Fever - Symptoms, Types, Causes & Diagnosis

Fever - Symptoms, Types, Causes & Diagnosis

A fever is defined as an elevated body temperature that is above the normal temperature. A high fever, also known as hyperthermia or pyrexia, is typically a symptom that your body is attempting to protect you from an...

What is Fever?

A fever is defined as an elevated body temperature that is above the normal temperature. A high fever, also known as hyperthermia or pyrexia, is typically a symptom that your body is attempting to protect you from an infection. Everybody's normal body temperatures vary, but they fall between 97 and 99 degrees.

Body temperature is regulated by the hypothalamus. The hypothalamus has the ability to reset the body temperature to a greater level in reaction to an infection, illness, or another trigger.

This rise in the body's "fixed" temperature is frequently caused by a physiological reaction to infectious or non-infectious factors such inflammation, cancer, or autoimmune processes. These mechanisms entail the release of immunological mediators, which activate the hypothalamic thermoregulatory center and raise body temperature.


Fever based on duration:

  • Under seven days, it is considered acute.
  • If it lasts up to 14 days, it is subacute.
  • If it occurs for more than 14 days, it is chronic.

Fevers of unknown origin are those that last for days or weeks without a known cause.

Fever Symptoms

you can also experience the following signs:

  • Shivering or chills
  • Sweating
  • Headache
  • Feel weak
  • Having a bad mood
  • Losing interest in food
  • Being thirsty


A balance between heat generation and heat loss determines the average body temperature. This balance is controlled by the hypothalamus, it is also referred to as the "thermostat" of your body.

The hypothalamus has the power to boost body temperature in reaction to disease. It begins a complex process that leads to increase in heat production and a reduction in heat loss. By wrapping in a blanket you help the body to retain heat.

Low-grade viral infections are linked to fever under 104 F (40 C).

Other factors include:

  • Infections of the kidney, bladder, skin, ear, lung, or throat
  • A heat stroke
  • COVID-19
  • Sunburn
  • Inflammation-causing conditions, like rheumatoid arthritis
  • Adverse drug reactions
  • Immunizations and vaccinations
  • Clots of blood
  • Inflammatory bowel disease and lupus are examples of autoimmune diseases (IBS)
  • Cancer abnormalities of the hormones, such as hyperthyroidism
  • illegal substances like cocaine and amphetamines Infants who are teething may experience a slight, low-grade fever.

COVID-19 signs

A person may experience COVID-19 symptoms if they have a dry cough and a fever.

People who experience these symptoms are advised by the Centers for Disease Control and Prevention (CDC)Trusted Source to remain at home and avoid social situations.

The symptoms frequently get better on their own without medical attention.

But if the person also experiences excruciating chest discomfort or has trouble breathing.

Types of Fever

Continuous fever

In conditions such as bacterial pneumonia, typhoid, infective endocarditis, tuberculosis, or typhus, a continuous fever is one in which the body's temperature remains above normal and does not change by more than 1 degree in a day.

Intermittent fever: when fever only lasts a short while before returning to normal, as in the cases of malaria, leishmaniasis, pyemia, sepsis, or African trypanosomiasis.

Remittent fever: It is a condition when the temperature fluctuates by more than one degree in a 24-hour period while remaining above normal throughout the day. (e.g., in infective endocarditis or brucellosis) (e.g., in infective endocarditis or brucellosis).

Cyclic fever: Patients with Hodgkin's lymphoma infrequently experience Pel-Ebstein fever, a cyclic fever.

Undulant fever: A brucellosis symptom.

Typhoid fever: It is a persistent fever with a recognizable step-ladder pattern or a stepped rise in temperature followed by a high plateau.

