Principles of Disease and Epidemiology
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Transcript of Principles of Disease and Epidemiology
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
M I C R O B I O L O G Ya n i n t r o d u c t i o n
ninth edition TORTORA FUNKE CASE
14Principles of Disease and
Epidemiology
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Principles of Disease and Epidemiology
Pathology : The study of disease
Etiology: The study of the cause of a disease
Pathogenesis: The development of disease
Infection: Colonization of the body by pathogens
Disease: An abnormal state in which the body is not
functioning normally
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Infection and Disease
ETIOLOGY –cause of
disease
PATHOGENISIS-how the
disease develops
The Adventures ofSherlock Holmes,20th Century Fox-1939Basil RathboneNigel Bruce
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Infection and Disease
Infection and disease
represents a balance.
A pathogen causes harm
A commensal can be part of
the normal flora
The site in the body can
determine the classification –
E. coli in urine=bad; E. coli in
colon = normal
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Normal Microbiota and the Host
Locations of normal
microbiota on and in
the human body.
Table 14.1c
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NORMAL MICROBIOTA
You can contain 1013 cells
You also contain 1014 cells that are bacterial
These make up normal and transient flora
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Normal Microbiota and the Host
Transient microbiota may be
present for days, weeks, or
months.
Normal microbiota permanently
colonize the host.
Symbiosis is the relationship
between normal microbiota and
the host.
Figure 14.1c
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Normal Microbiota and the Host
Microbial antagonism is a competition between
microbes.
Normal microbiota protect the host by:
Occupying niches that pathogens might occupy
Producing acids
Producing bacteriocins
Probiotics are live microbes applied to or ingested into
the body, intended to exert a beneficial effect.
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MICROBIAL COOPERATION MICROBES
PERIODONTAL DISEASE
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OPPORTUNISTIC MICROBES
A good organism which gains
entrance into a new site can be
pathogenic
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Koch’s Postulates
Koch's postulates are
used to prove the
cause of an infectious
disease.
Figure 14.3 (2 of 2)
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Koch’s Postulates
Koch's postulates are
used to prove the
cause of an infectious
disease.
Figure 14.3 (1 of 2)
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Symbiosis
In commensalism, one organism is benefited and the
other is unaffected.
In mutualism, both organisms benefit.
In parasitism, one organism is benefited at the expense
of the other.
Some normal microbiota are opportunistic pathogens.
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Classifying Infectious Diseases
Symptom: A change in body function that is felt by a
patient as a result of disease.
Sign: A change in a body that can be measured or
observed as a result of disease.
Syndrome: A specific group of signs and symptoms
that accompany a disease.
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Classifying Infectious Diseases
Communicable disease: A disease that is spread from
one host to another.
Contagious disease: A disease that is easily spread
from one host to another.
Noncommunicable disease: A disease that is not
transmitted from one host to another.
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Occurrence of Disease
Incidence: Fraction of a population that contracts a disease
during a specific time.
Prevalence: Fraction of a population having a specific disease at
a given time.
Sporadic disease: Disease that occurs occasionally in a
population.
Endemic disease: Disease constantly present in a population.
Epidemic disease: Disease acquired by many hosts in a given
area in a short time.
Pandemic disease: Worldwide epidemic.
Herd immunity: Immunity in most of a population.
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Severity or Duration of a Disease
Acute disease: Symptoms develop rapidly.
Chronic disease: Disease develops slowly.
Subacute disease: Symptoms between acute and
chronic.
Latent disease: Disease with a period of no symptoms
when the patient is inactive.
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Extent of Host Involvement
Local infection: Pathogens are limited to a small area
of the body.
Systemic infection: An infection throughout the body.
Focal infection: Systemic infection that began as a
local infection.
Bacteremia: Bacteria in the blood.
Septicemia: Growth of bacteria in the blood.
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Extent of Host Involvement
Toxemia: Toxins in the blood.
Viremia: Viruses in the blood.
Primary infection: Acute infection that causes the
initial illness.
Secondary infection: Opportunistic infection after a
primary (predisposing) infection.
Subclinical disease: No noticeable signs or symptoms
(inapparent infection).
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Predisposing Factors
Make the body more susceptible to disease
Short urethra in females
Inherited traits such as the sickle-cell gene
Climate and weather
Fatigue
Age
Lifestyle
Chemotherapy
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The Stages of a Disease
Figure 14.5
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Reservoirs of Infection
Reservoirs of infection are continual sources
of infection.
Human — AIDS, gonorrhea
Carriers may have inapparent infections
or latent diseases.
Animal — Rabies, Lyme disease
Some zoonoses may be transmitted to humans.
