disease or disorder infectious disease diseases infectious diseases infectious disorder ID infectious infectious diseases and manifestations infection transmissible disease disease by infectious agent clinical infection communicable disease Replaces 'infection' in disease hierarchy. OBI imported term infection is moved to pathologic process. This class is a container class for infectious diseases, not the process of infection itself. A disorder resulting from the presence and activity of a microbial, viral, or parasitic agent. It can be transmitted by direct or indirect contact. infectious disease