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Germs: Understand and protect against bacteria, viruses and infection
Germs. Learn how germs work and what you can do to protect yourself.
By Mayo Clinic staffGerms live everywhere. You can find germs in the air, on food, plants and animals, in the soil, in the water, and on just about every other surface — including your own body.
Most germs won't harm you. Your immune system protects you against a multitude of infectious agents. However, some germs are formidable adversaries because they're constantly mutating to breach your immune system's defenses. Knowing more about how germs work can increase your chances of avoiding infection.
Infectious agents: From bacteria to worms
Infectious agents come in a variety of shapes and sizes. Categories include:
- Bacteria
- Viruses
- Fungi
- Protozoa
- 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. They're shaped like short rods, spheres or spirals.
Not all bacteria are harmful. In fact, less than 1 percent cause disease, and some bacteria that live in your body are actually good for you. For instance, Lactobacillus acidophilus — a harmless bacterium that resides in your intestines — helps you digest food, destroys some disease-causing organisms and provides nutrients to your body.
Many disease-causing bacteria produce toxins — powerful chemicals that damage cells and make you ill. Bacteria cause diseases such as:
- Strep throat
- Tuberculosis
- Urinary tract infections
Viruses
Viruses are much smaller than cells. In fact, viruses are basically just capsules that contain genetic material. They may be shaped like rods, spheres or tiny tadpoles. To reproduce, viruses invade cells in your body, hijacking the machinery that makes cells work. Host cells are eventually destroyed during this process.
Viruses are responsible for causing a wide range of diseases, including:
- AIDS
- Common cold
- Ebola hemorrhagic fever
- Genital herpes
- Influenza
- Measles
- Smallpox
Antibiotics have no effect on viruses.
Fungi
There are many different varieties of fungi, and we eat quite a few of them. Mushrooms are fungi, as is the mold that forms the blue or green veins in some types of cheese. And yeast, another type of fungi, is a necessary ingredient to make most types of bread.
Other fungi can cause illness. One example is candida — a yeast that can cause infection. Candida can cause thrush — an infection of the mouth and throat — in infants and in people taking antibiotics or who have an impaired immune system. Fungi are also responsible for such skin problems as athlete's foot and ringworm.
Next page(1 of 2)
- Understanding microbes in sickness and in health. National Institute of Allergy and Infectious Diseases. http://www3.niaid.nih.gov/topics/microbes/PDF/microbesbook.pdf. Accessed Feb. 16, 2009.
- Kok M, et al. Nature and pathogenicity of micro-organisms. In: Cohen J, et al. Infectious Diseases. 2nd ed. Philadelphia, Pa.: Mosby Elsevier; 2004. http://www.mdconsult.com/das/book/body/120681370-3/0/1209/4.html?tocnode=49351200&fromURL=4.html#4-u1.0-B0-323-02407-6..50003-9_5. Accessed Feb. 16, 2009.
- Viruses - and some virus-like agents. Microbe World. American Society for Microbiology. http://www.microbeworld.org/microbes/virus/default.aspx. Accessed Feb. 16, 2009.
- Protozoa. Microbe World. American Society for Microbiology. http://www.microbeworld.org/microbes/protista/protozoa.aspx. Accessed Feb. 16, 2009.
