CONTENTS 4 6 8 10 12 14 16 18 Your Amazing Body When Germs Attack All about the Immune System White Blood Cells Antibodies Immunity Vaccines Immune System at Work Immune System Disorders Getting Better When to see a Doctor Antibiotics Healthy Habits Glossary Online Resources Index 20 22 24 26 28 30 31 32
4 YOUR AMAZING BODY You are amazing So is your body Most of the time your body works just fine But sometimes germs invade it Germs can make you sick When this happens your immune system works to fight the infection
GET TO KNOW GERMS Germs are tiny organisms They can live inside people plants and animals There are four main types of germs VIRUSES Viruses are parasitic This means they cannot survive on their own They require a host cell to reproduce BACTERIA Bacteria are single celled creatures They can survive on their own or inside another living organism PROTOZOA FUNGI Protozoa are single celled Fungi are plant like creatures Some can organisms They get their survive on their own food from people plants Others are parasitic and animals 5
