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Occult Bacteremia


Geoffrey A. Weinberg

, MD, Golisano Children’s Hospital

Reviewed/Revised Feb 2024
Topic Resources

Occult (hidden) bacteremia is the presence of bacteria in the bloodstream of a child who has a fever but who looks well and has no obvious source of infection.

  • Most commonly, occult bacteremia is caused by Streptococcus pneumoniae bacteria.

  • Typically, children have no symptoms other than fever.

  • The diagnosis is based on blood tests.

  • Antibiotics can eliminate the infection.

  • Vaccination can prevent infection by Streptococcus pneumoniae.

Children 3 months to 3 years of age commonly develop fevers. Most of the time, they have other symptoms, such as a cough and runny nose, which help doctors diagnose the cause of the fever. Sometimes, however, children have fever and no other symptoms. That is, they have a fever with no apparent source or cause. In most of these children, the fever is caused by a viral infection that goes away without treatment. In some children, a urinary tract infection Urinary Tract Infection (UTI) in Children A urinary tract infection is a bacterial infection of the urinary bladder ( cystitis), the kidneys ( pyelonephritis), or both. Urinary tract infections are caused by bacteria. Infants and young... read more is present. In a few children who have fever with no obvious cause, the fever is caused by bacteria circulating in their bloodstream (bacteremia). Circulating bacteria are almost never the cause of fever in older children or adults who have no other symptoms.

In the United States and Europe, vaccination Childhood Vaccination Schedules Vaccination protects children against many infectious diseases. Vaccines contain either noninfectious components of bacteria or viruses or whole forms of these organisms that have been weakened... read more of infants with the Haemophilus influenzae type b conjugate vaccine Haemophilus influenzae Type b Vaccine The Haemophilus influenzae type b (Hib) vaccine helps protect against bacterial infections due to Hib, such as pneumonia and meningitis. These infections may be serious in children. Use... read more and the Streptococcus pneumoniae conjugate vaccine Pneumococcal Vaccine Pneumococcal vaccines help protect against bacterial infections caused by Streptococcus pneumoniae (pneumococci). Pneumococcal infections include ear infections, sinusitis, pneumonia... read more has nearly eliminated occult bacteremia caused by these bacteria in vaccinated children. Vaccines against Neisseria meningitidis Meningococcal Vaccine The meningococcal vaccine protects against infections caused by the bacteria Neisseria meningitidis (meningococci). Meningococcal infections can lead to meningitis (an infection of tissue... read more are given routinely to preadolescents and adolescents and also can be given to certain children under 36 months of age who have an increased risk of infection. Children who have received their recommended vaccines are very unlikely to develop occult bacteremia. However, occult bacteremia can still occur in children who have received no vaccines or not enough doses and in children who have an impaired immune system.

Did You Know...

  • Children who have received their recommended vaccines are very unlikely to develop occult bacteremia.

Symptoms of Occult Bacteremia

The major symptom of occult bacteremia is

  • Fever higher than or equal to 102.2° F (39° C)

Children who have other symptoms, such as cough, shortness of breath, little or no interest in anything (listlessness), or red or blue discoloration of the skin, are not considered to have occult bacteremia. They most likely have a specific bacterial infection and should be evaluated by a health care professional right away.

Diagnosis of Occult Bacteremia

  • Blood culture

  • Urine culture and urinalysis

  • Sometimes other blood and stool tests and a spinal tap

Because doctors cannot tell with certainty which children who have a fever have occult bacteremia, doctors need to identify any bacteria by doing a blood culture. Because the bacteria are too few or too small to see, doctors send samples of blood to the laboratory so the bacteria can be examined and grown (cultured Culture of Microorganisms Infectious diseases are caused by microorganisms, such as bacteria, viruses, fungi, and parasites. Doctors suspect an infection based on the person's symptoms, physical examination results,... read more ) for identification. If the culture results are positive, it means bacteria have been found.

Infants or children of any age who have a fever and who appear seriously ill, regardless of whether they have received vaccinations, have samples of blood, urine, and cerebrospinal fluid (fluid from around the brain and spinal cord) taken for testing. The fluid is removed during a spinal tap Spinal Tap Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Imaging tests commonly used to diagnose nervous system (neurologic) disorders... read more Spinal Tap (lumbar puncture), which involves withdrawing a sample of fluid from the space between 2 vertebrae using a small needle. All samples are sent to a laboratory for testing to look for signs of bacterial infection. In most cases, the infant or child is admitted to the hospital and given antibiotics. Children who have trouble breathing will likely have a chest x-ray as well.

Other blood tests may also be done depending on the age of the child.

