Clinical microbiology is concerned with infectious microorganisms. Various bacteria, algae and fungi are capable of causing disease.

Disease causing microorganisms have been present for millennia. Examples include anthrax, smallpox, bacterial tuberculosis, plague, diphtheria, typhoid fever, bacterial diarrhea, and pneumonia. While modern technological advances, such as mass vaccination, have reduced the threat of some of these diseases, others remain a problem. Some illnesses are re-emerging, due to acquisition of resistance to many antibiotics. Finally, other diseases, such as the often lethal hemorrhagic fever caused by the Ebola virus, have only been recognized within the past few decades.

Many bacterial diseases have only been recognized since the 1970s. These include Legionnaires' disease, Campylobacter infection of poultry, toxic shock syndrome, hemolytic uremic syndrome, Lyme disease, peptic ulcer disease, human ehrlichiosis, and a new strain of cholera. Clinical microbiology research and techniques were vital in identifying the cause of these...