Hyperpyrexia is another term for a very high fever. It usually refers to a body temperature of more than 106.7°F or 41.5°C. Treatment may depend on the underlying cause.

Some doctors lower the measure for hyperpyrexia to include anyone with a body temperature of 106.1°F or 41.1°C and above.

Fevers, including very high fevers, are never illnesses in themselves, or the causes of illnesses. Instead, they are symptoms of other problems, such as an infection or injury. Viral or bacterial infections cause most fevers. However, in hyperpyrexia, that is not always the case.

Hyperpyrexia is an emergency that needs immediate attention from a medical professional.

Fast facts on hyperpyrexia:

  • Viruses that can cause hyperpyrexia include enterovirus infection, roseola, rubeola, and malaria.
  • Hyperpyrexia is associated with a body temperature of more than 106.7°F or 41.5°C.
  • Typically, treatment for hyperpyrexia focusses on the underlying disease, if one exists.
  • The outlook for hyperpyrexia depends on the underlying condition causing the state of very high fever.
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Hyperpyrexia can present as an adverse effect of anesthesia.

In hyperpyrexia and most other cases of fever, the brain tells the body to raise its baseline temperature above normal. The body responds to the brain’s messages and raises its temperature to a new baseline. This reaction normally happens as a result of an infection or trauma.

Hyperpyrexia differs from hyperthermia, a medical term for the uncontrolled rise in body temperature due to excess amounts of body heat generated.

In hyperthermia, the brain is not regulating the rise in temperature the way it does with other fevers. Rather, the body cannot handle the heat from environmental causes, and so it overheats.

Cases of heat stroke are due to hyperthermia, and not to hyperpyrexia.

Usually, instances of hyperpyrexia are associated with viral or bacterial infections. Some other causes include the following:

Intracranial hemorrhage

In some cases, bleeding in the brain known as intracranial hemorrhage causes hyperpyrexia. Accidents or other traumas and strokes are the most likely cause of intracranial hemorrhage. The bleeding in the brain can affect an area of the brain called the hypothalamus, which is responsible for regulating the body’s temperature.


In rare cases, hyperpyrexia may result from sepsis. Sepsis is a potentially life-threatening response to an infection caused by the immune system. The overwhelming immune system response gets into the blood, which may cause organ damage or failure.


People may experience hyperpyrexia due to a direct side effect of general anesthesia, occurring when there is an underlying disease of muscle. In these cases, a person’s temperature rises rapidly while under anesthesia, requiring doctors to make adjustments to lower the body’s temperature again.

Hyperpyrexia in children

Kawasaki syndrome or disease is a potential cause of hyperpyrexia, especially in children. Kawasaki syndrome causes inflammation to the medium-sized arteries throughout the body. One sign of Kawasaki disease is high fever, which can result in hyperpyrexia if left untreated.

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Headaches can be a sign that a fever is becoming more severe.

Symptoms of hyperpyrexia vary from person to person, depending on how long the condition lasts and if it worsens. Early symptoms may include:

  • increased thirst
  • extreme sweating
  • dizziness
  • muscle cramps
  • fatigue and weakness
  • nausea
  • light-headedness

As the high temperature persists or gets worse, the severity of the symptoms can increase. This situation can lead to:

  • headache
  • contracted pupils
  • mild confusion
  • pale, moist, and cool skin
  • vomiting or upset stomach
  • decreased urination or inability to urinate

In prolonged periods of a temperature of more than 106.1°F, the following symptoms may occur:

  • extreme confusion
  • loss of consciousness
  • rapid, shallow breathing
  • dry, hot, and red skin
  • weak, fast pulse
  • widened pupils
  • seizures

It is essential to seek treatment for fevers over 106.1°F to help prevent serious long-term complications or death.

As hyperpyrexia is caused by another disease, treating the latter will usually cause the body’s temperature to go down.

When the body temperature starts reaching 106.1°F and higher, it may be necessary to treat the fever itself, as well as the underlying cause. Direct treatment of hyperpyrexia may include:

  • a cool bath or cold, wet sponges put on the skin
  • liquid hydration through IV or from drinking
  • fever-reducing medications, such as dantrolene

In cases of malignant hyperpyrexia caused from general anesthesia, doctors will need to take steps to reduce the patient’s fever.

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A thermometer is used to diagnose hyperpyrexia.

Diagnosing hyperpyrexia is done using a thermometer. If the reading is over 106.1°F, then the person has the symptoms of hyperpyrexia.

Since hyperpyrexia itself is not a diagnosis and only a symptom of a larger problem, finding the underlying cause of the high fever is more important and often more challenging.

A doctor will assess the person’s physical state and run tests to rule out the more common causes of high fever. These test may include the following:

  • blood work, to check for signs of infection
  • image studies of the brain to check for intracranial hemorrhage

Further tests will largely depend on any other symptoms the person has.

If the fever is not treated and a person’s temperature brought down to a safe level, hyperpyrexia can cause permanent brain damage or death.

However, in most circumstances, correct treatments can lower the fever safely, giving doctors time to diagnose and treat the underlying cause of the hyperpyrexia.