Summary: Fever usually indicates the presence of inflammation in the body. Fever is usually due to an infection; most commonly a virus infection such as a cold or a flu. However, the causes of fever are numerous and some of these causes are serious. Diagnosing these conditions is very difficult. Most fevers are caused by minor illnesses, but accurately distinguishing serious causes of fever from minor causes of fever is very difficult. If your child has a fever, you should ideally discuss this with your child's physician or have your child seen by a physician. Even after a physician's exam checks out OK, there may be hidden (occult) potentially serious causes of fever that cannot be detected early on without laboratory tests.
Fever is a response by the body to a disease process that causes reaction by the body's immune system. Although there are many causes of fever, by far the most common cause of fever is infection. Fever is not a disease. Rather, fever is a symptom (a clue) that there is a disease process in the body, which is almost always an infection. When your child has a fever, the most important issue here is not the fever itself, but finding out the cause of the fever. A complete listing is impossible, but look at some causes of fever below:
Some causes of fever (examples):
. . . . A. Infections
. . . . . . . . 1. Minor infections
. . . . . . . . . . . . a. Colds (virus)
. . . . . . . . . . . . b. Flu (virus)
. . . . . . . . . . . . c. Tonsillitis (virus, strep throat, etc.)
. . . . . . . . 2. More serious infections
. . . . . . . . . . . . a. Pneumonia (infection in the lungs)
. . . . . . . . . . . . b. Cellulitis (infection of the soft tissues underneath the skin)
. . . . . . . . . . . . c. Osteomyelitis (infection in the bones)
. . . . . . . . . . . . d. Viral meningitis (viral infection in the area around the outside of the brain)
. . . . . . . . 3. Very serious infections
. . . . . . . . . . . . a. Bacterial meningitis (bacterial infection invading the brain)
. . . . . . . . . . . . b. Toxic shock (infection that produces toxin circulating in the blood stream)
. . . . . . . . . . . . c. Sepsis (overwhelming infection involving the blood and other body organs)
. . . . B. Other types of inflammatory disease
. . . . . . . . 1. Lupus
. . . . . . . . 2. Rheumatoid arthritis
. . . . . . . . 3. Appendicitis
. . . . C. Malignancies (cancers)
. . . . . . . . 1. Leukemia
. . . . . . . . 2. Lymphoma
. . . . . . . . 3. Other cancers
. . . . D. Other causes not involving the immune system
. . . . . . . . 1. Heat stroke
. . . . . . . . 2. Defect in the temperature regulation center of the brain
From this brief list, you can see that the causes of fever can be minor (colds, flu, etc.) or they can be very serious and life-threatening. Fever is one of the most common causes for children to visit their doctor. Is there a simple way to distinguish minor causes of fever from serious causes of fever? The answer is somewhat yes and somewhat no. Most fever illnesses can be determined to be minor with a few simple things to check; however, to be more certain, a physician would have to find out more details about the illness, examine your child fully and possibly perform some laboratory tests. This is rather difficult. Do you believe that every time your child has a fever, you should see a physician immediately? It depends on how much certainty you want. Total certainty is not possible. Less certainty can be achieved with parental judgment. More certainty requires frequent visits to the doctor.
Many parents ask what temperature is dangerous? Is there a temperature level that requires immediate medical attention? Temperatures in excess of 104 degrees F (40 degrees C) are more concerning than lower temperatures, but the height of the fever does NOT help much in identifying a serious infection. Most of the time, high fevers are due to minor infections such as viral flu-like illnesses. A more helpful way to distinguish a minor infection from a more serious one, is to base this distinction on your child's general appearance. Lethargy and irritability are potentially bad signs. A child with a temperature of 104 degrees F (40 degrees C) who is happily playing video games, is not very likely to have a serious infection. A lethargic child can be characterized as one who doesn't look at you well (doesn't focus), or who is poorly responsive, or who is not very interactive with things around them. An irritable child is one who is very fussy and does not calm down when you carry or comfort him/her. A lethargic or irritable child with a temperature of 100.5 degrees F (38 degrees C) is more worrisome than an active and alert child with a high fever.
Controlling fever is covered in more detail in the next chapter. Does a prompt reduction in temperature with fever control measures indicate the presence of a minor infection? Not definitely. While prompt fever reduction following a dose of fever medication is comforting, this does NOT confirm that the illness is minor since the fever in many serious infections may respond well to fever control measures.
