By printing and/or reading this article, you agree that you accept all terms and conditions of use, as specified online.


Health NewsThey are invisible to us, but each day we are exposed to multitudes of very tiny microorganisms. Microorganisms live everywhere - in air, soil, rock and water. For the most part, they do us no harm, but sometimes we encounter disease-causing (pathogenic) microorganisms that make us sick. These can be spread to humans from:

Once microorganisms invade our bodies, they can settle in. They can gobble up nutrients and energy, and can produce toxins, which are like poisons. Those toxins can cause symptoms of common infections, like fevers, sniffles, rashes, coughing, vomiting and diarrhea. (Read about "Diarrhea") There are four major groups of microorganisms: bacteria, viruses, fungi and protozoa (a type of parasite). Disease microorganisms (most people call them germs) can be from any of these four categories.


Bacteria are microscopic living things that have only one cell (unicellular) and are one of three shapes, rods, balls or spirals. Some bacteria cells exist as individuals while others cluster together to form pairs, chains, squares or other groupings. Vast numbers of bacteria live in, and on, our bodies. Some are beneficial. For example, some bacteria help us digest food, destroy disease-causing cells and give the body needed vitamins. (Read about "Vitamins & Minerals") However, some types of infectious bacteria can make you ill. Some examples of diseases caused by bacteria are:

There are other bacteria that can infect people, according to the Centers for Disease Control and Prevention (CDC), they include:


Viruses are the most primitive of microorganisms and are much smaller than bacteria. A virus is basically a tiny bundle of genetic material carried in a shell called the viral coat or envelope. Viruses only exist to reproduce. To do that, they have to take over suitable host cells. They invade the cells and once inside, multiply, killing the host cells in the process. This is what makes you sick. Viruses are easily destroyed by disinfectants outside the body, but can be difficult to eliminate once infection has taken place. The following are examples of viral infections:

Some other viruses that can make people sick, according to the Food and Drug Administration (FDA) include:


There are many, many different kinds of fungi, but only a small number of them make us sick. A fungus is actually a primitive plant that is found in air, in soil, on plants and in water. Some common fungi include mushrooms, yeast, mold and mildew. The body normally hosts a variety of fungi. Some of these are useful to the body, but others may form infections. A fungal infection of humans is called a mycosis. Mycoses can affect skin, nails, hair and internal organs. Some examples of common fungal infections include:

Other fungal infections may affect internal organs such as the lungs. Some examples of fungal lung infections are:

People with compromised immune systems such as HIV infection or chronic lung disease are particularly at risk from these types of respiratory fungal infections. (Read about "The Immune System" "Chronic Obstructive Pulmonary Disease")


Protozoa are a group of microscopic, single-celled animals. They can be free-living or parasitic in nature. While protozoa can be an important source of food for animals like snails, clams and sponges, they can also cause serious infections in humans. Protozoa can be transmitted to the body by eating contaminated food or water, person-to-person contact, or through the bite of an insect like a mosquito or fly. While many protozoan infections are more common in the tropics and subtropics, they can also affect people in temperate zones as well. Some common examples of protozoa illnesses are:

Protect yourself

The best way to protect yourself from germs is to steer clear of the things that can spread them. Cover your nose and mouth when you sneeze and cover your mouth when you cough to keep from spreading germs. Remember the two words germs fear - soap and water. According to the Centers for Disease Control and Prevention, washing your hands with soap and water is one of the best ways to prevent infectious disease. Wash your hands every time you cough or sneeze, before you eat or prepare foods, after you use the bathroom, after you touch animals and pets, after you play outside and after you visit a sick friend or relative. Boil water if you don't know that is it safe to consume and make sure food is fresh and has been stored properly. (Read about "Food Safety")

All Concept Communications material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.

© Concept Communications Media Group LLC

Online health topics reviewed/modified in 2020 | Terms of Use/Privacy Policy

By printing and/or reading this article, you agree that you accept all terms and conditions of use, as specified online.