Normal body temperature is 98.6 degrees Fahrenheit (37 degrees centigrade) when taken with an oral thermometer. Although there may be slight variations in either direction, a temperature that is more than 1 or 2 degrees higher than usual is considered a fever, and indicates the presence of an infection or another illness. Fevers tend to peak in the late afternoon or early evening. Some diseases are characterized by fevers that appear and disappear during the course of the illness, or that remain high for several days or even weeks. Frequently, the fever is interspersed with chills. Most fevers disappear within 48 hours, but any fever higher than 103 degrees that is accompanied by recurrent shaking or chills, or that lasts for several days, needs medical attention.
Causes of fever and chills
Some forms of arthritis are associated with fever, along with joint swelling and pain and other characteristic symptoms.
A persistent, low-grade fever can be one of the warning signs of cancer. Although many types of cancer can produce fever, it is more common in blood and lymph cancers, and those that have spread to other parts of the body.
These infections are typically accompanied by an earache and fever. Ear infections are particularly common in babies and young children. A low-grade fever accompanied by ear rubbing or obvious discomfort in a baby should be checked by a doctor.
Abdominal pain that is accompanied by fever or other symptoms such as bloating, weakness, sweating, pallor, or bleeding from the mouth or rectum may indicate a gastrointestinal problem. This could range from appendicitis to a host of inflammatory disorders.
Fevers are most frequently a sign of infection, especially in infants and young children. A sudden fever in a healthy child may be a desirable reaction as the body fights off a mild infection. In both children and adults, other symptoms must also be considered to determine the severity of the situation, since a fever-causing infection could be associated with anything from measles to meningitis.
A fever of more than 101 degrees during pregnancy could constitute a medical emergency, especially if it is accompanied by bright red vaginal bleeding and severe abdominal pain. A fever in the second half of pregnancy accompanied by a headache, blurred vision, and swelling of the face and hands indicates possible pre-eclampsia.
This relatively rare disease is seen mostly in children and adolescents. It typically follows a viral infection, such as chickenpox or flu. Aspirin use during a viral illness increases the risk of Reye's. The disease causes brain swelling and severe liver disorders. A fever accompanied by persistent vomiting, irritability, and changes in mental status suggests Reye's syndrome and a need for immediate medical attention.
Toxic shock syndrome
This rare disease usually affects women under age 30. It is caused by a toxin produced by a bacterium that is normally found in the nose and mouth. A sudden onset of fever with vomiting, diarrhea, and perhaps a headache, sore throat, rash, aching muscles, and a severe drop in blood pressure suggests possible toxic shock syndrome.
Overexposure to heat and humidity can lead to heat exhaustion, which is accompanied by a fever of up to 102 degrees, or heatstroke, a medical emergency in which temperatures may rise to 104 degrees or more. Acute sunburn can also cause a low-grade fever.
A low-grade fever accompanied by leg pain indicates possible thrombophlebitis — an inflammation caused by blockage of a vein by a clot. Medical treatment is needed because there is a danger that a part of the clot can break away and travel to the lungs, resulting in a pulmonary embolism, which can be fatal.