Immunodeficiency is a pathology in which the immune system does not fulfill its protective role, leaving the body vulnerable to any infection. As a result, the patient suffers more infections than usual, in addition to becoming more severe and prolonged, responding poorly to the treatments. Immunodeficiencies may be primary or secondary. The primary ones sometimes appear for genetic causes and at other times their cause is unknown, without relation to medicines or virus infections, but only gives an inadequate functioning of the immune system. In contrast, secondary immunodeficiencies may be caused by some immunosuppressive (immunity-lowering) drugs, others that are used in chronic diseases and cancers (corticosteroids and immunosuppressants used against cancer). Other secondary immunodeficiencies may be due to infections with viruses such as HIV or AIDS, with permanent effects. Other virus infections may leave a temporary state of diminished defenses that subsequently recover.