Among the varieties of intermittent fever are several that are exclusive to malaria cases brought on by certain infections. Which are:

Quotidian fever: which occurs in a 24-hour cycle and is a sign of Plasmodium knowlesi malaria;

Tertian fever: with a 48-hour periodicity, typical of late-stage malaria caused by Plasmodium falciparum, Plasmodium vivax, or Plasmodium ovale;

Quartan fever: with a 72-hour periodicity, typical of late-stage malaria caused by Plasmodium malariae.


Hyperpyrexia is defined as a core body temperature that is higher than or equivalent to 40 or 41 °C (104 or 106 °F); the range of hyperpyrexia includes cases that are termed severe ( 40 °C) and extreme ( 42 °C).

It differs from hyperthermia in that the body temperature set point of the thermoregulatory system is elevated and subsequently heated to reach it. Contrarily, hyperthermia occurs when the body's temperature rises above its normal range as a result of external stimuli. [7][60] Since hyperpyrexia's high temperatures might signal a significant underlying ailment, cause severe morbidity (including lifelong brain damage), or even cause death, they are regarded as medical emergencies.

A haemorrhage inside the skull is a frequent cause of hyperpyrexia. Sepsis, Kawasaki disease, neuroleptic malignant syndrome, medication overdose, serotonin syndrome, and thyroid storm are among more causes that might occur in emergency rooms.


The complicated interactions between peripheral cells that lead to the onset of fever are subsequently relayed centrally to the hypothalamus, more specifically to the ventral medial preoptic (VMPO) region. Several investigations revealed that the blood-brain barrier-deficient vascular organ of lamina terminalis (VOLT), which is located close to the VMPO, is where fever-activated neurons are found (BBB). Due to the absence of a BBB, circulating chemicals, including immune system components linked to fever, can enter the brain.


The fever response, which has been around for more than 600 million years in warm-blooded species, is a systemic response to an illness. It is well established that raising core body temperature enhances survival and clears illnesses. It is well recognized that the survival advantages outweigh the metabolic cost connected with a fever, even when a raised body temperature subsequently results in an increased metabolic cost. The body's core temperature rising signals many cell types, including natural killer cells, macrophages, dendritic cells, T and B lymphocytes, vascular endothelial cells and neutrophils to begin immunological surveillance.

A Temperature Reading

  • You can take your temperature with a number of thermometers, including oral, rectal, ear, and forehead (temporal artery) thermometers.
  • The most accurate tools for recording body temperature are oral and rectal.
  • For neonates, a rectal temperature reading is a little more accurate. When reporting a temperature, let your doctor know both the reading and the manufacturer of the thermometer.
  • Nowadays, the majority of people take their temperature with a digital thermometer. Glass thermometers are risky, so experts advise against using them. The accuracy of a forehead strip varies depending on the user.
  • A thermometer can be inserted in the mouth or under the arm.

Using a Digital Gadget

  • Rinse the tip after cleaning it with cold water and soap. Activate the device.
  • Put the thermometer into your mouth
  • Alternately, hold the gadget near the body and position it under the armpit.
  • Wait for the thermometer beep or there is a flash.
  •  Read the thermometer.
  • When the temperature is at or higher than one of these thresholds, a child has a fever.

Referral values for measuring body temperature by different means

The lowest temperature was 100.4°F (38°C) (rectally) When measured in the mouth, 99.5°F (37.5°C) (orally) 99°F (37.2°C) beneath the arm, measured (axillary) An adult most likely has a fever

if their temperature is over 99°F to 99.5°F, depending on the time of day.

When to Seek Medical Attention

In and of itself, a fever might not be a cause for alarm or a visit to the doctor. There are, however, some circumstances in which you should seek medical attention for you, your kid, or your new baby.

Infants and Toddlers

  • A fever is concerning in infants and young children.
  • if your child has atleast 100.4 F rectal temperature and is under three months old (38 C).
  • between the ages of 3 and 6 months, with a rectal temperature of 102 F or below but being oddly irritable,irritable, drowsy, or uneasy.
  • between the ages of seven and twenty four months, a rectal temperature of 102 F or higher that lasts more than a day without any other symptoms.

