3. Definition
The natural history of disease is the course a disease
takes in individual people from its pathological onset
("inception") until its resolution (either through
complete recovery or eventual death).
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4. Introduction
• The natural history of a disease is sometimes
said to start at the moment of exposure to
causal agents.
• Knowledge of the natural history of disease
ranks alongside causal understanding in
importance for disease prevention and control.
• Natural history of disease is one of the major
elements of descriptive epidemiology.
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6. Phases Of Diseases
Pre-pathogenic period
• In the pre-pathogenic period, the disease
originates, but the patient doesn't yet
present clinical symptoms or changes in
his/her cells, tissues, or organs.
• This phase is defined by the host conditions,
the disease agent (such as microorganisms
and pathogens), and the environment.
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7. Phases Of Diseases
Pathogenic period
• The pathogenic period is the phase in
which there are changes in the patient's
cells, tissues, or organs, but the patient
still doesn't notice any symptoms or signs
of disease.
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8. Phases Of Diseases
Incubation period vs. latency period
• In transmissible diseases (like the flu), we
refer to this phase as the incubation period
because it's the time in which
microorganisms are multiplying and
producing toxins. It's fast-evolving and can
last hours to days.
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9. Phases Of Diseases
Clinical period
• The clinical period is when the patient finally
presents clinical signs and symptoms. That is:
when the disease is clinically expressed and the
affected seek health care.
• During this phase, if the pathological process
keeps evolving spontaneously without medical
intervention, it will end in one of three ways:
recovery, disability, or death.
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10. Prevention of Diseases
Primary prevention
• Primary prevention is a group of sanitary
activities that are carried out by the
community, government, and healthcare
personnel before a particular disease
appears. This includes:
• Promotion of health
• Protection of health
• Chemical Treatment
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11. Prevention of Diseases
Secondary prevention
• Secondary prevention, also called premature
diagnosis or premature screening, is an early
detection program.
• More specifically, it's an epidemiological
program of universal application that is used to
detect serious illnesses in particular,
asymptomatic populations during the pre-
pathogenic period.
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12. Prevention of Diseases
Tertiary prevention
• Tertiary prevention is the patient's recovery
once the disease has appeared. A treatment
is administered in an attempt to cure or
palliate the disease or some of its specific
symptoms.
• The recovery and treatment of the patient is
carried out both in primary care and in
hospital care.
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13. Prevention of Diseases
Quaternary prevention
• Quaternary prevention is the group of
sanitary activities that mitigates or entirely
bypasses the consequences of the health
system's unnecessary or excessive
interventions.
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14. Conclusion
Natural history of disease refers to the
progression of a disease process in an individual
over time, in the absence of treatment.
For example, untreated infection with HIV causes
a spectrum of clinical problems beginning at the
time of seroconversion (primary HIV) and
terminating with AIDS and usually death.
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