Rapid detection tests for certain viruses may also be done in some children. For these tests, a swab is used to take a sample from the nose or throat. The results usually are available within a few hours.

Infants under 3 months of age

As opposed to children 3 months to 3 years of age, when infants under 3 months of age have a fever, doctors cannot always tell just by looking at them whether they could have bacteremia. In these infants, doctors usually do laboratory tests (complete blood count, urinalysis, and blood cultures). If the results of the blood and urine tests seem normal, some doctors have parents or caretakers monitor the infant at home and then return to the doctor's office within 24 hours so the infant can be re-examined and the blood cultures checked. They do not prescribe antibiotics during this time. Other doctors prefer to admit these infants to the hospital and do further tests of the blood, urine, and spinal fluid.

Most doctors consider infants less than 30 days old to be at especially high risk of bacteremia, which has a number of causes. Infants in this age group are typically admitted to the hospital and tests of the blood, urine, and spinal fluid are done. They usually are treated with antibiotics while waiting for results of the laboratory tests.

Infants and children 3 months to 3 years of age

Infants and children in this age group who have a fever but who have complete vaccinations and who appear well are at very low risk of bacteremia. Because of this low risk, doctors may decide to monitor the children without doing blood tests. However, a urinalysis and a urine culture are typically done to look for a urinary tract infection Urine tests A urinary tract infection is a bacterial infection of the urinary bladder ( cystitis), the kidneys ( pyelonephritis), or both. Urinary tract infections are caused by bacteria. Infants and young... read more as a cause of the fever. The parents or caretakers are asked to monitor the children's symptoms and follow up with the doctor (by visit or telephone) in 24 to 48 hours. Children who worsen or whose fever does not go away have blood tests and possibly chest x-rays or a spinal tap.

Treatment of Occult Bacteremia

  • Antibiotics

Sometimes, before results of the cultures are known, doctors give an antibiotic to children who have a fever and who appear seriously ill and who are at high risk of bacteremia. Usually, doctors give an injectable antibiotic such as ceftriaxone.

Children with positive culture results who do not appear very ill are given an injectable antibiotic or antibiotics by mouth at home. Children who have positive culture results and who show signs of serious illness are admitted to the hospital and given antibiotics by vein.

All children who were being observed at home are evaluated again in 24 hours either at a repeat visit or, for certain children depending on their age and other medical circumstances, via telephone. Children who still have fever or who have positive blood or urine cultures and have not been given antibiotics already have more cultures done and are hospitalized. They are then evaluated for serious illness and are given antibiotics by vein.

Children under 3 months of age are often treated with antibiotics such as ceftriaxone, cefotaxime, or cefepime while waiting for results of laboratory tests.

Children 3 months to 3 years of age may be given medications, such as acetaminophen, that lower body temperature and make them feel better.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Ceftrisol Plus, Rocephin
7T Gummy ES, Acephen, Aceta, Actamin, Adult Pain Relief, Anacin Aspirin Free, Aphen, Apra, Children's Acetaminophen, Children's Pain & Fever , Children's Pain Relief, Comtrex Sore Throat Relief, ED-APAP, ElixSure Fever/Pain, Feverall, Genapap, Genebs, Goody's Back & Body Pain, Infantaire, Infants' Acetaminophen, LIQUID PAIN RELIEF, Little Fevers, Little Remedies Infant Fever + Pain Reliever, Mapap, Mapap Arthritis Pain, Mapap Infants, Mapap Junior, M-PAP, Nortemp, Ofirmev, Pain & Fever , Pain and Fever , PAIN RELIEF , PAIN RELIEF Extra Strength, Panadol, PediaCare Children's Fever Reducer/Pain Reliever, PediaCare Children's Smooth Metls Fever Reducer/Pain Reliever, PediaCare Infant's Fever Reducer/Pain Reliever, Pediaphen, PHARBETOL, Plus PHARMA, Q-Pap, Q-Pap Extra Strength, Silapap, Triaminic Fever Reducer and Pain Reliever, Triaminic Infant Fever Reducer and Pain Reliever, Tylenol, Tylenol 8 Hour, Tylenol 8 Hour Arthritis Pain, Tylenol 8 Hour Muscle Aches & Pain, Tylenol Arthritis Pain, Tylenol Children's, Tylenol Children's Pain+Fever, Tylenol CrushableTablet, Tylenol Extra Strength, Tylenol Infants', Tylenol Infants Pain + Fever, Tylenol Junior Strength, Tylenol Pain + Fever, Tylenol Regular Strength, Tylenol Sore Throat, XS No Aspirin, XS Pain Reliever
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