Common causes and types of fever

Common causes and types of fever

What are some of the most common causes of fever?

Body temperature can elevate for a variety of reasons. Some of the most common reasons why include:

  • Infections – due to a bacteria or virus coming in contact with the body (these can include colds and flu, gastroenteritis, chickenpox or infections of the ear, skin, throat, lungs, bladder or kidneys).
  • Heat exhaustion or heat stroke (due to exposure to high temperatures or prolonged strenuous exercise)
  • Extreme sunburn 
  • Teething in infants
  • An inflammatory condition, such as rheumatoid arthritis, lupus or inflammatory bowel disease (IBD)
  • Hormone disorders, such as hyperthyroidism
  • Cancer
  • Use of medications, such as antibiotics or those used to treat seizures or high blood pressure (hypertension).
  • A malignant tumour
  • Blood clots
  • Food poisoning
  • A side-effect of a vaccination, such as those for tetanus, diphtheria, pneumococcal vaccine or acellular pertussis (DTaAp).
  • The use of illicit drugs (cocaine or amphetamines) or alcohol withdrawal
  • Unidentified or ‘fever of unknown origin’ or FUO (sometimes a cause of a fever may not be able to be identified following extensive evaluation).

Terms used to characterise fever types include:

  • Persistent fever (or prolonged fever): A fever that lasts between 10 and 14 days or longer. These fevers are typically low-grade.
  • Constant fever (or continuous fever): A fever that appears to change by 1 degree within a 24-hour period. These fevers are also commonly low-grade.
  • Chronic fever: A fever that recurs for several months or years and lasts between 3 and 4 days at time. These fevers are usually of the intermittent variety.
  • Intermittent fever: Temperature fluctuates between baseline (normal) and at fever levels over the course of a single day. A fever may recur between 1 and 3 days after a previous one (which may only last a day).
  • Remittent fever: A fever may come and go, with fluctuating temperature at regular intervals.
  • Hyperpyrexia fever: A dangerously high fever (at least 41 degrees Celsius / 106 degrees Fahrenheit or higher) is considered a medical emergency and requires immediate assistance.

Common types of fever

Nasal infection as a contagious sinus disease transmitting a virusBased on the variety of underlying causes, some of the most common fever types include:

  • Viral fever: Most viral fevers caused by airborne viruses may cause accompanying symptoms of nausea and vomiting, an upset stomach and diarrhoea along with fever. These fevers usually clear with time, with or without the aid of relieving medications (over-the-counter).
  • Bacterial fever: A bacterial infection can affect almost any and every organ system in the body – namely the central nervous system (the brain and spinal cord), lower respiratory system, upper respiratory system, the genitourinary system (affecting the bladder, kidneys and urinary tract), the reproductive system, gastrointestinal system (digestive system), circulatory system (heart and lungs) and the skin. Antibiotics are necessary to treat any of these affected areas.
  • Fungal fever: A infection can also affect any organ system in the body. A physical exam and testing can determine the underlying cause of an infection. These types of related infections are typically treated with antifungal medications.
  • Animal exposure fever: A rare bacteria can be contracted by those who work closely with animals (livestock). Exposure (which can include contact with the urine of an infected animal or unpasteurised dairy products) can cause headache, muscle and joint aches, as well as fever and chills.
  • Traveller’s fever: Exposure to new foods, insects, toxins or some vaccine-preventable illnesses (such as yellow fever). Low-grade fevers can occur following the consumption of contaminated water, or uncooked fruits or vegetables, and unpasteurised dairy products. Antibiotics can be used to treat symptoms of fever, nausea, vomiting, headache and abdominal bloating.
  • Blood clot fever: Blood clots can develop in the leg (calf) and cause pain and swelling. When a portion of the clot breaks and travels through the bloodstream to the lungs causing inflammation in the blood vessels (pulmonary embolus), chest pain and breathing problems occur. Inflammation can bring on fever as well.
  • Drug (medication) fever: Starting a course of new medication can bring about fever as a side-effect. Fever typically clears with the discontinuation of the medication. In some cases, a fever following the start of a new medication can be as a result of an allergic reaction. In this instance, the development of fever is usually immediate.
  • Environmental fever: Overheating and very high body temperatures can lead to hyperthermia. This can be caused by prolonged strenuous exercise of hot and humid weather conditions. Hyperthermia (environmental fever) can result in a person experiencing lethargy, confusion and even becoming comatose. This type is considered a medical emergency and a person must be immediately taken to hospital.
  • Tumour fever: Pyrogens and chemicals can produce fever in those battling cancer, especially when tumours become infected. Medications used to treat cancer can also bring about fever side-effects as well as lead to weakened immune systems.
  • Special medical conditions: This type of fever is as a result of certain medical conditions, such as diabetes or HIV, that prevent a person’s immune system from working effectively in the body. These conditions make individuals especially vulnerable to fever-causing infections. In some instances, it may be difficult to find a cause of fever, depending on the type of disease. When a person has a condition that limits the body’s ability (immune system) to fend off infection, the symptom of fever can be dangerous or life-threatening. Fever in combination with an existing condition should be seen and treated by a medical professional as soon as possible.
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