It is possible for an organism to be infected by two or more infective agents. The term "super-infection" refers to the situation wherein one agent attacks first and a second one complicates the previous infection. For example, a viral infection can be complicated by a bacterial infection. If infective agents attack simulataneously, the situation is called "associated infection". For example, a patient with low immunity (AIDS, leukemia) can be attacked by many infective agents at the same time.