Communicable Diseases Are Caused by Pathogens

1. A communicable disease can spread from one organism to another, so it is also called an infectious disease.
2. Communicable diseases are caused by pathogens, which are microorganisms that cause disease.
3. Pathogens can infect both animals and plants.

How Bacteria and Viruses Make Us Ill

1. Once inside the body, bacteria and viruses can reproduce rapidly.
2. Many bacteria produce toxins, which are poisons that damage tissues and make you feel ill.
3. Viruses live and reproduce inside the body's cells, damaging and destroying them.
4. Symptoms such as fever, headaches and rashes come from the body reacting to the cell damage and toxins.

How Pathogens Spread

1. The more pathogens that enter the body, the more likely you are to become ill.
2. Pathogens can spread by direct contact between organisms.
3. They can spread through water, for example in dirty drinking water or splashes onto plants.
4. They can spread through the air, often in droplets breathed out when a person coughs or sneezes.

Reducing and Preventing the Spread

1. Good hygiene, such as washing hands and using disinfectants, removes pathogens.
2. Isolating infected people reduces the number of others they can pass the disease to.
3. Destroying or controlling vectors, such as insects, stops them carrying pathogens between hosts.
4. Vaccination protects people and animals against particular pathogens.
5. In plants, good field hygiene and removing infected plants help stop diseases spreading.