Differences between a Bacterial Fever and a Viral Fever

Coming down with a fever is an uncomfortable and tiring health problem.  Additionally, it may not be clear what is the proper course of action to take when experiencing a fever.  Is it a bacterial fever or a viral fever?  How can you tell the difference?

Fever, or pyrexia, is a rise in internal body temperature to levels that are considered to be above normal.  Average body temperature is roughly 98.6 degrees Fahrenheit or 37 degrees Celsius.  Temperatures about about 100.4 degrees Fahrenheit or 38 degrees Celsius are considered febrile.

Although a fever can be associated with various illnesses such as cancer or result from physiological stresses such as strenuous exercise or heat stroke, it is most often associated with infection.  It is important to determine the underlying cause of the fever.  Once other conditions are ruled out, it is left to be determined whether an infection is bacterial or viral.

Viral infections

Common infections causes by a virus are referred to as a “cold”, also known as an upper respiratory infection, or a “flu.”  Typical symptoms of a viral infections include runny nose, low grade fever, sore throat, difficulty sleeping, headache, cough and nausea.  While influenza sufferers may experience similar symptoms, they often also feel intense body aches and have higher fevers.

 There are several diagnostic laboratory methods that can confirm a viral infection.  A virus specimen from the patient can be grown in a cell culture.  Virus-specific antibodies can be detected in the blood.  Virus antigens can be detected.  Virus nucleic acids can be detected.  Virus particles can be observed by electron microscopy.  Or a hemagglutination assay can be performed.

Colds cannot be treated with antibiotics or antiviral medications to hasten recovery.  Instead, medications aimed at lessening symptoms are used.  For example, a runny nose can be treated with a decongestant or a headache can be treated with acetaminophen.  Other than that, viral infections must usually simply run their course. 

If detected within the first 48 hours of illness, the duration of a flu can be shortened with antiviral medications.  In addition, vaccinations at the start of each flu season can help to prevent influenza infections. 

Bacterial infections

These are infections caused by bacteria that are not benign to the body.  Examples of bacterial infections are sinusitis, strep throat, pneumonia, urinary tract infections, or the more serious infections such as meningitis.  Symptoms differ according to the type and location of the infection.  They may include fever, cough, cold and chills.  A physician can diagnose a bacterial infection by a blood test or urinalysis. 

Bacterial infections are treated with antibiotics.  The specific location of the infection helps to determine the appropriate selection and type of antibiotic prescribed by the doctor.  Typical antibiotic treatment lasts 10 to 14 days.  Once commencing on the antibiotic regimen, one should begin to feel better in about 24 to 48 hours.  It is important to take the antibiotic as prescribed and to completion.

Other differences between bacterial and viral fevers

A viral illness typically causes wide-spread symptoms.  By contrast, a bacteria usually causes more localized symptoms.  For example, symptoms my involve the sinuses or throat. 

The color of the phlegm differs between bacterial and viral infections.  A virus may produce clear or cloudy mucous, if any.  A bacterial illness typically causes colored phlegm, such as green, yellow, bloody or brown-tinged.

Bacterial and viral illnesses also differ in terms of duration.  Most viral illnesses last 2 to 14 days, on average.  A bacterial illness commonly lasts longer than 10 days. 

Lastly, a viral infection may or may not cause a fever.  On the other hand, bacterial illnesses are known for causing fevers and they may be higher than those caused by viruses.  With bacterial infections, fevers get worse a few days into the illness rather than improving. 

It can seem confusing to distinguish whether an infection is bacterial or viral.  Recognizing the differences between the two infections gives some peace of mind, clarity and an idea of what to expect as treatment.  Regardless of the type of illness, it is vital to consult a physician to confirm a diagnosis and to obtain proper therapy.