Fever in the Infant and Toddler

Introduction

One of the most common problems and greatest challenges faced by those caring for infants and young children is fever. According to guidelines from the Agency of Health Care Policy and Research, in infants younger than 3 months with rectal temperatures 38^o C or higher, the incidence of serious bacterial infection is 6-10%, with a 1-2% incidence of bacteremia, meningitis, or both.¹ In infants aged 3-36 months, the incidence and etiologies of serious bacterial infections among those with rectal temperatures of more than 38^o C has significantly changed following the introduction of effective vaccines for Haemophilus influenzae type b and Streptococcus pneumoniae.^1,2 This article addresses the most common etiologies of fever in these age groups and the appropriate clinical prediction rules for identifying infants and toddlers at lowest risk for serious bacterial infections.

Fever in the Neonate

Neonates with fever who are aged 38 days or younger may have few clues on history and physical examination to guide therapy. Therefore, a high index of suspicion is necessary in order to detect the febrile neonate with a serious bacterial infection. Obtaining the pertinent medical history from the mother regarding the pregnancy, delivery, and early neonatal life of the febrile neonate is essential. Typically, infections that occur in the first week of life are secondary to vertical transmission, and those infections occurring after the first week are usually community acquired or hospital acquired.

Definitive identification of a serious bacterial infection requires laboratory investigation; a full sepsis evaluation; and a positive result in blood culture, cerebrospinal fluid (CSF), and/or urine. Bacterial meningitis is more common in the first month of life than at any other time. An estimated 5-10% of neonates with early onset group B streptococcal sepsis have concurrent meningitis.

Medical History

History of present illness

A thorough history is essential for all neonates with fever. Associated symptoms may be system specific (eg, diarrhea, cough) or nonspecific (eg, poor feeding, irritability, lethargy). Seizures have been reported in 20-50% of neonates with meningitis. Exposures to sick contacts in the household or daycare should be ascertained, as well as a recent history of a previous illness, immunization, or antibiotic use while in the birth hospital or since discharge.

Past medical history

A review of the prenatal history, including maternal history of sexually transmitted infections, maternal group B streptococcus status and prophylaxis, mode of delivery, prolonged rupture of membranes, and history of maternal fever should be noted. A birth weight of less than 2500 grams, rupture of membranes before the onset of labor, septic or traumatic delivery, fetal hypoxia, maternal peripartum infection, and galactosemia are all risk factors for a serious bacterial infection in the neonate. Gestational age should be determined because premature infants are at increased risk for serious bacterial infections.

The neonate’s nursery course should be noted, including the age at which the patient went home from the nursery, whether or not a male neonate has been circumcised, and the use of peripartum or antepartum antibiotics. Any underlying diseases or conditions, as well as the use of medications that may increase the risk of infection, should be ascertained. Diet (ie, quantity and description of milk consumed; breast milk versus formula; and, if pertinent, the method the caregiver uses for preparing and storing the formula) and sleep histories should be obtained because decreased oral intake or an acute change in sleep patterns may be clues to an invasive infection. 

Family medical history

The prenatal history and laboratory evaluation of the mother should be noted (eg, human immunodeficiency virus [HIV], hepatitis B and hepatitis C, syphilis, gonorrhea, chlamydia, and group B streptococcus status). Any ill contacts in the household should also be noted. Exposure to any animals inside the home of the caregiver or outside the home (eg, in daycare facility) should be determined. The vaccination status of household members should be determined. A history of maternal fetal loss or death due to an infectious disease in a previous infant increases the suspicion of congenital anomalies and primary immunodeficiencies.

Social history

Identifying who is in the neonate’s household, who is the primary caregiver, contact with recent immigrants, and exposure to homelessness and poverty all impact the care the neonate receives.
 
Review of systems

A thorough review of systems must be obtained to identify any other symptoms associated with the fever.

Physical Examination

A complete physical examination including vital signs (temperature 38ºC = 100.4ºF), pulse oximetry, and growth parameters with percentiles is necessary. General appearance should be noted for activity level, color, tone, and irritability. Signs of localized infection should be identified via a thorough examination of the skin, mucous membrane, ear, and extremities.

The presence of an umbilical stump after age 4 weeks should be noted because it is a potential clue to leukocyte adhesion deficiency, and the lack of a circumcision in males should be noted because it increases the risk for a urinary tract infection (UTI). In addition to fever, the most common clinical features of a UTI in a neonate include failure to thrive, jaundice (typically secondary to conjugated hyperbilirubinemia from cholestasis), and vomiting. Irritability, inconsolability, poor perfusion, poor tone, decreased activity, and lethargy can be signs of a serious infection in this age group. 

