Germs live everywhere. You can find germs (microbes) in the air; on food, plants and animals; in soil and water — on just about every other surface, including your body.
Most germs won’t harm you. Your immune system protects you against infectious agents. However, some germs are formidable adversaries because they’re constantly mutating to breach your immune system’s defenses. Knowing how germs work can increase your chances of avoiding infection.
Infectious agents come in a variety of shapes and sizes. Categories include:
- Bacteria
- Viruses
- Fungi
- Protozoans
- Helminths
Bacteria
Bacteria are one-celled organisms visible only with a microscope. They’re so small that if you lined up a thousand of them end to end, they could fit across the end of a pencil eraser.
Not all bacteria are harmful, and some bacteria that live in your body are helpful. For instance, Lactobacillus acidophilus — a harmless bacterium that resides in your intestines — helps you digest food, destroys some disease-causing organisms and provides nutrients.
Many disease-causing bacteria produce toxins — powerful chemicals that damage cells and make you ill. Other bacteria can directly invade and damage tissues. Some infections caused by bacteria include:
- Strep throat
- Tuberculosis
- Urinary tract infections