Nonliving — Botulism, tetanus
Soil
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Transmission of Disease
Contact
Direct: Requires close association between infected
and susceptible host.
Indirect: Spread by fomites.
Droplet : Transmission via airborne droplets.
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Transmission of Disease
Figure 14.6a, d
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Transmission of Disease
Vehicle: Transmission by an inanimate reservoir
(food, water).
Vectors: Arthropods, especially fleas, ticks, and
mosquitoes.
Mechanical: Arthropod carries pathogen on feet .
Biological: Pathogen reproduces in vector.
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Transmission of Disease
Figures 14.7b, 14.8
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Nosocomial (Hospital-Acquired) Infections
Are acquired as a result of a hospital stay.
5-15% of all hospital patients acquire nosocomial
infections.
Figures 14.6b, 14.9
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Relative Frequency of Nosocomial Infections
Table 14.5
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Percentage of Nosocomial Infections
Percentage Resistant to Antibiotics
Gram + cocci 51% 29%-89%
Gram – rods 30% 3-32%
Clostridium difficile 13%
Fungi 6%
Common Causes of Nosocomial Infections
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NOSOCOMIAL INFECTIONS
In the United States, it has
been estimated that as
many as one hospital
patient in ten acquires a
nosocomial infection, or 2
million patients a year.
Estimates of the annual cost
range from $4.5 billion to
$11 billion and up.
Nosocomial infections
contributed to 88,000
deaths in the U.S. in 1995.
One third of nosocomial
infections are considered
preventable.
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Emerging Infectious Diseases
Diseases that are new, increasing in incidence, or
showing a potential to increase in the near future.
Contributing factors
Genetic recombination
E. coli 0157, Avian influenza (H5N1)
Evolution of new strains
V. cholerae 0139
Inapproriate use of antibiotics and pesticides
Antibiotic resistant strains
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Emerging Infectious Diseases
Changes in weather patterns
Hantavirus
Modern Transportation
West Nile virus
Ecological disaster, war, and expanding human settlement
Coccidioidomycosis
Animal control measures
Lyme disease
Public Health failure
Diphtheria
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Crossing the Species Barrier
UN 13.3
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Epidemiology
The study of where
and when diseases
occur
Figure 14.10
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John Snow 1848-1849 Mapped the occurrence of cholera in London
Ignaz Semmelweis 1846-1848 Showed that hand washing decreased the incidence of puerperal fever
Florence Nightingale 1858 Showed that improved sanitation decreased the incidence of epidemic typhus
Epidemiology
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Descriptive Collection and analysis of data regarding occurrence of disease
Snow
Analytical Comparison of a diseased group and a healthy group
Nightingale
Experimental Study of a disease using controlled experiments
Semmelweis
Case reporting Health care workers report specified disease to local, state, and national offices
Nationally notifiable diseases
Physicians are required to report occurrence
PLAY Animation: Epidemiology
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.7 (1 of 2)
“AIDS” to “Gonorrhea”; “Pertussis” to “Streptococcal Toxic Shock Syndrome”
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“Haemophilus influenzae” to “Mumps”; “Streptococcus pneumonaie” to “Yellow Fever”
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Centers for Disease Control and Prevention (CDC)
Morbidity: Incidence of a specific notifiable disease.
Mortality: Deaths from notifiable diseases.
Morbidity rate: Number of people affected in relation to
the total population in a given time period.
Mortality rate: Number of deaths from a disease in
relation to the population in a given time.
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Collects and analyzes epidemiological information in
the United States.
Publishes Morbidity and Mortality Weekly Report
(MMWR) www.cdc.gov
Centers for Disease Control and Prevention (CDC)
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TERMINOLOGY REVIEW
Sign
Symptom
Syndrome
Communicable
Contagious
Non-communicable
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TERMINOLOGY REVIEW
Local
Systemic
Focal
Sepsis
Septicemia – bacteremia, viremia, toxemia
Primary, Secondary, Subclinical
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TERMINOLOGY REVIEW
Incidence
Prevalence
Sporadic
Endemic
Epidemic
Pandemic
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TERMINOLOGY REVIEW
What was the incidence of Aids in 2005?
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TERMINOLOGY REVIEW
Acute
Subacute
Chronic
Latent
Herd Immunity
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Now We Have Disease!
Predisposing factors
Resistance
Incubation Period
Prodromal Period
Period of Disease
Period of Decline
Convalescence
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SOURCES OF DISEASE
Human reservoirs
Animal reservoirs
Zoonotic Diseases
Nonliving reservoirs (food &
water)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
MOVE IT ON!
DIRECT CONTACT
INDIRECT CONTACT
DROPLET
VEHICLE