Diseases – JSS3 Intermediate Science Lesson Note (Second Term)

A disease is any condition that stops the body from working the way it should. There are two main groups of disease: communicable and non-communicable.

• Cold: a person can “catch” it from a friend, so it is communicable.
• Broken leg or toothache: a person cannot “catch” these from anyone, so they are not communicable.

Behavioural objectives

1. Define disease, communicable disease and non-communicable disease.
2. Name the organisms that cause communicable diseases and give an example of each.
3. State the ways communicable diseases spread, with examples.
4. List the types of non-communicable disease, with examples.
5. Describe how to prevent communicable and non-communicable diseases.
6. Distinguish between communicable and non-communicable diseases.

What are communicable diseases?

A communicable (infectious) disease is a disease that can pass from one person to another.

• Cause: tiny living things called germs (microorganisms or pathogens).
• Pathogen: any microorganism that causes disease.
• Spread: from an infected person, animal or object to a healthy person.

What germs cause communicable diseases?

The main germs that cause disease are bacteria, viruses, protozoa and fungi.

How do communicable diseases spread?

Communicable diseases spread through the air, water and food, direct contact, vectors and infected animals.

• Airborne: through coughing or sneezing, as in tuberculosis, flu and the common cold.
• Water or food-borne: by drinking dirty water or eating contaminated food, as in cholera and typhoid.
• Direct contact: by touching an infected person or their clothes, as in ringworm and Ebola.
• Vector-borne: carried by a “messenger” such as a mosquito, as in malaria.
• Contact with infected animals: through food or objects soiled by rats, as in Lassa fever.

What is a vector?

A vector is a living organism that carries disease germs from one host to another.

• Mosquito: the female Anopheles mosquito carries the malaria parasite from person to person.
• Housefly: carries germs from dirt and waste onto food.
• Why malaria is communicable: the mosquito passes the germ on, even though people do not get it by shaking hands.

What are non-communicable diseases?

A non-communicable disease is a disease that cannot pass from one person to another.

• No germ spread: a person can sit beside someone with the illness all day and will not “catch” it.
• Causes: lifestyle choices, the environment, or the way the body is built.

What are the types of non-communicable disease?

The common types are nutritional, lifestyle, hereditary diseases and organ failure.

• Nutritional diseases: caused by lack of the right food, such as kwashiorkor (lack of protein) and scurvy (lack of vitamin C).
• Lifestyle diseases: linked to habits such as smoking or eating too much sugar or salt, as in diabetes, heart disease and hypertension (high blood pressure).
• Hereditary diseases: passed from parents to children through genes, as in sickle cell anaemia.
• Organ failure: a body part stops working properly, as in kidney failure.

How do communicable and non-communicable diseases differ?

Communicable diseases are caused by germs and spread, while non-communicable diseases do not spread.

What is the difference between preventing and controlling a disease?

Preventing a disease means stopping it before it starts, and controlling it means limiting its spread and effects once it is present.

• Prevention: acting early, for example vaccination or washing hands.
• Control: reducing the harm of a disease already present, for example treating the sick and keeping them away from others.
• Cost: it is cheaper and easier to prevent a disease than to treat it in hospital.

How can communicable diseases be prevented?

Communicable diseases are prevented by stopping germs from reaching or entering the body.

1. Immunisation (vaccination): trains the body to fight germs such as polio and measles viruses before they attack.
2. Environmental sanitation: clean gutters, cut bushes around the house to reduce mosquitoes, and dispose of refuse properly.
3. Personal hygiene: wash hands often and do not share towels or toothbrushes.
4. Boiling water: boil water you are unsure of to kill germs.

How can non-communicable diseases be prevented?

Non-communicable diseases are prevented mainly by healthy living habits.

1. Balanced diet: eat all food groups, such as carbohydrates, proteins and vitamins, and avoid too much junk food.
2. Regular exercise: walking, running or sport keeps the heart strong and prevents obesity.
3. Rest: gives the body time to repair itself.
4. Regular check-ups: visit the school clinic or a hospital even when you feel well.

Evaluation

1. Define a communicable disease and give two examples.
2. Why is malaria called a communicable disease even though you cannot get it by shaking hands?
3. Can eating too much sugar cause a communicable or a non-communicable disease? Give a reason.
4. What is the difference between preventing and controlling a disease?
5. State three ways of preventing communicable diseases.

Assignment

Draw a table with two columns, communicable and non-communicable. List four diseases in each column and state one way to prevent each disease.