Learn Science »

Infectious Diseases - Science Lessons for Grade 5 Students

Have you ever had a common cold? How did you feel when you had the cold? What do you think made you sick?

We sometimes feel sick because we have a disease. Diseases can make us ill.

Micro-organisms that cause diseases

Many diseases such as the common cold and influenza (flu) are caused by harmful micro-organisms. These harmful micro-organisms are called germs.

The two most common types of micro-organisms that cause us to get sick are bacteria and viruses.

How diseases spread

Do you notice that sometimes when you get sick, other people in your family or class get sick too? Why do you think this is so? People often get sick at the same time because germs can be easily spread from one person to another. A disease that can be spread in this way is an infectious disease. Let us look at some of the ways in which diseases are spread.

Diseases spread through the air

Imagine that a person has a cold. When he sneezes, spits, or coughs, germs in tiny droplets of water get into the air. If other people nearby breathe in the germs, they can also get a cold.

Diseases can be spread through the air. The common cold, influenza and tuberculosis are some diseases that can be spread through air.

Diseases spread by physical contact

Germs can also be spread by sharing personal items such as handkerchiefs, brushes, towels, food and drinks. The common cold, influenza, ‘red eye’ and some skin diseases are examples of infectious diseases spread by physical contact.

Diseases spread through good and water

Germs can be found in dirty food and water, and rotten or uncooked food. When we drink dirty water or eat such foods, the germs enter bodies and make us sick. Food poisoning, diarrhea and cholera are examples of infectious diseases that are spread through food and water.

When food such as bread and fruits get too old, a fungus called mould begins to grow on them. This mould is poisonous and will make you sick if you eat mouldy food.

Diseases spread by animals

Animals such as houseflies, cockroaches and rats often carry germs because they live and feed in dirty places. When these animals move to places where we eat or onto our food, the germs can be passed to us. Food poisoning, cholera and typhoid fever are examples of infectious diseases that can be spread by animals.

Did you know that mosquitoes can also spread diseases? If a mosquito bites a person with a disease such as malaria or dengue fever, it then carries the germs that cause the disease. The disease can be passed on to any other people that the mosquito bites. Malaria is spread by the Anopheles mosquito, but the disease dengue fever is spread by the Aedes mosquito.

Preventing the spread of diseases

Most germs do not make us sick because our bodies are able to fight them off. We get sick when we do not take good care of ourselves. When our body becomes weak, germs can enter and easily make us sick.

You need to stay clean and healthy to protect your body from diseases. Wash your body, hair and hands regularly.

Remember, germs can also spread through personal items such as handkerchiefs, towels and brushes. Do not share these items with others.

Eating clean and healthy food

Eating a healthy and balanced diet with lots of fresh fruits and vegetables will prevent you from getting sick. Cooking kills germs. Food such as meat and seafood should be well cooked before you eat them.

Expired food may contain germs. Do check the expiry date before you buy any food. You should not eat or drink anything that has expired.

Here are some ways to prevent the spread of diseases:

  • Keep food covered with a food cover.
  • Wash fruits and vegetables.
  • Store food in a refrigerator to help keep germs away.
  • Do not share your food or drinks with other people.
  • The water you use for drinking needs to be boiled. Boiling kills germs in water. You can also drink bottled water that you buy from the supermarket.

Keeping things clean

It is important to clean your home regularly to prevent the spread of diseases. Bathrooms, toilets, floors and tables should be wiped and cleaned with disinfectants. A disinfectant is a liquid that kills germs. Garbage should be properly sealed and stored in rubbish bins.