Communicable diseases

• Communicable diseases are caused by pathogens. Pathogens are microbes such as bacteria, viruses, protists and fungi. They are contagious (spread from touch.)
• Communicable diseases can be caused by things like bacteria, viruses, parasites and fungi. They're sometimes described as contagious or infectious diseases. Measles and malaria are examples of communicable diseases.
• Pathogens are microorganisms that enter the body and cause communicable (infectious) diseases. Both plants and animals can be infected by pathogens.
• Bacteria are very small cells (about 1/100th the size of your body cells), which can reproduce rapidly inside your body. They can make you feel ill by producing toxins (poisons) that damage your cells and tissues.
• Viruses are not cells. They are extremely small (about 1/100th the size of a bacterium.) Like bacteria, they can reproduce rapidly inside your body. They live inside your cells and replicate themselves using the cells' machinery to produce many copies of themselves. The cell will usually then burst, releasing all the new viruses. This cell damage is what makes you feel ill.
• There are lots of different types of protists. They're all eukaryotes and most of them are single-celled. Some protists are parasites. Parasites live on or inside other organisms and can cause them damage. They are often transferred to the organism by a vector, which doesn't get the disease itself -e.g. an insect (mosquito) that carries the protist.
• Some fungi are single-celled. Others have a body which is made up of hyphae (thread like structures.) These hyphae can grow and penetrate human skin and the surface of plants, causing diseases. The hyphae can produce spores, which can be spread to other plants and animals.
• DIRECT CONTACT - Some pathogens can be picked up by touching contaminated surfaces, including the the skin. E.g. athlete's foot is a fungus which makes skin itch and flake off. It's most commonly spread by touching the same things as an infected person, e.g. shower floors and towels.
• AIR - Pathogens can be carried in the air and can then be breathed in. Some airborne pathogens are carried in the air in droplets produced when you cough or sneeze e.g. the influenza virus that causes flu is spread this way.
• WATER-Some pathogens can be picked up by drinking or bathing in dirty water. E.g. cholera is a bacterial infection that's spread by drinking water contaminated with the diarrhoea of other sufferers.