Infectious disease is the subspecialty of internal medicine that specializes in preventing and treating diseases caused by bacteria, fungi, viruses, and parasites. Recently, due to new infectious diseases such as swine flu, bird flu (avian influenza), SARS, MERS, and COVID-19, and the reappearance of past pandemics such as malaria, tuberculosis, the role of this specialty is growing.

This specialty treats sepsis, urinary tract infection, soft tissue infection, pneumonia, endocarditis, tsutsugamushi disease, fever of unknown origin, and sexually transmitted diseases, and prevents and treats endemic diseases that can be contracted at overseas travel destinations when traveling abroad. It also provides preventive medicine and prevention guidelines to travelers with chronic diseases as well as vaccinations required for studying or working abroad.