora
• Transient flora
• Microbial antagonism
• Competitive exclusion

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Relationship between microbe and host

• Symbiosis
• Mutualism
• Commensalism
• Parasitism
• Opportunistic pathogens

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Etiology of infectious disease

• Kochs postulates

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Etiology of infectious disease

• Kochs postulates
• Exceptions to Kochs postulates
• Unique culture requirements
• Unique signs and symptoms of a disease
• Several organisms can cause the same disease
• One organism can cause several diseases
• Humans are the only host for some pathogens

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Classifying infectious diseases

• Symptoms
• Signs
• Syndrome
• Communicable disease
• Contagious disease
• Noncommunicable disease

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Occurrence of a disease

• Incidence
• Prevalence
• Sporadic
• Endemic
• Epidemic
• Pandemic

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Severity or duration of a disease

• Acute
• Chronic
• Subacute
• Latent
• Group immunity

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Extent of host involvement

• Local infection
• Focal infection
• Systemic infection
• Bacteremia
• Septicemia
• Toxemia
• Viremia

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Extent of host involvement . . .

• Primary infection
• Secondary infection
• Subclinical or inapparent infection
• Carrier

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Patterns of disease

• Predisposing factors
• Development of a disease
• Incubation period
• Prodromal period
• Period of illness
• Period of decline
• Convalescence

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Spread of infection

• Reservoirs of infection
• Human reservoirs
• Animal reservoirs
• Nonliving reservoirs

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Transmission of disease

• Contact transmission
• Direct
• Indirect
• Fomite
• Droplet transmission

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Transmission of disease

• Contact transmission
• Vehicle transmission
• Food
• Water
• Air

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Transmission of disease

• Contact transmission
• Vehicle transmission
• Vectors
• Mechanical
• Biological

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Nosocomial infections

• Microorganisms in the hospital
• Compromised host
• Chain of transmission

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Control of nosocomial infections

• Frequent hand washing
• Isolation
• Education
• Avoid overuse of antibiotics

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Emerging infectious diseases

• Mutations
• Global changes
• Frequent travel
• Ecological changes
• Failure of public health policies

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Epidemiology

• Descriptive
• Analytical
• Experimental

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Case reporting

• Centers for Disease Control and Prevention
• MMWR
• Notifiable diseases
• Morbidity rate
• Mortality rate
• World Health Organization (WHO)