Most neonates with bacterial meningitis have a full fontanelle with normal neck flexion at the time of presentation. Remember that neonates younger than 28 days with significant bacterial infections can appear to be at low risk when analyzing history, physical examination findings, and laboratory values; thus, a high index of suspicion must be maintained.

Laboratory Evaluation and Assessment

A full sepsis evaluation is recommended in all febrile neonates. This includes a CBC count, blood culture, urinalysis, urine culture, and CSF analysis and culture. These patients should be hospitalized with intravenous antibiotics pending results of these cultures. A lumbar puncture for CSF examination is recommended in all neonates younger than 28 days if empiric antibiotics are to be given or if the neonate had a seizure. CSF should be assessed for CBC count and differential, glucose level, protein level, Gram stain, and routine culture. CSF should be assayed for herpes simplex virus (HSV) using polymerase chain reaction (PCR) in all neonates in the first 28 days of life who appear ill, who have mucocutaneous lesions, or who have had a seizure. 

Enterovirus PCR analysis should be performed on the CSF during the summer enteroviral season. Because the incidence of UTIs is high in this age group, a urine specimen should be obtained for urinalysis and urine culture. A negative urine dipstick or urinalysis finding alone does not exclude the diagnosis of a UTI; only a negative urine culture finding can exclude this diagnosis. A urine culture should be obtained via either a suprapubic aspiration or urethral catheterization because bag urine specimens are frequently contaminated.

A chest radiograph should be considered for neonates with signs of respiratory illness such as cough, coryza, tachypnea, rales, rhonchi, retractions, grunting, nasal flaring, or wheezing. During respiratory viral season, an attempt should be made to identify a respiratory viral etiology using direct fluorescent antigen detection or PCR and viral culture on nasal wash specimens.   A stool culture is recommended when blood, mucus, or both are present in the stool; when diarrhea is present; and when more than 5 WBCs per high-power field are noted on methylene blue stain of fresh stool.

Fever in the Young Infant

The general approach to fever in a febrile infant aged 28-60 days includes maintaining a high index of suspicion because these patients often lack clues on physical examination. The prevalence of a serious bacterial infection in an infant younger than 3 months is approximately 6-10%. Interestingly, infants aged 3 months or younger with a confirmed viral infection are at lower risk for a serious bacterial infection when compared with those in whom a viral infection is not identified; although a urinary tract infection (UTI) is still a significant concurrent infection in infants with bronchiolitis.

Medical History

History of present illness

As is the case in neonates, a febrile infant aged 28-60 days may have symptoms that are nonspecific (eg, poor feeding, irritability, lethargy) or specific symptoms (eg, diarrhea, cough). History of exposure to sick contacts in the household or daycare should be obtained, as well as a recent history of a previous illness, immunization, and recent antibiotic use.
           
Past medical history

The past medical history needed is essentially the same as in neonates. A prenatal, perinatal, and neonatal history should be obtained. Underlying diseases or conditions and the use of medications that may increase the risk of infection should be ascertained. In addition, as with neonates, diet and sleep histories should be obtained because decreased oral intake or an acute change in sleep patterns may be clues to an invasive infection. Exposure to any animals inside the home of the caregiver or outside the home such as in the daycare facility should be determined. A travel history of all household contacts should be obtained. The vaccination status of household members should also be determined.
 
Family medical history

As with neonates, a family history of a previous death in a young infant from an infectious disease increases the suspicion of congenital anomalies and primary immunodeficiencies.
           
Social history

As with the neonate, identifying who lives in the household, who is the primary caregiver, exposure to any recent immigrants, and exposure to homelessness and poverty helps establish risk for infection and how to manage the patient.
 
Review of systems

A thorough review of systems must be obtained to identify any other symptoms associated with the fever.

Physical Examination

A complete physical examination including vital signs (temperature 38ºC = 100.4ºF), pulse oximetry, and growth parameters with percentiles is necessary. A heart rate of more than 160 beats per minute in infants and a respiratory rate of more than 60 beats per minute are associated with an increased mortality risk and often signal the development of septic shock.

