Fever is elevated body temperature (> 37.8° C orally or > 38.2° C rectally) or an
elevation above a person's known normal daily value by a resetting of the temperature
set point in the hypothalamus at higher value.
Hyperthermia: Elevated body temperature that is not caused by a resetting of the
temperature set point in the hypothalamus
During a 24-h period, temperature varies from lowest levels in the early morning to
highest in late afternoon. Maximum variation is about 0.6° C.
Consequences of fever
Modest transient core T ↑(ie, 38° to 40°) well tolerated by healthy adults-usually.
Extreme temperature elevation (typically > 41° C) may be damaging.
1. Organ failure; Protein denaturation occurs, and inflammatory cytokines that
activate the inflammatory cascade are released > cellular dysfunction >.
2. DIC < The coagulation cascade is also activated.
3. Physiologically stress adults with pre-existing cardiac or pulmonary
insufficiency.( fever can ↑ BMR by ~10 to 12% for every 1° C ↑ over 37° C)
4. Worsen mental status in patients with dementia.
5. Febrile seizures in children.
Many disorders can cause fever. They are broadly categorized as
1. Infectious (most common)
3. Inflammatory (including rheumatic, nonrheumatic, and drug-related)
Acute (ie, duration ≤ 4 days) fever in adults is highly likely to be infectious.
Fever due to a noninfectious cause, the fever is almost always chronic or recurrent.
Isolated, acute febrile event in patients with a known inflammatory or neoplastic
disorder is still most likely to be infectious.
1. Upper and lower respiratory tract infections
2. GI infections
4. Skin infections
Most acute respiratory tract and GI infections are viral.
Patient factors include health status, age, occupation, and risk factors (eg,
hospitalization, recent invasive procedures, presence of IV or urinary catheters, use of
External factors are those that expose patients to specific diseases—eg, through
infected contacts, local outbreaks, disease vectors (eg, mosquitoes, ticks), a common
vehicle (eg, food, water), or geographic location (eg, residence in or recent travel to
an endemic area).
Some Causes of Acute Fever
Upper or lower respiratory tract infection
IV catheter infection
UTI (particularly in patients with an indwelling catheter)
Pneumonia (particularly in patients using a ventilator)
Surgical site infection (postoperatively)
Deep venous thrombosis or pulmonary embolism
Diarrhea (Clostridium difficile–induced)
Travel to endemic Malaria
Dengue fever (less common)
Vector exposure (in Ticks: Rickettsiosis, ehrlichiosis, anaplasmosis, Lyme disease,
Mosquitoes: Arboviral encephalitis
Wild animals: Tularemia, rabies, hantavirus infection
Domestic animals: Brucellosis, cat-scratch disease, Q fever,
Reptiles: Salmonella infection
Bats: Rabies, histoplasmosis
Immunocompromise Viruses: VZV or CMV infection
Bacteria: Infection due to encapsulated organisms (eg,
pneumococcus, meningococcus), Staphylococcus aureus,
gram-negative bacteria (eg, Pseudomonas aeruginosa),
Nocardia sp, or Mycobacteria sp
Fungi: Infection due to Candida, Aspergillus, Zygomycetes,
Histoplasma, or Coccidioides sp or Pneumocystis jirovecii
Parasites: Infection due to Toxoplasma gondii, Strongyloides
stercoralis, Cryptosporidium sp, microsporidia, or
Cystoisospora (previously Isospora) belli
MDMA, or Ecstasy
History of present illness should cover
o Magnitude of fever
o Duration of fever
o Method used to take the temperature.
1.True rigors (severe, shaking, teeth-chattering chills—not simply feeling cold)
suggest fever due to infection but are not otherwise specific.
2. Pain; in the ears, head, joints etc.
3. Other localizing symptoms; nasal congestion and/or discharge, cough, diarrhea, &
urinary symptoms (frequency, urgency, dysuria).