You can contact sooner if your child also exhibits additional symptoms, such as a runny nose, cough, or diarrhoea.


  • There is usually nothing to be concerned about if your youngster starts to feel warm but is otherwise aware. This shows that your child responds to your speech and facial expressions while also looking you in the eye.
  • Your kid may be playing and drinking fluids at the same time.
  • If your child lacks good eye contact, is perplexed, or seems listless, call their doctor straight away. is agitated, regularly pukes, has a strong headache, sore throat, stomachache, or other severely painful symptoms.
  • fever for more than three consecutive days.
  • has a fever and a seizure both together.
  • If the seizure continues for longer than five minutes or your call 911 If your child's seizure lasts longer than five minutes or doesn't end immediately.
  • Ask your child's doctor for advice if there are any unusual circumstances, such as a youngster with immune system problems or a history of illness.


  • In the event that your temperature is 103 F (39.4 C) or above, get in contact with your healthcare provider.
  •  If any of these cautionary indicators or symptoms co-occur with a fever, seek medical attention right away.
  • awful headache
  • Neck ache
  • extraordinary sensitivity to bright light
  • Pain in neck and stiffness when bending your head forward
  • perplexity in the mind, odd conduct, or altered speech
  • continual vomiting
  • breathing issues or chest pain
  • Continent pain
  • difficulty urinating
  • seizures or tremors


These are some diagnostic procedures for fever or hyperthermia:

Diagnostic Evaluation

  • CRP and ESR
  • Some bacterial infections cause an increase in procalcitonin.
  • skin test for tuberculosis
  • HIVs Serum
  • LDH
  • standard blood cultures
  • RF, ANA, and heterophile antibodies in kids and teens
  • CPK
  • Electrophoresis of serum proteins
  • study of historical images
  • Lumbar puncture should be initiated by CNS symptoms.
  • Thin and thick peripheral smear examinations should be performed on patients who have visited areas where malaria is common.
  • Eliminate IV drug misuse to rule out thrombophlebitis and infectious endocarditis.

Fever Control

Fever is typically accompanied by physical discomfort, and most people feel better after receiving treatment for their fever. Several scientists believe that fever is the natural defence of the body against sickness. Fever can be due to several non-infectious causes.

The right course of treatment depends on the cause of the fever. If it is due to bacterial infection, such as strep throat then antibiotics are prescribed.

The most common treatments for fever are nonsteroidal anti-inflammatory drugs (Examples of NSAIDS are ibuprofen and naproxen) and acetaminophen. Because Reye's syndrome has been linked to aspirin use, it is not recommended for children or adolescents.


When they have a fever, kids between the ages of six months and five are more prone to have seizures (febrile seizure). After having one febrile seizure, one-third of children go on to have another, generally within the following year.

Body rigidity, rolling eyelids, unconsciousness, and limb tremor on both sides of the body are all possible symptoms of a febrile seizure. While alarming for parents, the majority of febrile seizures have no long-term effects.

When a seizure happens:

  • Put your child on the ground or floor
  • their stomach or side should be up.
  • Take away any sharp things from your child's vicinity.
  • Taking off tight garments
  • Hold your youngster to avoid harm.
  • Never put anything in your child's mouth.


  • you might be able to avoid getting fevers by limiting your exposure to infectious diseases.
  • The following advice may be helpful:
  • Obtain the necessary vaccinations against infectious diseases including COVID-19 and influenza.
  • Observe the public health recommendations for mask use and social isolation.
  • Wash your hands frequently.
  • Teach your kids the proper method of hand washing technique.
  • In situations where you don't have soap and water, sanitizers can be used.
  • Avoid touching your lips, nose, or eyes because bacteria and viruses can infect you by entering your body.
  • cover your mouth while sneezing or coughing.
  • cough or sneeze into your elbow to prevent others from getting infected.
  • Keep your youngster or children from sharing utensils, water bottles, or cups.