As with a neonate, general appearance should be noted for activity level, color, tone, and irritability.   Irritability, inconsolability, poor perfusion, poor tone, decreased activity, and lethargy can be signs of a serious infection. Likewise, signs of localized infection should be identified via a thorough examination of the skin, mucous membrane, ear, and extremities. Lack of a circumcision in males should be noted. Unfortunately, bacterial meningitis is often associated with minimal signs and symptoms in this age group and a bulging fontanelle is a late sign. Nuchal rigidity is only present in 27% of infants younger than 6 months.

Laboratory Evaluation and Assessment

In infants older than 28 days, low risk criteria are well defined. The reference range WBC count is 5,000-15,000 cells/μL. The band count should be less than 1500 cells/μL. However, the WBC count alone has poor sensitivity and specificity for identifying young infants with bacteremia and meningitis; thus, the decision to perform a sepsis workup should not be based on the WBC count alone.

Because the incidence of UTIs is still high in this age group, obtain a urine specimen for urinalysis and urine culture. In one study, only 20% of febrile infants with the diagnosis of pyelonephritis had pyuria. A urine culture should be obtained by either a suprapubic aspiration or urethral catheterization because bag urine specimens are frequently contaminated. 

Chest radiography should be considered for infants with signs of respiratory illness, such as cough, coryza, tachypnea, rales, rhonchi, retractions, grunting, nasal flaring, or wheezing. During respiratory viral season, an attempt should be made to identify a respiratory viral etiology using direct fluorescent antigen detection or polymerase chain reaction (PCR) and viral culture on nasal wash specimens. A stool culture is recommended when blood, mucus, or both are present in the stool, when diarrhea is present, and when more than 5 WBCs per high-power field are noted on methylene blue stain of fresh stool.

Although some experts consider a lumbar puncture optional in well-appearing infants with low grade fever who are older than 28 days, a diagnosis of meningitis carries a significant risk of morbidity and mortality, and acceptable risk must be determined for each individual patient.

Various criteria have been developed in an attempt to identify the infant older than 28 days at low risk for a serious bacterial infection. The incidence of a serious bacterial infection in infants categorized as low risk after a full evaluation is small (0.5% in studies that included a lumbar puncture and 1.1% in studies without a lumbar puncture). These studies have led to the development of the Rochester, Boston, and Philadelphia protocols, all of which were conducted in urban emergency departments. The Rochester and Boston criteria exclude patients with ear infections from low risk groups, and the Philadelphia criteria considers low-risk infants those with an "unremarkable physical examination."

Rochester criteria³  

The Rochester criteria are used to assess febrile (temperature >38ºC) infants aged 28-60 days. The risk for occult bacteremia in well-appearing febrile infants is 7-9%; if all Rochester criteria are present, the risk is less than 1%. Infants at high risk were hospitalized with empiric antibiotics, and infants at low risk were discharged with follow-up in 24 hours.

Low-risk criteria include the following:

• Infant must appear generally well
• Infant has been previously healthy
  • Born at term (>37 weeks' gestation)
  • No perinatal antimicrobial therapy
  • No treatment for unexplained hyperbilirubinemia
  • No previous antimicrobial therapy
  • No previous hospitalization
  • No chronic or underlying illness
  • Not hospitalized longer than the mother
• Infant has no evidence of skin, soft tissue, bone, joint, or ear infection
• Infant has the following laboratory values:
  • WBC count of 5,000-15,000/μL
  • Absolute band count of 1,500/μL or less
  • Less than 10 WBCs per high-power field on microscopic examination of the urine
  • Less than 5 WBCs per high-power field on microscopic examination of stool in an infant with diarrhea

Boston criteria

The Boston criteria are used to assess (temperature >38ºC) infants aged 28-89 days. Infants who met the following criteria were managed as outpatients with 50 mg/kg ceftriaxone intramuscularly at the time of discharge. The scheduled follow-up visit was in 24 hours; 5.4% of patients had a serious bacterial infection at follow-up.

The criteria are as follows:

• No immunizations or antimicrobials within the preceding 48 hours
• No evidence of dehydration or ear, soft tissue, or bone infection
• Well appearing
• Caretaker available by telephone
• Infant has the following laboratory values:
  • WBC count less than 20,000/μL
  • Cerebrospinal fluid (CSF) with WBC count less than 10/μL
  • Urinalysis with less than 10 WBC per high-power field on microscopic examination
  • No infiltrate on chest radiograph, if one was obtained

Philadelphia criteria

These criteria was used to assess febrile infants aged 29-60 days with fever (>38.2ºC). All high-risk patients were hospitalized and treated with empiric antibiotics. Low-risk patients were not treated with antibiotics, with follow-up in 24 hours. Sensitivity for identifying patients with a serious bacterial infection was 98%, specificity was 42%, positive predictive value was 14%, and the negative predictive value was 99.7%. 

