Fever may have certain signs in relation to its course. It has diagnostic importance and certain information value. Is several disease, however, it doesn't necessarily have certain characteristics.
Fever in infectious diseases usually is of short duration.
Generally, it is limited to 2 week period. During infectious
diseases fever has the following characteristcs: sudden start of
fever, temperature over 38,5
, fever without chills,
symptoms of respiratory infection, muscle and joint ache,
headache, nausea, vomitting, diarrhea, enlarged lymph nodes or
spleen, meningeal symptoms, and dysuria.
Similarly to infectious diseases, acute leukemia or vasculitis may manifest in the same way.
Long duration (weeks or months) is always a very serious
problem. If it is not possible to determine the cause of fever
at the beginning, it is called the
fever of unknown origin
(FUO). This term is used to describe fever lasting at least 2
weeks, reaching temperatures above 38,2
, and the cause of
the origin is uncertain.
Fever may last long in some infections with subacute or chronic course. Those may be hired abscess in the abdominal cavity or in the abdominal organs (abscess of the liver, spleen, subfrenic abscess, diverticulitis and an abscess in the small pelvis).
Longlasting fever may also occur in renal infections and in intravascular infections (acute infections of the urinary tract, bacterial endocarditis).
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. In several cases fever
has typical progress (Pel--Ebstein fever at Hodgkin's lymphoma).
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. The cause may be
the obliteration of glandular ducts or necrosis of the tumour
and/or metastatic spread.
Diseases of connective tissue are accompanied by fever. It's present at rheumatic arthritis, periarteritis nodosa, systemic lupus erythematosus, and in polymyalgia rheumatica.
There are many other disorders and changes of organism in which fever develops. Those may be hidden hematomas, hemolytic crisis, pulmonary embolisation, and thermoregulatory dysfunction at metabolic and endocrine disorders. Sometimes psychogenic fever may occur. It happens in patients with psychopathology or in pharmacofags. In these cases the frequency of heart beats even at high temperatures increase only slightly.
Habitual hyperthermia (37,2--38
) is detected in
children and young women. It is associated with the signs of
psychoneurosis, asthenia, complete weakness, and insomnia. They
often have different unpleasant subjective feelings that force
them to think about their high temperature.
Drug-induced fever is a serious problem. If we take into
consideration that the patient with infection is treated by
antibiotics that may cause fever, we find out that it's an
excessive complex problem. Of medications that cause the fever
the antibiotics are most frequent (especially 
-lactamase
antibiotics and penicilins) but also sulfonamids,
nitrofurantoin, antituberculotics, barbiturates and laxatives.
Drug-induced fever doesn't have characteristic features. Most
often it occurs 5 to 10 days after the start of treatment but it
may occur also right after the first dose. Most probably, the
drug acts like an exogenic pyrogen.