Febrile Body Temperature : Causes, Symptoms, Diagnosis & Treatment

Last Updated: 29/09/2022

Febrile body temperature is an increase in thermometer readings from 38 to 39 degrees, which is manifested by a feeling of heat, headache, tachycardia and rapid breathing. It develops with some viral and all bacterial infections, inflammatory processes in the abdominal cavity, brain damage. To verify the cause of fever, a blood culture study, serological reactions, ultrasound, and radiography are used. To reduce fever, physical methods of cooling are prescribed in combination with antipyretic drugs.

Causes of febrile body temperature


In this viral process, the temperature in most cases rises sharply to 39°C within a few hours. Fever is preceded by a short prodromal period, when there is a headache and body aches, general malaise. With an increase in the thermometer, a flu patient feels a strong chill, which is replaced by fever, skin flushing. The eyes acquire a characteristic luster, the vessels of the conjunctiva are filled with blood. The duration of hyperthermia in uncomplicated forms of influenza is up to 5 days, then a critical drop in temperature occurs (sometimes below 35 degrees).

Infectious mononucleosis

The disease develops gradually, during the week there is a prodromal period with weakness, aching muscles, sore throat. The temperature in infectious mononucleosis rises to febrile, with reduced immunity, its values ​​\u200b\u200bcan reach 40-41 ° C. At the same time, severe pain in the throat and difficulty in swallowing appear, lymph nodes increase. The duration of the febrile period is 1-2 weeks. Sometimes, after the disappearance of clinical manifestations, the temperature remains subfebrile, which is due to post-viral asthenic syndrome.

Bacterial infections

Microorganisms, when released into the bloodstream, stimulate the massive production of endogenous cytokines that affect the autonomic centers of the hypothalamus. Febrile fever in bacterial diseases is often of a constant type, but the temperature curve can become undulating - the alternation of periods of elevated and normal temperature is associated with a cyclic release of bacteria into the systemic circulation. The duration of symptoms is from several days to several weeks, febrile temperature is combined with lack of appetite, exhaustion of the body. The main causes of hyperthermia:

  • Respiratory tract infections : purulent bronchitis, focal and lobar pneumonia.
  • Diseases of the ENT organs : lacunar and necrotic tonsillitis, pharyngeal abscess, purulent otitis media.
  • Intestinal infections : salmonellosis, typhoid fever, dysentery.
  • Urogenital pathology : acute pyelonephritis, purulent cystitis, adnexitis.
  • Skin lesions : boils and carbuncles, erysipelas.


Acute abdomen syndrome

Inflammatory processes in the abdominal organs provoke the synthesis of pyrogens, which are quickly absorbed into the bloodstream and act on the thermoregulation center. The body temperature of a patient with an acute abdomen is usually febrile, with chills and muscle tremors. Despite the high thermometer readings, the skin remains pale and cold to the touch, which is associated with pathological vasospasm. In addition to fever, there are local signs - severe abdominal pain, dyspepsia. With such symptoms, you should immediately consult a doctor to diagnose and eliminate the cause.

Neurological diseases

With damage to the brain tissue, febrile temperature is associated not only with the action of endogenous pyrogens, but also with a direct effect on the centers of the hypothalamus. Hyperthermia sometimes reaches 41 degrees, the general condition of the patient is severe - unbearable headaches, meningeal symptoms are observed. Then there are violations of consciousness: delirium, hallucinations, pathological drowsiness. Similar signs are characteristic of purulent meningitis, encephalitis. Fever also occurs in severe traumatic brain injury.