Low-risk criteria included the following:

• Well appearing
• WBC count of less than 15,000/μL
• Band-neutrophil ratio of less than 0.2
• Urinalysis reveals less than 10 WBC per high-power field on microscopic examination and a negative urine Gram stain result
• CSF has less than 8 WBC/μL and a negative CSF Gram stain finding
• Chest radiograph does not have an infiltrate (if a radiograph was obtained)
• Stool has no blood and few or no WBCs on the smear

Subsequent studies have shown that, when these criteria are applied to the neonatal population (age, 1-28 d), an increased number of infants with serious bacterial illnesses are misidentified as low risk when compared with infants aged 1-3 months. Neonates should be considered high risk and a complete sepsis evaluation should be performed. All febrile neonates should be hospitalized and should receive empiric antibiotic therapy.

The above criteria have not been universally adopted by community practitioners. The importance of reliable follow-up cannot be overstressed if the decision is made not to perform invasive studies in a febrile, well-appearing infant; no guidelines for the minimal evaluation of a febrile, well-appearing infant are recognized. If empiric antibiotics are given, a lumbar puncture should always be performed.

Antimicrobial Treatment

All febrile neonates aged 28-60 days, after having a sepsis evaluation, should be hospitalized and empirically started on intravenous antibiotics pending culture results. The antibiotic spectrum of coverage must include both community-acquired pathogens (eg, S pneumoniae, H influenzae, Moraxella catarrhalis, Neisseria meningitidis, late-onset group B streptococcus, Staphylococcus aureus), perinatally acquired organisms (eg, early onset group B streptococcus, Escherichia coli, and other Gram-negative organisms and Listeria monocytogenes), or hospital-acquired organisms in the neonate or infant who was recently hospitalized (eg, enteric Gram-negative organisms, S aureus).

Ampicillin and gentamicin, or ampicillin and cefotaxime for the neonate, covers group B streptococcus, E coli, Listeria, and most S pneumoniae and N meningitides. For infants aged 1-2 months, recommended empiric coverage includes ampicillin, cefotaxime, and vancomycin to provide adequate coverage for community-acquired pathogens. All antibiotic dosages should be adequate to treat meningitis. For infants older than 2 months, vancomycin and cefotaxime are the empiric antibiotic choices. Vancomycin is especially important if the patient has evidence of soft tissue infection, given the increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA), or a CSF profile consistent with bacterial meningitis to cover for antibiotic-resistant S pneumoniae.

Infants older than 28 days who look well and whose history, physical examination, and laboratory evaluation findings classify them as low risk can be treated as outpatients with ceftriaxone (50 mg/kg in a single intramuscular dose), as long as 24-hour follow-up can be assured.

Acyclovir (60 mg/kg/d divided every 8 h) is recommended for febrile neonates who appear ill, have mucocutaneous vesicles, experience seizures, or have a CSF pleocytosis.⁴ Viral cultures and direct fluorescent antigen detection should be performed on skin vesicles, eyes, and rectal mucous membranes. CSF should be assessed for herpes simplex virus (HSV) and undergo PCR and culture.

Infants older than 28 days who are diagnosed with bronchiolitis or influenza and are relatively well-appearing should undergo a limited laboratory evaluation, including CBC count with differential, blood culture, urinalysis, and urine culture. If the CBC count and urinalysis findings are benign, these patients can be initially managed without antibacterial therapy. Febrile infants younger than 28 days who are diagnosed with a viral respiratory illness should have a septic workup that includes cultures of blood, urine, and CSF and should receive empiric antibacterial therapy in hospital until culture results are known.

Fever in the Child Aged 2 Months to 3 Years

Historically, children aged 3 months to 3 years with rectal temperatures of 38.5^o C or higher had a risk of 2-4% for occult bacteremia.^5,6   The leading cause of bloodstream infection was S pneumoniae, followed by H influenzae type b. With the introduction of effective vaccines for these pathogens, the incidence and epidemiology of childhood bacteremia in the immunologically normal host has changed.  