4. Rash (including nature, location, and time of onset in relation to other symptoms)
5. Infected contacts and their diagnosis should be identified.
Review of systems
Symptoms of chronic illness; recurrent fevers, night sweats, and weight loss.
Past medical history
1. Recent surgery
2. Known disorders that predispose to infection (eg, HIV infection, diabetes, cancer,
organ transplantation, sickle cell disease, valvular heart disorders—particularly if an
artificial valve is present)
3. Known disorders that predispose to fever (eg, rheumatologic disorders, SLE, gout,
sarcoidosis, hyperthyroidism, cancer)
4. Recent travel include location, time since return, locale (eg, in back country, only
in cities), vaccinations received before travel, and any use of prophylactic antimalarial
drugs (if required).
5. Possible exposures (eg, via unsafe food or water, insect bites, animal contact, or
6. Vaccination; hepatitis A and B and against organisms that cause meningitis,
influenza, or pneumococcal infection
1. Known to cause fever
2. Predispose to infection (eg, corticosteroids, anti-TNF drugs, chemotherapeutic and
antirejection drugs, other immunosuppressants)
3.Illicit use of injection drugs (predisposing to endocarditis, hepatitis, septic
pulmonary emboli, and skin and soft-tissue infections)
Performance of the various types of fever
a) Fever continues
b) Fever continues to abrupt onset and remission
c) Fever remittent
d) intermittent fever
e) undulant fever
f) Relapsing fever
Do not fluctuate more than 1oc during 24 hours but no time touching the base line
Fluctuation exceeds 2oc but do not touches the base line
4. Kawasaki's disease
Continuous undulating fever
eg- Typhoid, Brucellosis
Fever only present for few hours.
Daily fever spikes- abscess, pneumonia etc
Tertian fever-(Alternate days)- P.vivax, P. falciparum
Quartan fever-(Every 3rd day) –P.malariae
Saddle back fever-(fever for some days and then normal for few days and again fever)
eg- leptospirosis, Borrelia
Pel-Ebstein fever – (long periods of normal or low temperature)
eg- Hodgkin’s lymphomas, other lymphomas
Step Ladder Type Fever
Fever increases as step ladder type fashion.
Eg- Typhoid fever
Fever With Chills & Rigors
2. UTI- Pyelonephritis
3. Cholecystitis/ ascending cholangitis
Low Grade Fevers
Chronic inflammatory conditions and in malignancies
Fever is most accurately diagnosed by measuring rectal temperature. Oral temperatures are normally about 0.6° C lower and may
be falsely even lower for many reasons, such as recent ingestion of a cold drink, mouth breathing, hyperventilation, and
inadequate measurement time (up to several minutes are required with mercury thermometers). Measurement of tympanic
membrane temperature by infrared sensor is less accurate than rectal temperature.
Tachypnea, tachycardia, or hypotension.
General appearance; any weakness, lethargy, confusion, cachexia, and distress.
particularly petechial or hemorrhagic rash and any lesions or areas of erythema or
blistering suggesting skin or soft-tissue infection.
Lymphadenopathy; Axillae and epitrochlear and inguinal
In hospitalized patients, presence of any IVs, NGTs, urinary catheters..Etc.
Surgical sites If any recent Sx.
Head and neck examination
Tympanic membranes: Examined for infection
Sinuses (frontal and maxillary): Percussed
Temporal arteries: tenderness
Nose: Inspected for congestion and discharge (clear or purulent)
Eyes: conjunctivitis or icterus
Fundi: Roth's spots (suggesting endocarditis)
Oropharynx and gingiva: inflammation or ulceration (including any lesions of
candidiasis, which suggests immunocompromise)
Neck: meningismus, lymphadenopathy
The lungs; crackles or signs of consolidation, and the heart; murmurs (IE).
The abdomen; hepatosplenomegaly and tenderness (infection).
The flanks are percussed for tenderness over the kidneys (pyelonephritis).
A pelvic examination ♀ cervical motion or adnexal tenderness;
♂ genital : urethral discharge and local tenderness.
