Detection of respiratory viruses in febrile infants suggests lower risk of bacterial infection

1. Respiratory viruses were identified in 55% of febrile infants; those older than 28 days had a lower risk of bacterial infection when they tested positive for a respiratory virus.

2. Human rhinovirus (HRV) detection in well-appearing febrile infants did not affect risk of concurrent urinary tract infection or risk of concurrent bacterial infection in infants younger than 28 days old.

Evidence Rating Level: 2 (Good)

Study Rundown: The evaluation of a febrile infant is a clinical challenge that often involves cultures and empiric antibiotic treatment due to the vulnerability of infants in their first few months of life. There is an increasing role for the clinical detection of a variety of respiratory viruses, including the common HRV, with polymerase chain reaction (PCR). In this study, researchers examined records of febrile infants who presented to the emergency room or were admitted from an outpatient setting. Authors analyzed the results of testing for respiratory viruses with the presence of a bacterial infection in infants. The results show that viruses were detected in more than half (55%) of febrile infants tested. Infants without respiratory viruses detected were more than 3 times more likely to have a bacterial infection than those in whom a non-HRV respiratory virus was detected. Infants in whom HRV was identified also had a reduced risk of bacterial infection to a lesser degree (about 2 fold), excluding urinary tract infections. Together, these results support previous studies showing decreased risk of bacterial infections in infants with documented viral infection. These findings suggest that respiratory virus, and specifically HRV, detection in infants older than 28 days has predictive value that can influence the clinical evaluation and management of a febrile infant. The limitations of this study include difficulty distinguishing virus colonization from invasive infection, and lack of information about specific symptomalogy.

Relevant Reading: Timing of First Respiratory Virus Detections in Infants: A Community-Based Birth Cohort Study

In-Depth [retrospective cohort]: Participants included 10 964 well-appearing febrile infants who presented to the emergency room or were admitted directly after outpatient evaluation. 37% of these infants had PCR testing for respiratory viruses (RVPCR). Of those tested, 55% (2212/4037) of infants were positive for a respiratory virus, with HRV the most commonly detected (35% of infants with virus detected). A variety of other viruses were detected at low rates. Infants from 28-90 days old were more likely to have a respiratory virus identified than infants younger than 29 days (61% vs. 39% P <0.001). Bacterial infections — including meningitis, bloodstream infection, and UTIs — were identified more frequently in younger infants compared to older ones (11.5 vs, 8.8% P=0.01). Infants without any respiratory virus detected were 3.66 times more likely to have a bacterial infection identified than those with a non-HRV virus detected (95% CI: 2.53-5.31). Infants in whom no respiratory virus was identified were 2.1 times more likely to have a bacterial infection than those with HRV (95% CI: 1.43-3.15).

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