The incidence of occult bacteremia in this population now ranges from 0.5-1%; moreover, 2 out of every 3 blood isolates from these children represent an artifact (contamination) and not a true pathogen.² S pneumoniae and E coli are the most common pathogens, accounting for two thirds of cases. In infants with S pneumoniae, many isolates are strains not covered by the currently available heptavalent conjugate vaccine. 

Children with pneumococcal bacteremia may present with acute otitis media, pneumonia, symptoms of sinusitis, meningitis, febrile seizures, cellulitis (including orbital or facial cellulitis), or nonspecific febrile illnesses. E coli bacteremia is most common in children younger than 1 year and is usually associated with urinary tract infection (UTI). S aureus accounts for 15% of bloodstream infections and may be associated with skin, soft tissues, or musculoskeletal infections. Salmonella species, N meningitides, and Streptococcus pyogenes account for most of the remaining infections.
 
As with most patients, the approach to the febrile child aged 3 months to 3 years consists of a targeted medical history, a complete physical examination, and the judicious use of the laboratory tests.

Medical History

The medical history should focus on factors that would predispose the infant or toddler to serious bacterial infection. 
 
History of present illness

Documentation of the child’s temperature and how it was measured is essential. A rectal temperature of more than 38.5^o C (101^o F) is abnormal in this age group. In addition to identifying when the fever started and how long it has lasted, a detailed search should be made for other symptoms, including but not limited to diarrhea, vomiting, rhinorrhea, cough, rash, and changes in weight or feeding habits.
 
Past medical history 

Every effort should be made to identify prior infectious episodes and risk factors for serious bacterial infections. Underlying chronic diseases, prior surgery, history of UTIs, and incomplete immunization to S pneumoniae or H influenzae type b must be specifically delineated. In children younger than 9 months, neonatal and perinatal history is also important.
 
Family medical history

Episodes of recurrent infections among siblings and first cousins or a history of maternal fetal loss raises suspicion of primary immunodeficiencies. Parental human immunodeficiency (HIV) status is essential information. A history of chronic infections (eg, hepatitis B, hepatitis C, tuberculosis) in the immediate or extended family is also important to obtain. The presence of acute illness in the family, such as croup or respiratory infection, is also important information.
 
Social history

Animal, insect, and sylvan exposure; exposure to contaminated potable water and sewage; recent travel (particularly international travel); and attendance at daycare provide epidemiologic and environmental clues to the etiology of fever. Exposure to sick individuals outside of the household is also critical information.
 
Review of systems

A detailed review of systems helps to identify other symptoms associated with fever. Important associations include rash, conjunctivitis, ear pain or drainage, lymphadenopathy, respiratory symptoms, changes in appetite, weight loss, diarrhea, vomiting, changes in frequency of voiding, pain with voiding, failure to bear weight, pain on passive motion of an extremity, and overt neurological symptoms.

Physical Examination

A careful and thorough physical examination is essential in the evaluation of the febrile child. Vital signs, including length and weight with percentiles, should be part of the evaluation. The child’s general state of nutrition, level of activity, and level of arousal should be noted. Close examination of the skin, lymphatics, eyes, ears, nose, and throat is necessary because many febrile infants have viral infections with associated rashes or associated respiratory symptoms. Inspection and auscultation of the chest should be included in all evaluations. The abdomen should be inspected for signs of distention. Auscultation may reveal signs of ileus or hyperactivity. The extremities should be evaluated for capillary refill; range of motion, signs of infection, and local tenderness should be evaluated. Neurological and developmental examinations appropriate for age should be performed.

Laboratory Evaluation, Assessment, and Management

The laboratory evaluation consists of two parts. The first part is dictated by epidemiological and focal findings uncovered by the history and physical examination. Children with severe cough and respiratory distress should undergo chest radiography as part of their evaluation; children with limp or evidence of focal infection should undergo appropriate imaging studies.
 
The second part of the evaluation is designed to identify patients at low risk for serious bacterial infections. Children who appear clinically ill, have a history of vomiting, have chest wall retractions with tachypnea, or have delayed capillary refill times are at increased risk for bacterial infection. Increasing fever also increases the risk of bacterial infection. Children aged 24-36 months with fever exceeding 39.5^o C and children aged 3-24 months with fever exceeding 39^o C have a higher risk of bacteremia than children with lower temperatures.⁷
 
