Occult Bacteremia
Occult (hidden) bacteremia is the presence of bacteria in the bloodstream of a child who has a fever but who may not appear particularly sick and who has no apparent other source of infection.
Children younger than 3 years commonly develop fevers. Most of the time, they have other symptoms, such as a cough and runny nose, which allow doctors to diagnose the cause. About one third of the time, children have no other symptoms besides fever. Most of these children have viral infections that go away without treatment. However, 2 to 4% of such children have bacteria circulating in the bloodstream (bacteremia). Streptococcus pneumoniae is the most common type of bacteria causing occult bacteremia. Circulating bacteria are almost never present in older children or adults with fever but no other symptoms. These circulating bacteria may attack various organs and result in serious illnesses, such as pneumonia or meningitis. Although only about 10 to 15% of children with occult bacteremia develop these serious problems, doctors perform blood cultures to identify the bacteria before such problems develop. An elevated white blood cell count indicates a higher risk of bacterial infection; in this case, a doctor may choose to start antibiotics before blood culture results are available.
Because doctors cannot tell with certainty which febrile children have bacteremia, doctors may perform complete blood cell counts and blood cultures on some children younger than 3 years whose temperature is higher than 102° F and who do not have an apparent reason for their fever. Because occult bacteremia is much less common in children older than 3, these children do not require blood cultures.
For children who may have occult bacteremia, doctors reevaluate them in 24 to 48 hours, when culture results are available. Children with positive culture results are given antibiotics by mouth at home if they do not appear very ill. Children who show signs of serious illness are typically given intravenous antibiotics in the hospital. Sometimes doctors treat certain children, such as those with an elevated white blood cell count, with a single injection of an antibiotic, such as ceftriaxone, while awaiting the results of blood cultures.
A new vaccine against Streptococcus pneumoniae, given to infants, will greatly reduce the chance of occult bacteremia in vaccinated children. The Haemophilus influenzae type b vaccine, now given to nearly all children in the United States, has nearly eliminated occult bacteremia due to Haemophilus influenzae type b.
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