An infectious disease specialist has specialized training in the diagnosis and treatment of contagious diseases.Infectious diseases, also known as contagious or transmissible diseases, are those that stem from pathogen from a host organism. These infections may spread to other carriers through physical touch, airborne inhalation, bodily fluids or contaminated foods.Infectious disease specialists identify whether the disease is caused by bacteria, a virus, a fungus or a parasite often through blood tests and then determine what course of treatment, if any, is necessary.

An internist is a physician who focuses on the diagnosis and treatment of conditions that affect the adult population—both acute and chronic.These doctors are often who adults see as their primary physicians because they treat a broad range of illnesses that do not require surgical or specialist interventions. They also work to help a patient maintain optimal health in order to prevent the onset of disease.In addition to treating the common cold and flu, internists also treat chronic diseases like diabetes and heart disease.

A nephrologist is a physician who is specially trained to diagnose and treat conditions affecting the kidneys or renal system. A nephrologist will determine through urine analysis, blood test, X-ray, sonogram, or kidney biopsy how well the kidneys are functioning and will then prescribe a special diet and exercise program, medication or dialysis - a process by which a machine filters the blood when the kidney is no longer capable of doing so.