What Are Germs? The term "germs" refers to the microscopic bacteria, viruses, fungi, and protozoa that can cause disease. Washing hands well and often is the best way to prevent germs from leading to infections and sickness. Bacteria Bacteria are tiny, single-celled organisms that get nutrients from their environments. Some bacteria are good for our bodies — they help keep the digestive system in working order and keep harmful bacteria from moving in. Some bacteria are used to make medicines and vaccines. But bacteria can cause trouble too, as with cavities, urinary tract infections, ear infections, or strep throat. Antibiotics are used to treat bacterial infections. Viruses Viruses are even smaller than bacteria. They aren't even a full cell. They are simply genetic material (DNA or RNA) packaged inside of a protein coating. They need to use another cell's structures to reproduce, which means they can't survive unless they're living inside something else (such as a person, animal, or plant). Viruses can only live for a very short time outside other living cells. For example, viruses in infected body fluids left on surfaces like a countertop or toilet seat can live there for a short time, but quickly die unless a live host comes along. Once they've moved into someone's body, though, viruses spread easily and can make a person sick. Viruses are responsible for some minor sicknesses like colds, common illnesses like the flu, and very serious diseases like smallpox or HIV/AIDS. Antibiotics are not effective against viruses. Antiviral medicines have been developed against a small, select group of viruses. Fungi Fungi (pronounced: FUN-guy) are multicelled, plant-like organisms. A fungus gets nutrition from plants, food, and animals in damp, warm environments. Many fungal infections, such as athlete's foot and yeast infections, are not dangerous in a healthy person. People who have weakened immune systems (from diseases like HIV or cancer), though, may develop more serious fungal infections. Protozoa Protozoa (pronounced: pro-toe-ZO-uh) are one-celled organisms, like bacteria. But they are bigger than bacteria and contain a nucleus and other cell structures, making them more similar to plant and animal cells. Protozoa love moisture, so intestinal infections and other diseases they cause, such as amebiasis and giardiasis, often spread through contaminated water. Some protozoa are parasites, which means that they need to live on or in another organism (like an animal or plant) to survive. For example, the protozoa that causes malaria grows inside red blood cells, eventually destroying them. Some protozoa are encapsulated in cysts, which help them live outside the human body and in harsh environments for long periods of time. Back to Articles Related Articles Hand Washing: Why It's So Important Did you know that the most important thing you can do to keep from getting sick is to wash your hands? If you don't wash your hands frequently, you can pick up germs from other sources and then infect yourself. Read More Fighting Germs Germs are tiny organisms that can cause disease - and they're so small that they can creep into your system without you noticing. Find out how to protect yourself. Read More Food Poisoning The germs that get into food and cause food poisoning are tiny, but can have a powerful effect on the body. Find out what to do if you get food poisoning - and how to prevent it. Read More Ringworm Ringworm isn't a worm at all - it's the name for a type of fungal skin infection. The good news is that ringworm is easy to treat. Read More STDs (Sexually Transmitted Diseases) You've probably heard lots of discouraging news about sexually transmitted diseases. The good news is that STDs can be prevented. Find out how to protect yourself. Read More Food Safety Learn why food safety is important and how you can avoid the spread of bacteria when you are buying, preparing, and storing food. Read More MRSA MRSA is a type of bacteria that the usual antibiotics can't tackle anymore. The good news is that there are some simple ways to protect yourself from being infected. Find out how. Read More 5 Ways to Fight the Flu Get tips for fending off the flu in this article for teens. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.