Classification of Diseases
Senior 1 · Biology
Classification of Diseases
Lesson 1 of 5
25 min
Gatete never misses a football match and has not seen a nurse for years, but he sleeps badly, feels worried most days and spends break time alone. Uwase has asthma and carries an inhaler, yet she takes her medicine, plays in the school netball team and has many friends. Which of them is healthy? Most people answer "Gatete", because he is never ill. By the end of this lesson you should be able to explain why the answer is not so simple.
Definition
Health: "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity" (World Health Organization, 1948).
Disease: any condition in which the normal structure or working of the body, or of part of it, is damaged or impaired. Example: malaria damages red blood cells.
Symptom: something a sick person feels and reports, such as a headache. Sign: something another person can observe or measure, such as a temperature of 39 °C.
Figure 1: Health has physical, mental and social sides. A problem on one side affects the others: pain can cause worry, and loneliness can disturb sleep and appetite.
So Gatete, although never ill, is not fully healthy: his mental and social well-being are poor. Uwase has a disease (asthma), but because it is well controlled she enjoys good physical, mental and social well-being. Health is not just "not being sick".
Worked example 1: which side of health is affected?
For each case, name the side of health that is mainly affected: (a) Mugisha has a broken arm; (b) Keza feels sad and hopeless for weeks after failing an exam; (c) a new student has been left out by the class and eats alone every day.
| Practice | How it helps | In daily life in Rwanda |
|---|---|---|
| A balanced diet | provides all the nutrients for growth, energy and defence against disease (Unit 7) | beans, vegetables, fruit, milk, small fish; not too much sugar or salt |
| Clean, safe water | prevents diarrhoeal diseases such as cholera and typhoid | boil or treat drinking water; keep jerrycans clean and covered |
| Personal and food hygiene | removes pathogens before they enter the body | wash hands with soap after the toilet and before eating; cover food |
| Physical exercise | strengthens the heart, lungs, muscles and bones; improves mood | walking to school, sport, dance, Car Free Day in Kigali |
| Enough sleep | lets the body repair itself and the brain store what you learned | a regular bedtime; phones away at night |
| Vaccination | prepares the body to fight particular infections | the national immunisation programme for babies and school children |
| Avoiding tobacco, alcohol and drugs | prevents lung, liver and brain damage and addiction (Unit 12) | saying no to peer pressure |
| Talking about feelings; good relationships | protects mental and social well-being | talking to a friend, parent, teacher or counsellor |
| A clean environment | removes breeding places for mosquitoes and flies | clearing bushes and stagnant water during umuganda |
| Early health care | treats illness before it becomes serious | visiting the community health worker or health centre; joining Mutuelle de santé |
Mutuelle de santé is Rwanda's community-based health insurance, run by the Rwanda Social Security Board (RSSB). Families pay a yearly contribution for each member, and in return they pay only part of the cost when they are treated. Under the rules published in February 2026, the yearly contribution depends on the household's level in the social registry: the Government pays for the poorest, and other members pay between Rwf 3,000 and Rwf 20,000 per person. At a health centre a member pays Rwf 200 per visit, and at a hospital 10% of the bill; people classified as indigent pay nothing.
Worked example 2: what does a family pay?
A family of six is in level 3, where the contribution is Rwf 5,000 per person per year. Later, the mother is treated at a district hospital and the bill is Rwf 18,000. What does the family pay (a) for the year's contribution, (b) for the hospital treatment?
Why it matters for health: because treatment is affordable, people seek care early, before an illness becomes serious.
Warning
Common mistakes. (1) "Healthy means never being sick." A person with a well-managed condition can be healthy, and a person with no disease can be unwell mentally or socially. (2) Confusing signs and symptoms: a symptom is felt by the patient; a sign can be seen or measured by someone else. (3) Thinking that health is only the job of doctors: most of the practices in the table are things you do yourself.
What would happen if you didn't sleep? (TED-Ed). Watch for what sleep does for the body and the brain, and how missing it affects both physical and mental well-being.
Tip
Memory hook: health is a three-legged stool, physical, mental and social. If one leg is short, the stool wobbles. When asked to "explain how a practice promotes good health", name the practice, what it does in the body or mind, and which disease or problem it prevents.
Practice: health and disease
Key points
Sources and credits
Written by Ganzaa: Figure 1, the practices table, the worked examples and the practice questions.
