Notes

Unlike chronic diseases, infectious diseases are not caused by inherited traits or diet, exercise, and drug habits. These are caused by pathogens, or microbes, which are microscopic organisms. These include bacteria, viruses, fungi, and protozoa, but not all microbes are "bad". Some of them are essential for human life and a necessary component in our bodies. The disease-causing ones are spread by physical contact, through the air (sneezes, etc.), in contaminated food and water, by animal bites and stings, and through the use of dirty needles and exchange of contaminated bodily fluids.

We have vaccines for many infectious diseases in modern medicine, so you may ask why we still see those diseases occurring. They still exist because people still spread them, plain and simple. Some choose not be vaccinated or do not have access to vaccinations, or they may live in places without proper sanitation, environments where these microbes can breed without control. This is why it is so important for everyone on the planet to have clean homes, schools, and work environments, including safe food and drinking water and access to quality health care.

Common infectious diseases are Influenza and Rhinovirus (the common cold). Other less common ones are Tuberculosis, Meningitis, and STDs, although STDs have become more common at an alarming rate.

Your body produces white blood cells, which attack and try to destroy invading pathogens before they can damage the body beyond repair. This is why HIV is so dangerous is because it weakens and eventually destroys those white blood cells, so that a person could die just from the common cold. Constant hunger and thirst can also weaken the immune system, such as in poorer areas of poverty and unclean conditions (approximately 1 in 5 people in the world to not have access to safe drinking water). In the case of a bacterial infection, usually antibiotics can be given that target and destroy the germs. We do have some anti-viral treatments for illnesses caused by viruses, but in general, viruses need to "run their course" and be primarily fought by the white blood cells. We also have anti-fungal medications for those caused by fungi.

Vaccines work by introducing a dead or modified living pathogen into the body that will prompt the white blood cells to activate and kill it. Once they have destroyed the germ once, your white cells hold the memory of how to kill it in case you are every exposed to the same microbe again. Along with vaccines, eating healthy, getting enough exercise, and drinking clean water are great ways to help avoid becoming sick.