By carefully assessing your child's general appearance and level of activity, you will be able to identify most serious conditions. But many conditions are difficult to identify early on. A complete assessment checklist is beyond the scope of this chapter. The best advice I can give you is to CALL YOUR DOCTOR TO DISCUSS YOUR CHILD'S CONDITION BY PHONE or SEE YOUR DOCTOR IN THE OFFICE. If you cannot reach your physician, then you must decide whether you can wait for your doctor or you should to an emergency room.
Fever in infants under 3 months of age warrants a prompt call to your physician. Fever in children with long-term illnesses which weaken the body's immune system (such as diabetes, sickle cell disease, leukemia, etc.), is potentially more serious and this warrants a prompt call to your physician. These two situations are special since the known risk is higher so the standard evaluation suggestions below do not apply. Rather, the following suggestions apply to healthy children over three months of age.
Some examples of potentially bad symptoms and signs:
These require prompt medical attention. See your doctor right away, call your doctor immediately or seek care in an emergency room.
1. Coughing a lot. This suggests the possibility of pneumonia.
2. Difficulty breathing. This suggests a potentially serious respiratory infection.
3. Swollen parts of the body. This suggests infection or inflammation.
4. Headache and/or neck discomfort. While this is most commonly due to minor infections such as the flu or sinusitis, more severe headaches are often seen with brain infections.
5. Vomiting. While this is most commonly due to minor infections such as the flu, this can also be seen with kidney infections, brain infections, appendicitis, heart failure, and many other potentially serious conditions.
6. Abdominal pain. Most children with abdominal pain do not have serious conditions, but sometimes, they have conditions such as appendicitis or twisted internal organs.
7. Unusual rashes or spots that you have never seen before or a rash that worsens quickly. Most rashes are not serious, but some are very serious. It would not be possible to describe all the possibilities in a brief paragraph. If the rash is unusual or dramatic, it should be evaluated by a doctor.
8. Any fever in an infant less than three months of age is potentially serious.
Very bad symptoms and signs:
These require immediate medical attention, usually in an emergency room.
1. Lethargy. This suggests that the brain is not working properly, possibly due to poor nutrient or blood flow to the brain. This is serious.
2. Irritability. This suggests the presence of pain or discomfort. Irritability is associated with severe infections such as meningitis (brain infection), sepsis (overwhelming body infection) and others.
3. Poor color (pale, gray or blue). This suggests that blood is not circulating well or the body's oxygen level is low.
4. Weakness. This suggests that the body is not circulating blood well or the infection is overwhelming.
Last of all, there is the problem that even after a doctor's examination, hidden serious infections may be present. These conditions are called "occult", because it is not possible to detect these conditions early without the use of laboratory testing or special imaging technologies. Two of the most common examples of this are bacteremia and urinary tract infections in small children. Infections in the heart and small pneumonias may also be difficult to identify.
Bacteremia is a condition where bacteria are circulating in the child's bloodstream. It is estimated that about 4% of young children who have high fevers (greater than 102.2 F or 39 C) without infections detected elsewhere on examination, have bacteremia. In the other 96% of children, the fever is caused by a minor virus infection that the body's immune system clears without difficulty. The only way to find out if a child has bacteremia, is to obtain a blood culture. A blood sample is drawn and this blood sample incubates in the lab to see if any germs grow from the sample. It usually takes one or two days for a blood culture to grow. Thus, bacteremia cannot be identified when the child is being evaluated by the doctor. The test can be ordered, but its result won't be known for 1 to 2 days.
While bacteremia sounds like a serious condition, most children with bacteremia will cure themselves by having their immune system clear the bacteria from the bloodstream. However, some children with bacteremia develop complications because the bacteria can spread infection to any part of the body. For example, bacterial infection could spread into the brain (and cause meningitis), the lungs (and cause pneumonia), the bones (and cause bone infection) and many other possible places in the body. These complications are serious. But since only about 4% of these children with high fever have bacteremia, and only some of them develop these complications, it is estimated that only a few children develop serious complications that result in permanent disability or death. Death and permanent disability are very serious, but this only happens to a few patients. Treating patients with antibiotics early on may prevent these complications. But since only a few patients have complications, it would require that many children be treated with antibiotics unnecessarily to prevent the complication of serious infection in a few. Some doctors believe in ordering a CBC test (complete blood count), which counts the numbers of the different types of cells in the blood, may be helpful. The white blood cell count (WBC) is an indicator of infection in the body, but this is a poor test that is not very accurate at predicting whether bacteremia is present. If the WBC is high, then the risk of bacteremia goes from 4% to a few percentage points higher. If the WBC is low, then the risk of bacteremia drops a few percentage points.
