Fever may last long in some infections with subacute or chronic course. Unwanted are the iatrogenic infections at catheterisation or at fistula treatment. They cause big troubles and may have untypical course associated with fever. Deep mycosis and tuberculosis, complications of AIDS, complications of immunosuppressive treatment are accompanied by fever. Viral infections, ricketsioses and chlamydia infections are accompanied by fever and lymphadenopathy.
Neoplastic processes are very serious problem.
In some of them, fever of unknown origin may be present for a long time. Sometimes after months or even after year or two, other symptoms of neoplastic disease may be detected. Acute leukemia may be, at the beginning, considered to be an infectious disease. The temperature reaches up to 40 . Fever may accompany also the solid tumours.