Fever occurs when the immune system works harder. This is usually the case when the body wants to protect against pathogens. Fever can also be caused in very stressful phases of life, when the immune system works harder, for example, by an increased cortisol release. However, if the fever occurs without any further symptoms over a longer period of time and repeatedly, a diagnostic clarification should be carried out, since even serious illnesses can be the cause.
If the cause of the fever is not found, this is called fever of unknown origin (Fever of unknown origin).
Possible causes must always be considered viral or bacterial infections, autoimmune diseases and cancer. In any case, the HIV status is in need of clarification if fever should be noticed without further symptoms.
Diseases that are sometimes difficult to diagnose may initially only be associated with the symptom of fever. These include, for example, pus accumulations (abscesses) in organs or inflammation of the bone marrow (osteomyelitis). M. Still - a subset of rheumatoid arthritis - may be associated with recurrent fever without any further symptoms. Also, sarcoidosis, a disease that can affect the lungs, skin and joints, can only be noticed by high fever.
Furthermore, with long-lasting fever should be thought of possible causes such as malignant lymphoma and leukemia. In part, repeated fever is triggered by pulmonary embolism, which does not otherwise become symptomatic.
Medications can also cause high fever, which is referred to as drug fever. The triggering drugs include, for example, cytostatics and antibiotics. Also, various inherited (hereditary) fever syndromes can cause fever without further symptoms.
It is important to consult a doctor if the fever persists. In addition, sufferers should pay attention to whether other symptoms, such as abdominal pain or joint complaints, have occurred independently of the recent fever. In the foreground is initially the questioning to determine possible causes.
This is followed by a physical examination, paying particular attention to swollen lymph nodes or an enlarged liver. Furthermore, a blood collection is important, which can give evidence of infections or disorders in the formation of red and white blood cells. Also, the blood should be tested for HIV ( see: HIV test).
To detect certain diseases - such as sarcoidosis - an X-ray of the lung should be made. In some cases it may be necessary to take a sample from the bone marrow. This is called bone marrow puncture and is done, for example, when there is a suspicion of leukemia. In addition, further equipment examinations such as ultrasound, MRI or CT can be used to diagnose. Another method that can be used to detect both infections and cancers is so-called positron emission tomography (PET).
If all sorts of diagnostic tests have remained unknowable, it is still important to keep an eye on the fever and development. It is important to pay attention to other possible symptoms that may be related to the fever.
In some cases, an infection - for example, with HIV - is not detectable and a blood test should be repeated after a few weeks. Repeated examinations of the blood picture at the doctor are appropriate for persistent fever.
It should be clarified that fever without symptoms can be triggered by many different causes. Depending on the cause behind it, the prognosis is good or bad. In general, however, it can be assumed that the prognosis is good if no cause for the fever could be found within half a year.
The examination of the blood picture is an important part of the diagnosis when it comes to fever without symptoms. In the blood picture red and white blood cells and platelets (platelets) are counted. This indicates whether the cells in the blood are normal, too low or too high. A sub-form of the fever of unclear origin is the so-called neutropenic fever, which can be triggered for example by certain drugs. This is a drop in neutrophil granulocytes, which are part of the white blood cells and are important for the immune system. If the neutrophils are low in the blood picture, fever is often the only symptom. Nevertheless, it is a serious condition, because the immune system is greatly weakened by the lack of defense cells and therefore favors serious infections.
If the fever recurs, one also speaks of recurrent fever. It is important that recurring fever, which can not be associated with an infection, is clarified.
On the one hand recurrent fever can be triggered by a collection of pus (abscess) in the body. Normally, such pus buildup is also noticeable by pain, but, especially if it is due to internal organs, it can not cause any further symptoms.
Furthermore, Still's disease, a special form of rheumatoid arthritis, is a recurrent source of fever. Again, other symptoms that accompany the fever are possible. However, the disease can initially manifest only through fever.
Hodgkin's disease, which is a malignant tumor of the lymphatic system, can also be associated with recurrent attacks of fever for weeks to months.
The inherited familial Mediterranean fever can cause recurrent fever episodes lasting up to three days. It often occurs in connection with abdominal pain, but can also occur without it. The first fever rush usually occurs before the age of 20.
An exact duration can not be given for fever without symptoms. It should be done in any case a cause determination. Usually, the fever then sets in with the treatment. In any case, it is important to clarify persistent or recurring fever without symptoms, but also with symptoms.