The rectum; tenderness and swelling > perirectal abscess (which may be occult in
All major joints are examined for swelling, erythema, and tenderness (suggesting a
joint infection or rheumatologic disorder).
The hands and feet; for signs of endocarditis, splinter haemorrhages/Osler's
The following findings are of particular concern:
Altered mental status
Headache, stiff neck, or both
Petechial skin rash
Significant tachycardia or tachypnea
Temperature > 40° C or < 35° C
Recent travel to malaria-endemic area
Recent use of immunosuppressants
Headache, stiff neck, and petechial or purpuric rash > meningitis.
Tachycardia, tachypnea, with or without hypotension or mental status changes >
Malaria > traveled to an endemic area.
Generalized adenopathy may occur in older children and younger adults who have
acute mononucleosis; it is usually accompanied by significant pharyngitis, malaise,
Primary HIV/ secondary syphilis should be suspected in patients with generalized
adenopathy, sometimes accompanied by arthralgias, rash, or both.
HIV infection develops 2 to 6 wk after exposure (although patients may not always report unprotected sexual
contact or other risk factors).
Secondary syphilis is usually preceded by a chancre, with systemic symptoms developing 4 to 10 wk later.
Petechial or purpuric rash > meningococcemia, DF, DHF, Rocky Mountain spotted
fever (particularly if the palms or soles are involved).
Classic erythema migrans rash of Lyme disease, target lesions of Stevens-Johnson
syndrome, and the painful, tender erythema of cellulitis and other bacterial soft-tissue
infections. The possibility of delayed drug hypersensitivity (even after long periods of
Patients with significant underlying disorders are more likely to have an occult
bacterial or parasitic infection. Injection drug users and patients with a prosthetic
heart valve > endocarditis.
Drug fever (with or without rash) is a diagnosis of exclusion, often requiring a trial of
stopping the drug. Eg. fever and rash begin after clinical improvement from the initial infection and without worsening
or reappearance of the original symptoms (eg, in a patient being treated for pneumonia, fever reappears without cough, dyspnea,
Mononucleosis or HIV infection: Serologic testing
Bacterial or fungal infection: Blood cultures
Meningitis: Immediate LP & IV antibiotics (head CT should be done before LP if
patients are at risk of brain herniation; IV antibiotics must be given immediately after
blood cultures are obtained and before head CT is done)
Specific disorders based on exposure (eg, to contacts, to vectors, or in endemic areas):
peripheral blood smear for malaria
Sepsis > cultures (urine and blood), CXR, SE, glucose, BUN, creatinine, lactate, &
Risk groups of IE; serial blood cultures, ECHO
Patients taking immunosuppressants require FBC; if neutropenia is present, testing is
initiated and CXR, as are cultures of blood, sputum, urine, stool, and any suspicious
1. Drugs that inhibit brain cyclooxygenase effectively reduce fever:
PCM 650-1000 mg po q 6 h
Ibuprofen 400-600 mg po q 6 h
The daily dose of PCM should not exceed 4 g to avoid toxicity; patients should be
warned not to simultaneously take nonprescription cold or flu remedies that contain
PCM. Other NSAIDs (eg, aspirin, naproxen) are also effective antipyretics.
Salicylates should not be used to treat fever in children with viral illnesses (Reye's
3. If temperature is ≥ 41° C, start other cooling measures (eg, evaporative cooling
with tepid water mist, cooling blankets).
In the frail elderly, infection is less likely to cause fever, and even when elevated by
infection, temperature may be lower than the standard definition of fever. Similarly,
other inflammatory symptoms, such as focal pain, may be less prominent.
Frequently, alteration of mental status or decline in daily functioning may be the only
other initial manifestations of pneumonia or UTI.
As in younger adults, the cause is commonly a respiratory infection or UTI, but in the
elderly, skin and soft-tissue infections are among the top causes.
Ix: urinalysis, urine culture, CXR. Blood cultures should be done to exclude