Occult UTI is the most common cause of unexplained fever and bacteremia in this age group. Catheterized, unspun samples with more than 10 WBCs per high-power field or bacteria found in any of 10 oil immersion fields of a gram-stained sample is highly suggestive of infection. The presence of leukocyte esterase or nitrites by dipstick of unspun samples also suggests infection. Febrile children with suspicious urinalysis findings require cultures of both urine and blood. Urine cultures that yield more than 50,000 colony-forming units/mL are diagnostic of infection.⁸
 
WBC counts, absolute neutrophil counts, serum C-reactive protein concentration and serum procalcitonin concentration are additional metrics that help to distinguish further children at low risk for serious bacterial infection. Total WBC counts below 15,000 cells/μL, absolute neutrophil counts below 10,000/μL, C-reactive protein concentrations less than 40 mg/L, and serum procalcitonin levels less than 0.5 ng/mL identify children at low risk for serious bacterial infection.^1,9,10,11  
 
The risk factors for serious bacterial infections in febrile children aged 3-36 months are as follows:

• Physical examination findings: Ill appearance, fever, vomiting, tachypnea with retractions, and delayed capillary refill are associated with bacterial infection in more than 39.5% of febrile children aged 24-36 months and in more than 39% of children aged 3-24 months.
• Laboratory evaluation findings suggestive of serious bacterial infections
  • Urinalysis (unspun) - More than 10 WBC per high-power field, bacteria in any of 10 high power fields, or positive leukocyte esterase and nitrite findings
  • WBC count - More than 15,000/μL 
  • Absolute neutrophil count - More than 10,000/μL 
  • C-reactive protein level - More than 40 mg/L
  • Procalcitonin level - More than 0.5 ng/mL

For the most part, management should be individualized based on risk factors, clinical appearance, and clinical judgment. Ill-appearing children with poor capillary refill and children who have clinical signs and symptoms suggestive of meningitis need to managed in hospital and perhaps in the critical care setting. Children with focal infections such as sinusitis and pneumonia need to be managed with appropriate antimicrobial therapy.  
 
With the widespread use of pneumococcal vaccine in young children, the incidence of occult bacteremia in febrile children aged 3 months to 3 years has fallen from 4.6% to less than 1%.^12,2 As such, the evaluation has become more extensive to prevent overtreatment. In the absence of focal findings, any child in the target age group who appears ill or has excessive fever, vomiting, or tachypnea with retractions should be evaluated further. 

At a minimum, urinalysis, peripheral WBC count, and absolute neutrophil count should be obtained; if readily available, C-reactive protein or, preferably, serum procalcitonin concentration should also be obtained. Children with an abnormal WBC count, absolute neutrophil count, C-reactive protein level, or procalcitonin level should have a blood culture and should receive empiric antimicrobial therapy and close follow-up within 36 hours of the initial visit; children with an abnormal urinalysis findings should be managed in a similar fashion, with the addition of a urine culture.

Parents and medical professionals who want to supplement physical measures with medication in order to maximize the time that children spend without fever should use ibuprofen first and weigh the use of paracetamol plus ibuprofen over 24 hours.¹³

Antimicrobial Treatment

Empiric antimicrobial therapy must provide coverage against the suspected pathogens and must achieve high and sustained serum concentrations.¹⁴  In this setting, a single intramuscular dose of ceftriaxone has been shown to prevent sustained bacteremia in children whose initial blood culture has yielded S pneumoniae. In vitro, ceftriaxone is also effective against most strains of E coli, thus supporting the empiric use of this agent until bacterial culture results are known. Children at risk for S aureus infections should receive clindamycin as well. Limited data are available regarding the use of alternative agents.

Keywords

fever in the neonate, fever in the infant, fever in the toddler, serious bacterial infection, sepsis, meningitis, urinary tract infection, bacteremia, Haemophilus influenzae type b, Streptococcus pneumoniae, sexually transmitted infections, group B streptococcus, maternal fever, galactosemia, peripartum infection, fetal hypoxia, human immunodeficiency virus, HIV, hepatitis B, hepatitis C, syphilis, gonorrhea, chlamydia, leukocyte adhesion deficiency, urinary tract infection, UTI, failure to thrive, jaundice, cholestasis, herpes simplex virus, respiratory virus, bronchiolitis, pyelonephritis, Moraxella catarrhalis, Neisseria meningitidis, late-onset group B streptococcus, Staphylococcus aureus, Escherichia coli, Listeria monocytogenes, hospital-acquired organisms, methicillin-resistant Staphylococcus aureus, MRSA, otitis media, pneumonia, sinusitis, cellulitis, tuberculosis, croup