Infection

An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of the host tissues to the infectious agent and the toxins it produces. An infectious disease is an illness resulting from an infection, and some infectious diseases are also communicable. Infections can be caused by a wide range of pathogens, most prominently bacteria and viruses, and hosts fight them with the immune system through an innate response, often involving inflammation, followed by an adaptive response. Treatment depends on the pathogen: antibiotics for bacteria, antivirals, antifungals, antiprotozoals and antihelminthics for parasitic worms. The branch of medicine that focuses on infections is infectious diseases.