Perjalanan Alamiah Penyakit

dr. Rohmania Setiarini

Understanding the characteristic natural history of a disease enables physicians to anticipate prognosis and to identify opportunities for prevention and control.

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“a type of internal state which is either an impairment of normal functional ability–that is, a reduction of one or more functional abilities below typical efficiency–or a limitation on functional ability caused by environmental agents” (C. Boorse, What is disease? In: Humber M, Almeder RF, eds. Biomedical ethics reviews. Humana Press, Totowa NJ, 1997, 7-8 (quoted in Temple et al., 2001)

what is disease?

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“a state that places individuals at increased risk of adverse consequences”

(Temple LKF et al., Defining disease in the genomics era. Science 3 Aug 2001;293:807-808)

what is disease?

The “natural history of disease” refers to the progression of disease process in an individual over time, in the absence of intervention.There are four stages in the natural history of a disease. These are:1. Stage of susceptibility2. Stage of pre-symptomatic (sub-clinical) disease3. Stage of clinical disease4. Stage of disability or death

Natural history of disease

The progress of a disease process in an individual overtime in the absence of intervention

Exposure host disease

recovery

disability

death

THE NATURAL HISTORY OF A DISEASE

STIMULUS to the HOST HOST REACTION RECOVERY

interrelation of Agent, Host and Environmental

factors

Latent Period (Pre-symptomatic)

Symptoms, Signs(Clinical)

with or without Defects, Disability

PREPATHOGENESIS PERIOD OF PATHOGENESIS

Health PromotionSpecific

Protection Early Diagnosis and Prompt Treatment, Disability Limitation

Rehabilitation

PRIMARY PREVENTION

SECONDARY PREVENTION TREATMENT TERTIARY PREVENTION

(Leavell's Level of Application of Preventive Medicine)

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• Induction – time to disease initiation

• Incubation – time to symptoms (infectious disease)

natural history

The time interval between contact with an agent and the first clinical evidence of resulting disease

Depends on :• Portal of entry (defense mechanism)• The ability of multiplication (infectivity) • Number of agents • Level of antibody in the host

It varies individually

INCUBATION PERIOD

Latent periodthe time interval from infection to development of infectiousness

Infectious periodthe time during which time the host can infect another susceptible host

Non-infectious periodthe period when the host’s ability to transmit disease to other hosts ceases

Incubation periodthe time interval between infection to development of clinical disease

Natural History Hepatitis A virus in children has low Pathogenicity and

low virulence, since many infected children remain asymptomatic and few develop severe illness.

In persons with good nutrition and health, measles virus has high Pathogenicity but low virulence, since almost all infected persons develop the characteristic rash illness but few develop the life-threatening presentations of measles, pneumonia, or encephalitis. In persons with poorer nutrition and health, measles is a more virulent disease, with mortality as high as 5-10%.

Finally, rabies virus is both highly pathogenic and virulent, since virtually 100% of all infected persons (who do not receive treatment) progress to clinical disease and death.

Agent with high infectivity and pathogenicity but low antigenicity will cause a relatively high disease prevalence in the community

Agent with high infectivity but low pathogenicity usually produce a mild or sub clinical symptom and carrier

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Natural history of coronary heart disease

“Spontaneous atherosclerosis” “Lipid lesion” Fibrointimal

lesionPlaque growth,

occlusion

Chronic minimal injury (blood flow, smoking) (youth?)

Accumulation of lipids and monocytes, toxic products, platelet adhesion(adolescence)

Migration & proliferation of smooth muscle cells

(adulthood)

Disruption

thrombi

(adulthood)

Chicken pox an infectious disease caused by the varicella-

zoster virus the latent period for chicken pox is shorter

than the incubation period, so a child with chicken pox becomes infectious to others before developing symptoms

Susceptiblehost

TIME

Incubation period

Death

Recovery

Exposure Onset

Latent Infectious Non-infectious

Infection

No infection

Clinical disease

HIV (AIDS) latent period relatively short infectious period occurs (many years) before the

onset of symptoms

Susceptiblehost

TIME

Incubation period

Death

Recovery

Exposure Onset

Latent Infectious

Infection

No infection

Clinical disease

Malaria caused by protozoan parasites of the genus

Plasmodium the stages of the parasite that are infective to

mosquitoes occur about 10 days after the development of symptoms

latent period is around 10 days longer than the incubation period, so early treatment of symptoms could have an important effect on transmission

Natural history of disease

Susceptiblehost

TIME

Incubation period

Death

Recovery

Exposure Onset

Latent

Infection

No infection

Clinical disease

Infectious