Fever and Infection

An abnormally high body temperature is known as fever. It is the body’s natural response to infection. An infection-related fever may be particularly dangerous when your white blood cell count is low or is expected to be low. This occurs when the body’s normal defenses against infection are low. Under these conditions, a fever needs to be carefully monitored and evaluated to find the cause as quickly as possible.

The average human body temperature is 98.6º F (37º C). However, each individual is different, and normal may range from 97º F to 99º F. Also, the human body temperature varies throughout the day. It is lower in the morning and higher in the late afternoon and evening.

Fever is the body’s natural response to infection. The viruses that cause colds and other respiratory infections, for example, thrive at cool temperatures. One way the body works to eliminate these is by producing a fever. A part of the brain called the hypothalamus raises the body temperature to create an environment that is unfavorable for the bacteria or viruses that cause infectious disease.

How is a fever diagnosed?

A fever is confirmed with three oral temperatures greater than 100.4º F (38º C) recorded in a 24-hour period, or with one oral temperature greater than 101.3º F (38.5º C). A severe fever is an oral temperature of 102º F or a rectal temperature of 103º F.

If the fever is infection-related, several tests may be carried out to determine the source of the infection. Samples of blood, urine, tissue from the throat, or drainage from a wound or catheter may be taken and grown in a laboratory culture. If an infection is present in one of these samples, the bacteria will replicate to a degree that can be detected and identified by laboratory procedures.

What are the signs and symptoms of a fever?

Depending on what is causing your fever, your signs and symptoms may include:

• Sweating
• Shivering
• Headache
• Muscle aches
• Lack of appetite
• Dehydration
• General weakness

Very high fevers, between 103º F and 106º F, may cause hallucinations, confusion, irritability, and even convulsions.

Why is a fever important in a cancer patient?

Fever may be a sign of a dangerous infection. An infection may be particularly serious when your white blood cell count is low or is expected to be low. This is because white blood cells are the body’s normal defenses against infection. When their numbers are low, the body’s ability to fight infection is reduced.

In addition, many cancer patients develop a fever in which a definite source of infection cannot be found. Fever is a side effect of some biologic therapies and may occur as part of the “flu-like syndrome” in patients who are receiving chemotherapy and biologic therapy. A fever associated with a flu-like syndrome usually peaks at 104º F (40º C) and often spikes after a severe chill.

For more information on fevers and infection click here.

How is a fever treated?

Medical treatment for a fever depends on the cause. If it is related to an infection, treatment will be prescribed for the infection. For a bacterial infection, such as pneumonia or tonsillitis, antibiotics are usually prescribed. For viral infections, including stomach flu (gastroenteritis), the best treatment is often rest and plenty of fluids, although antiviral drugs may be used to treat some viruses.

If an infection-related fever is tolerable, then doctors may not treat the infection but just monitor it closely because the fever helps eliminate the bacteria or virus. If a cancer patient develops a low white blood count and fever, it is assumed that an infection is present. Antibiotics are given until the fever is resolved and the white blood cell count has recovered.

If an infection-related fever is very high, over-the-counter medications may be prescribed to reduce the fever and associated discomfort. Nonsteroidal antiinflammatory drugs (NSAIDs), such as Tylenol® (acetaminophen), or Advil®, and Motrin® (ibuprofen) are often used for this purpose. Adults may also use aspirin to reduce a fever. However, children should not take aspirin because it may cause a rare but potentially fatal disorder known as Reye’s syndrome.

If you have a bleeding disorder or low platelet count, you should avoid NSAIDs and aspirin. These drugs may prolong bleeding by interfering with the activity of blood platelets. Use of such drugs to treat fever should be discussed first with your health care professional.

Aspirin or NSAIDs are also used if the source of the fever is related to flu-like syndrome associated with biologic therapy or certain types of chemotherapy, and not infection.