Fever

Fever, or pyrexia, is the elevation of an individual's core body temperature above a 'set point' regulated by the body's thermoregulatory center in the hypothalamus.

Causes

A fever is not usually a problem in itself, but a symptom of another condition. It indicates that there is something wrong with some part of the body. It can happen when something goes wrong with one of a wide range of functions. The febrile response is orchestrated by the central nervous system through endocrine, neurological, immunological, and behavioral mechanisms.

Infections are the most common cause of fever. Infectious diseases such as influenza, the common cold, HIV, malaria, and gastroenteritis can raise the body temperature. Legal and illegal drugs, including antibiotics, amphetamines, and cocaine can also raise the body temperature.

Other causes of fever are trauma or injury, such as a heart attack, stroke, heatstroke, heat exhaustion, or burns, damage to tissue, surgery, heart attack, hemorrhage, skin inflammation, arthritis, hyperthyroidism, some cancers, lupus, inflammatory bowel disease, blood clots, metabolic disorder, gout, and embolisms.

Antibiotics, narcotics, barbiturates, and antihistamines can cause “drug fevers” due to adverse reactions, withdrawal, or because of the design of the drug.

Function

A fever can help the body fight infection because it increases the amount of antiviral and anticancer interferon in the blood. This makes it difficult for bacteria and viruses to replicate. Body temperature can also help measure the success of medical treatments.

The Concept of Fever

The normal temperature of the human body is approximately 37 degrees Celsius (C) and varies by about 0.5 C throughout the day. This variation in the core body temperature results from normal physiological processes throughout the human body, including metabolic changes, sleep/wake cycles, hormone variability, and changing activity levels. However, in the case of a fever, the increase in the core body temperature is often greater than 0.5 C and is attributed to a fever-inducing substance (pyrogen).

While these numbers may vary slightly based on the source, below is a summary of how to categorize fever.

Low grade: 37.3 to 38.0 C

Moderate grade: 38.1 to 39.0 C

High grade: 39.1 to 41 C

Hyperthermia: Greater than 41 C

The site of measurement influences body temperature readings. The average axillary temperature reading is 35.97 degrees C, oral is 36.57 degrees C, urine is 36.61 degrees C, tympanic is 36.64 degrees C, and rectal is 37.04 degrees C.

While patients can state they have a fever because they "feel warm," the diagnosis of fever based on palpation is unreliable and inaccurate in up to 40% of individuals. If a fever is suspected, an official reading should be obtained.

Types

Fevers can be classified in different ways. One way is the length of time. A fever can be acute, lasting less than 7 days, as in a viral upper respiratory tract infection, sub-acute, lasting up to 14 days, as, for example, in typhoid, chronic or persistent, lasting over 14 days, as in tuberculosis.

They can also be classed according to severity as low grade, moderate, high and hyperpyrexia. The height of the temperature may help indicate what type of problem is causing it.

Fevers can also be:

sustained or continuous, where it does not fluctuate more than 1°C over 24 hours, but is never normal at this time

intermittent, when the fever occurs for several hours in the day, but not all the time

remittent, when it fluctuates by more than 2°C but does not become normal

Typhoid may underlie a sustained fever, tuberculosis tends to cause an intermittent fever and infective endocarditis may trigger a remittent fever. Fevers that exist for days or weeks with no explanation are called fevers of undetermined origin or fever of unknown origin (FUO).

Symptoms

A fever is a symptom, but it can occur with its own symptoms and with other symptoms. A person who has a fever may also have a high temperature, shivering, chills, and shaking, intermittent or excessive sweating, skin flushing, palpitations, feeling weak, dizzy, or faint.

Psychogenic Fever

Psychogenic fever is a condition characterized by an increase in body temperature that emerges after an emotional or high-stress situation. Many patients report intense heat, excessive sweating, headache, and fatigue with this type of fever. It is often triggered by anxiety, mental disorders, and physical conditions like fibromyalgia. It is sometimes referred to as stress-induced hyperthermia.

Psychogenic fever is a common psychosomatic disease. Recently, great advances have been made in the neural mechanisms responsible for stress-induced hyperthermia. Other typical causes of fever, like infection or illness, must be ruled out. Either the brain increases the temperature in response to stress, or stress hormones interact with the endocrine system and lead to an increase in body temperature.

The COVID-19 pandemic has brought more attention to high body temperature without any inflammatory causes as well, which includes psychogenic fever.

In some people, chronic stress causes a persistent low-grade fever of 37 to 38°C. Other people experience a spike in body temperature that can reach as high as 41°C when they’re exposed to an emotional event. Psychogenic fever can happen to anyone under stress, but it most commonly affects young women. Children may experience psychogenic fever with changes to routine, for example. Most psychogenic fevers are short-lived and resolve on their own.

Prevention

If you are experiencing a psychogenic fever, you’ll need to work to reduce your stress levels. Fever as a result of an infectious condition can be dramatically reduced in different ways.

Regular handwashing before eating, after petting animals, or after using the toilet is vitally important when it comes to viral and bacterial infections. Handwashing throughout the day in between using public transportation or touching various surfaces is also a good idea, especially if you are around someone who is unwell.

If you are around someone who is unwell with an infectious condition, it is a good idea to be mindful of touching your nose, mouth, or eyes. If you, yourself are down with an infection, you can be mindful of spreading it when you cough or sneeze. You can also be mindful of sharing eating utensils, hygiene products, towels, clothing, water bottles, or cups.

Ensuring that you are immune to various diseases or infectious conditions can also go a long way in preventing fevers, which can be complex or become serious. If you are traveling, appropriate vaccinations and preventative medications will help reduce any risk.