An infectious disease physician is similar to a microbiologist, but usually has a clinical focus instead of a research focus. ID physicians gain an understanding of the many infections that can affect the human body, especially those that are hard to diagnose or treat. They study and treat infections (bacterial, fungal or viral) and tropical diseases. They evaluate patients before they travel, treat illnesses after they travel, and deal with challenges presented by hepatitis B and C, high fevers, HIV or AIDS, and infections that resist antibiotics.

ID physicians diagnose infections and consider symptom severity and duration when talking with patients about the history of their disease. They are also interested in learning about any allergies, past medical problems, medications and, when relevant, social history. Once they understand a patient’s background, ID physicians examine patients for symptoms by considering basics such as blood pressure, pulse, respiratory rate and temperature. They also often look rashes, enlarged lymph nodes and other observable symptoms that might be relevant to the situation. For example, they order blood tests, ask for imaging information (CT and MRI scans, ultrasound and X-ray), and gain information by using microscopes and cultures. Finally, they look at sensitivities.