The treatment of fever is very controversial because most children will do well, but a few will suffer severe complications. Here are some possible ways to manage these patients:
. . . . 1. Observation only. Return to the doctor if any serious symptoms or signs develop.
. . . . 2. Antibiotics without any tests.
. . . . 3. Do a CBC. If the WBC is high, then obtain a blood culture and treat with potent antibiotics.
. . . . 4. Do a blood culture and treat with antibiotics.
Choice #1 has the advantage of avoiding the pain and cost of tests, but it will fail to identify patients destined to have complications. This choice has the highest likelihood of permanent disability or death.
Choice #2 has the advantage of reducing the risk of bacteremia's complications by treating with antibiotics, while avoiding the pain and cost of tests. However, many patients would be treated with antibiotics for a full 10 days unnecessarily and many of them would experience the side effects of antibiotics. Most medical experts do not like this choice because this does not identify which patients have bacteremia. Also, when large numbers of patients in a community are treated with antibiotics unnecessarily, the threat of bacterial antibiotic resistance emerges. This means that the bacteria would eventually have to be treated with different antibiotics that aren't as good and have much more side effects.
Choice #3 has the advantage of doing blood cultures and treating only a few patients with antibiotics (those who have a high WBC). But because the CBC is not a perfect test, many of the patients with bacteremia who will have complications, will initially have a normal WBC. These patients would go on to develop complications since they will not be tested for bacteremia (no blood culture done) and they will not have been placed on antibiotics.
Choice #4 is the safest approach. If the blood culture is negative after three days, then the risk of bacteremia is practically eliminated. Antibiotics can be stopped at this time (only 3 days of unnecessary antibiotics compared to 10 days in choice #2). If the blood culture is positive, then the risk of complications is lowered since these patients will have been on antibiotics from the start. However, this choice requires that ALL children with high fever have blood cultures and antibiotics. Most children have several episodes of high fever before they reach age 3 years. Under choice #4, many, many children would have to have blood cultures and antibiotic treatments just for fever, several times before they reach age 3 years. Thus, although choice #4 is the safest, it is also the most costly and the most painful. It may also contribute to the threat of bacterial antibiotic resistance described in choice #2.
Which choice is best? Each choice has its advantages and disadvantages. Since no strategy is universally superior, this decision is very controversial. This should be discussed with your doctor.
For urinary tract infections (infection in the bladder or kidneys), the decision making is simpler. Young children are unable to tell us that it hurts when they urinate. The presence of vomiting and diarrhea may deceive a physician into believing that the fever is caused by a stomach flu. But urinary tract infections frequently cause vomiting and/or diarrhea. Females are at greater risk for urinary tract infection than males. Thus, if a child has a high fever, a urine sample should be obtained in all females under 24 months of age and all males under 6 months of age. Catheterized urine samples are the best urine samples to analyze for infection, but they are uncomfortable for the child. A catheterized urine sample is obtained by passing a small tube (catheter) into the bladder, through the penis in a male or the urethra in a female. When the tube enters the bladder, the urine in the bladder flows out and it is collected in a sterile container. The catheter is then removed. When done by experienced nurses, a catheterized urine sample is safe and quick. Other urine collection methods may be satisfactory at identifying a urinary tract infection. This should be discussed with your doctor.
Infection in the lung is called pneumonia. Small pneumonias may be difficult to hear with a stethoscope. Most children with pneumonia are coughing a lot, but not always. In children with a small pneumonia who are not coughing much, it may be very difficult for the doctor to identify a pneumonia. A chest X-ray may help to identify a small pneumonia, but the doctor has to suspect a pneumonia to order an X-ray in the first place.
Infections in the heart are rare, but very serious. Infection of the valves, the heart muscle, or the covering of the heart may cause the heart to pump blood poorly to the body. These conditions are very difficult to identify in children. An X-ray of the chest may see some of these conditions, but the condition must be suspected for an X-ray to be ordered. An echocardiogram (an ultrasound test which images the function of the heart as it pumps) is the best test to identify these conditions, but it is not a routine test. One of the conditions must be suspected based on the history and exam for the echocardiogram to be ordered. The early symptoms of infections in the heart are fever, vomiting and chest pain. Small children cannot tell us if they have chest pain. Parents will probably only notice the fever and vomiting. It will be difficult for a doctor to hear the subtle sounds of a heart infection if a child is crying, which is frequently the case. This makes it difficult to identify infections in the heart.