We all get sick from time to time. Wintertime, in particular, brings with it colds and flue.

Symptoms may include feeling hot and cold, a runny nose, streaming eyes, headaches, tiredness, loss of appetite, then after a few days (or sometimes longer), we start to feel better and are back to normal. So what is happening? Why do we feel so terrible? How do we get better? What is going on inside our bodies?

Let’s investigate…

Infection is the invasion of pathogenic (disease-causing) microorganisms in the body and the body’s response to that.

Pathogenic microorganisms, commonly called germs or bugs, are all around us. They can be easily transmitted from one person to another. Once they get past your skin (your first line of defence), they get into your body, your bloodstream and your cells. At this point, your immune system (your second line of defence) kicks in and fights back to destroy the pathogens causing infection.

The immune system

The immune system consists of cells, tissues and organs that work together to protect you. We explore the immune system and how it responds to various microorganisms. In the article The body’s second line of defence, we look at microorganisms, including some of the pathogens that cause sickness.

We find out what happens when your immune system doesn’t work through the story of David Vetter who lived in a sterile bubble all his life.

We also take a look at vaccination. This is a way of preventing some diseases by using your immune system to protect you. We look at the history of vaccination, as well as current immunisation in New Zealand. This is supported by activities including an investigation into some of the ethical issues surrounding vaccination.

Māori perspectives

We explore rongoā – the Māori term for medicines that are produced from native plants in New Zealand. Many of these plants were and are still used to fight infection. Find out more in the article Rongoā Māori and then follow up with the activity Using rongoā Māori.

Meet the scientists

Scientists from the Malaghan Institute of Medical Research in Wellington share their research. The article Hookworm and allergies profiles the work of Professor Graham Le Gros, who is working on a vaccine against asthma and allergies. Dr Joanna Kirman explores infectious diseases, like tuberculosis, and how they affect the immune system. This helps her team find cures for these diseases. Dr Bridget Stocker and Dr Mattie Timmer design drugs and make molecules to improve vaccines.

We also have some great activity ideas. Find out how to extract DNA from a tomato – it’s easy! – or learn how immune cells fight viral infection through playing a card game

Being a scientist is a lot like being a detective – you have to think of cunning ways to solve problems and find the answers.

Dr Joanna Kirman (Malaghan Institute of Medical Researh)

Key terms

For explanations of key concepts, see Fighting infection – key terms

Published 2 November 2010