Disease Control: Natural History of Disease Flashcards
Natural History of disease
the course a disease takes from its onset i.e., exposure of the host to a causative agent, through its progression to the final outcome [recovery, disability or death], in the absence of treatment
List the essence of knowing the natural history of disease
- Every disease has its characteristic natural history
- The historical pathway may vary between individuals
- The characteristics of diseases are influenced by preventive
and therapeutic measures - An understanding the causal pathways of a disease and
knowledge of the natural history enables the care provider to
anticipate a prognosis and identify opportunities for
prevention and control e.g., type 2 diabetes or pneumonia
How many stages of the natural history of disease are present?
Four stages
List the stages of natural history(levels of prevention)
- Stage of susceptibility (seemingly good health)
Exposure to causal agents, etc. [Determinants] - Stage of subclinical disease (hidden and pathological changes
begin to occur)
Onset of symptoms of disease - Stage of clinical disease (disease manifests and this is the usual time of diagnosis)
- Stage of recovery, disability or death
What is another way (stages) to classify the natural history of disease?
– Stage of exposure [start of exposure]
– Stage of infection [onset of infection,
appearance of pre clinical and non
specific manifestations
– Stage of infectious disease [appearance of clinical manifestations]
– Stage of outcome [occurrence of outcome i.e., recovery, disability or death]
Another way to classify natural history (phases)
– Pre
pathogenesis phase [prior to exposure to determinants]
– Pathogenesis phase [post exposure with initiation of disease outcomes]
Give the updated stages and prevention levels
- Stage of susceptibility [primordial prevention]
- Stage of exposure [primary prevention]
- Stage of subclinical disease [secondary prevention]
- Stage of clinical disease [tertiary prevention]
- Stage of recovery [tertiary prevention]
Describe the stage of susceptibility
- Occurs in the pre
exposure period in the natural history of disease during which the
individual is vulnerable (or at risk) of acquiring an infection and or amenable to getting
exposed to and be harmed by
a health determinant - The host is in seemingly good
health - Determinants of ill
health might be
in the host’s immediate
environment - Host is
NOT exposed to the
determinants of ill health
Describe the stage of exposure
- Exposure of host to causal agent or determinants that are
sufficient to induce disease in host
– Malaria
plasmodium spp.
– Cholera
vibrio cholerae
– Lung cancer
tobacco smoke
Describe the stage of subclinical disease
- Incubation period [
infectious diseases ]/Latency period
chronic diseases
–the time of sub
clinical disease i.e., from time of exposure to the onset of
symptoms of disease
– Symptoms of the disease are usually not apparent
– Pathologic changes occur that can be detected by screening methods i.e.,
laboratory, radiological, etc.
– Period varies for each disease - Manifestations
non specific symptoms
Give the clinical effect and incubation period of organophosphate poisoning
Clinical effect - Nausea, vomiting, cramps, headache,
nervousness, blurred vision, chest pain,
confusion, twitching, convulsions
Latency period - Few minutes to few hours
Give the clinical effects and incubation periods of the following:
Salmonella
Varicella Zoster Virus
Salmonella - Diarrhoea, Fever, cramps. Usually 6 - 48 hours
VZV - Chicken pox. 10-21 days, usually 14-16 hours
Give the clinical effects and incubation periods of the following:
Treponema pallidum
Hep A
Hep B
Atomic bomb radiation
Treponema pallidum - Syphilis. 10-90 days, usually 3 weeks
Hep A - Hepatitis. 14-50 days, usually 4 weeks
Hep B - Hepatitis. 50 -180 days. Usually 2-3 months.
Atomic bomb radiation - Leukemia. 2-12 years
Give the clinical effects and incubation periods of the following:
Treponema pallidum
Hep A
Hep B
Atomic bomb radiation
Treponema pallidum - Syphilis. 10-90 days, usually 3 weeks
Hep A - Hepatitis. 14-50 days, usually 4 weeks
Hep B - Hepatitis. 50 -180 days. Usually 2-3 months.
Atomic bomb radiation - Leukemia. 2-12 years
How do diseases typically show clinical manifestation?
- Some cases do not progress to clinical disease
- Others are mild, moderate, severe or fatal
