Acute and chronic disease · Biology Class 9–10 | StemPy Lab
Course 10.1·Lesson 2 of 3
Acute and chronic disease
A disease is a failure of some part of the body to work well. It shows itself in symptoms and signs. An acute disease lasts a short time, like a common cold. A chronic disease lasts a long time, even for life, like tuberculosis or elephantiasis, and harms health much more.
about 30 min1 simulation1 practice question1 Python program6 questions to check yourself
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What is a disease?
The word disease comes from "dis-ease": a lack of ease, or comfort. When a disease affects a person, some part of the body or the mind does not work as it should.
A cold makes the nose blocked and the throat sore.
A cut that gets infected fills with pus and hurts.
A stomach illness gives loose motions and pain.
Each disease affects particular parts of the body. A lung disease harms the lungs, and a stomach disease harms the gut. But when one part fails, the whole person feels unwell. So a disease affects overall health too.
Symptoms and signs
How do we know that a person has a disease?
Symptoms are what the patient feels or notices: a headache, a cough, pain, loose motions, a wound that will not heal.
Signs are what the doctor finds by examining the patient or by tests: a high temperature, an unusual sound in the chest, a changed blood count.
Symptoms and signs point to a disease, but one symptom can have many causes. A cough can come from a cold, from a dust allergy, or from a lung disease. So a doctor often uses tests, and not only the symptoms, to find the disease.
Acute disease
Some diseases last only for a short time. They are acute diseases. A common cold is the usual example. A person gets a blocked nose and a sore throat, feels unwell for about a week, and then recovers.
Acute diseases usually do not harm overall health very much. The body soon recovers, and the person goes back to school or work. Do not think that acute means mild, though. It only tells us that the disease is short. Some acute diseases can be serious while they last.
Chronic disease
Other diseases last for a long time, for many months or years, and sometimes for a whole life. These are chronic diseases.
Tuberculosis (TB) of the lungs is a chronic disease. A patient has a cough for weeks, loses weight and feels weak. A full course of treatment lasts about six months.
Elephantiasis is a chronic disease in which the legs or other parts swell for many years.
Two graphs side by side. The left graph, for an acute disease such as a common cold, shows how unwell a person feels over ten days. The curve rises to a peak near day 3 and falls back to zero by about day 7, so the person recovers in about a week. The right graph, for a chronic disease such as tuberculosis, shows the same scale over twelve months. The curve rises and then stays high for the whole year, so the person is still ill after many months.
The two graphs show the difference. The left graph is over ten days, and the right is over twelve months. Notice the units. The time scales are very different.
Why a chronic disease harms health more
A person with a chronic disease is ill for a long time, so the effect on health is more drastic.
The body is always short of strength. The person may lose weight, feel tired and be unable to work for long.
A student may miss many months of school.
The family loses the person's income and spends money on treatment, so food for the family may be less.
Worry and loneliness can add to the physical illness.
A person with an acute disease also feels unwell, but only for a few days. Recovery comes soon and health is little affected.
Days lost to illness
The simulation compares a person who has several short illnesses in a year with another person who has one long illness. Take a month as 30 days.
Try it in Python
The program lists four illnesses and the days each one lasts. It calls an illness chronic if it lasts 30 days or more. This is only a rule to practise with. Doctors do not use one fixed number of days.
Practise with new numbers
Common mistakes
"Acute means mild." Acute means short. Some acute diseases are serious while they last.
"Chronic means very painful." Chronic means long-lasting. The pain can be small, but the long time harms health.
"A chronic disease can be cured in a week." If it were cured in a week, it would not be chronic.
"Symptoms and signs are the same." Symptoms are what the patient feels. Signs are what a doctor finds.
Remember these
A disease is a failure of some part of the body to work well.
Symptoms are what the patient feels. Signs are what the doctor finds by examining or testing.
Acute diseases last a short time, for example a common cold.
Chronic diseases last a long time, even for life, for example tuberculosis and elephantiasis.
A chronic disease harms overall health much more than an acute one.
Check yourself
Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.
What is the difference between an acute and a chronic disease?
Give one example of each.
Why does a chronic disease harm a person's health more than an acute disease?
Imran has a cough. Is the cough a symptom or a sign? What would a doctor look for as signs?
A cold lasts 7 days. A long illness lasts 3 months of 30 days each. How many times more days is the long illness?
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