Infection

Infection is the invasion of an organism's tissues by disease-causing agents, their multiplication, and the reaction of host tissues to these organisms and the toxins they produce. Infectious disease, also known as transmissible disease or communicable disease, is illness resulting from an infection.

Infections are caused by agents including viruses, viroids, prions, bacteria, nematodes, arthropods, fungi, and other macroparasites.

Hosts can fight infections using their immune system. Mammalian hosts react to infections with an innate response, often involving inflammation, followed by an adaptive response.

Specific medications used to treat infections include antibiotics, antivirals, antifungals, antiprotozoals, and antihelminthics. The branch of medicine that focuses on infections is referred to as Infectious Disease.

