In one-quarter of young children with several common respiratory viruses, detection persisted for at least four weeks.

Almost a decade ago, the high prevalence of respiratory viral infections among young children was demonstrated in a longitudinal study (NEJM JW Infect Dis Oct 2015 and Clin Infect Dis Oct 2015; 61: 1217-1224); nonetheless, quantifying the duration of viral shedding has been challenging. Now, in the PREVAIL cohort study spanning 15 months in Cincinnati and involving healthy mother-infant pairs, investigators have identified factors influencing the shedding of common respiratory viruses.

Infant nasal swabs collected weekly by mothers were tested with PCR for influenza A and B, RSV, human metapneumovirus, parainfluenza 1, 2 and 3, rhino/enterovirus, bocavirus and endemic human coronaviruses. Weekly surveys of symptoms as well as medical records yielded detection of 1489 viral infections in 9801 nasal swabs from 101 adherent pairs. Key findings include:

• 39% of detected viral infections occurred in symptomatic infants 
• in general, prolonged viral shedding (four weeks or longer) was detected in 23% of participants
• median duration of viral detection for most viruses was one week, but was longer (median, two weeks) for bocavirus, rhino/enterovirus and one of the human coronaviruses
• longest duration of detection (more than five weeks) was seen for rhino/enterovirus, bocavirus, adenovirus and parainfluenza type 1
• prolonged shedding was not seen for influenza and was minimal (11%) for RSV
• prolonged detection occurred more often in children with their first viral-specific infection or with viral co-infection
• no correlation between age, sex or symptoms (fever or cough) and duration of viral shedding was noted.

Comment: Although it is interesting that a quarter of respiratory viral infections in this longitudinal cohort caused shedding for least four weeks, the investigators did not pair positive PCR results with viral cultures; thus, infectivity cannot be inferred. Additionally, because the rhinoviruses were not individually typed, some infections categorised as persistent may have been new infections. Perhaps most intriguing is the significant number of positive PCR results not associated with symptoms. This study confirms that asymptomatic viral shedding is common, sometimes prolonged, and possibly infectious. But – much as we struggled to determine for SARS-CoV-2 – for how long?

Deborah Lehman, MD, Clinical Professor of Pediatrics and Assistant Dean of Student Affairs, David Geffen School of Medicine, University of California, Los Angeles, USA.

Teoh Z, et al. Factors associated with prolonged respiratory virus detection from PCR of nasal specimens collected longitudinally in healthy children in a U.S. birth cohort. J Pediatr Infect Dis Soc 2024; 13: 189-195.

This summary is taken from the following Journal Watch title: Infectious Diseases.