Viral infections: Viruses are very tiny infectious organisms. They’re even smaller than bacteria. On the most basic level, a virus is composed of a piece of genetic material that’s surrounded by a protein shell.

Possible treatments: Most of the time, the treatment of viral infections centers on relieving symptoms until your immune system clears the infection. In some cases, antiviral drugs may be available to help treat a viral infection. Some examples of viral infections for which antivirals are available to include HIV, herpes, and hepatitis C.

Bacterial infections: Bacteria can be found in all sorts of environments, including soil, bodies of water, and in or on our bodies. Some can survive extreme temperatures or even radiation exposureTrusted Source.

Treatments: Bacterial infections are most often treated with antibiotics. Antibiotics are medications that affect bacterial growth. They can either impede bacteria from multiplying or kill them outright.

Fungal infections: Fungi are another diverse group of organisms that can include things like yeasts and molds. They can be found throughout the environment, including in the soil, indoors in moist areas like bathrooms, and on or in our bodies.

Treatments: Fungal infections can be treated with antifungal medications. The type of medication that you’re prescribed will depend on the type of fungal infection you have.

Parasitic infections: Parasites live on or in a host organism and get food or other nutrients at the host’s expense. There are three types of parasites that can cause illness in humans:

Protozoa: Small, one-celled organisms.

Helminths: Larger, worm–like organisms.

Ectoparasites: Organisms such as fleas, ticks, and lice.

Treatments: As with bacterial and fungal infections, there are specific drugs available to treat a parasitic infection. The type of antiparasitic medication that you’ll need to take will depend on the type of parasite that’s causing your infection.