Infectious Disease
Infectious disease specialists are called in by primary care or internal medicine physicians to treat complicated diseases caused by viruses, bacteria, or parasites. Their services are needed when a disease can not be diagnosed by routine labwork, is uncommon (e.g. tropical disease), has not responded to routine antibiotics, and might be dangerous to other patients and medical staff. Examples of diseases treated by infectious disease specialists include HIV/AIDS, malaria, tuberculosis, measles, and meningitis.Reference: http://en.wikipedia.org/wiki/Infectious_disease