Complications of pharmacotherapy

Sometimes, at the beginning of antibiotic therapy for sepsis and massive bacteremia, the Jarisch-Herxheimer reaction is noted, due to such reasons as the decay of microbial cells, intoxication of the body with foreign antigens, and an uncontrolled immune response. Symptoms occur during treatment with bactericidal drugs - penicillin, vancomycin, sulfonamides. In the elderly, febrile body temperature appears after 1-2 weeks of using psychotropic drugs, which is potentiated by neuroleptic malignant syndrome. Fever is also caused by:

  • Psychostimulants : amphetamine, cocaine, MDMA (ecstasy).
  • Antiepileptic : phenytoin, carbamazepine.
  • Interferons .

Rare Causes

  • Teething in infants.
  • Hemorrhagic fevers : Magburg, Ebola, Crimean-Congo, yellow fever.
  • Parasitic infections : toxoplasmosis, cryptosporidiosis, strongyloidiasis.
  • Especially dangerous infections : plague, rabies, tularemia.
  • Vascular pathology : pylephlebitis, deep vein thrombosis.
  • Allergic diseases .
  • Iatrogenic conditions : transfusion reaction, early postoperative period, urinary tract infection when using a catheter.


If you have a fever, you should visit a general practitioner who collects an anamnesis of the disease and an initial examination of the patient. To identify the cause that provoked febrile temperature, various bacteriological studies are carried out. To study the state of internal organs and identify local pathological processes, instrumental visualization is necessary. In terms of diagnostics, the most important are:

  • Bacteriological culture . If febrile body temperature is not accompanied by local symptoms, three blood samplings are required at the height of fever and inoculation of the material on selective nutrient media. To isolate the pathogen, sputum samples, pus, and a throat swab are also used. An antibiotic susceptibility test is required.
  • Blood tests . In the general analysis, leukocytosis and an increase in ESR are detected; in a biochemical study, attention is paid to the level of acute phase proteins. Serological tests are effective in quickly identifying an infectious cause by measuring the level of specific antibodies. The viral load is quantified by PCR.
  • Ultrasound . At temperature and pain in the abdomen, a survey ultrasound of the abdominal cavity is shown, during which signs of inflammation and purulent foci are detected. According to indications, ultrasound of the lymph nodes is performed to exclude the lymphoproliferative process. With a possible vascular pathology, duplex scanning of the vessels is done.
  • Radiography . All patients undergo chest radiographs in two projections. To diagnose neurological infections, MRI or CT of the brain is used, and an EEG is additionally prescribed. If diseases of the genitourinary system are suspected, the results of excretory urography are taken into account, which helps to investigate the functional state of the kidneys.


Help before diagnosis

You can bring down the fever to 38.5 ° C using physical cooling methods - wiping the body with water at a low temperature, maintaining the humidity in the room within 50-60% and the temperature regime up to 2 degrees, using a fan. A person needs to be regularly given a warm drink to prevent dehydration. At higher thermometer numbers, it is permissible to use antipyretic drugs (paracetamol, ibuprofen). With a febrile body temperature and a sharp deterioration in the general condition, the patient needs qualified medical care.


Conservative therapy

In adults, antipyretic drugs are prescribed only if the febrile body temperature rises more than 38.5 degrees. Medicines are given to children with a fever above 38 ° C in order to prevent the development of such a formidable complication as febrile convulsions. Medicines from the group of non-steroidal anti-inflammatory drugs are used. In childhood, the use of acetylsalicylic acid is prohibited, since it can cause Reye's syndrome. In addition to symptomatic agents, drugs are used that affect the causes of fever:

  • Antibiotics . Bacteriostatic antibiotics are preferred to prevent complications. Medications continue to take the entire period of febrile fever and another 4-5 days after the normalization of body temperature.
  • Antivirals . In severe influenza, specific drugs are recommended that block the assembly of new viruses and reduce viremia. Additionally, recombinant interferons and immunoglobulins are shown that stimulate the immune system.
  • infusion solutions . With their help, eliminate the symptoms of intoxication and accelerate the excretion of toxic metabolic products. With high fever, the temperature of the infused solutions should be 2-3 ° lower. At the same time, diuretics are administered to prevent overhydration of the body.

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