Infants were found to have higher SARS-CoV-2 nasopharyngeal viral loads at presentation but developed less severe disease compared with older children and adolescents, according to the results from a report published as a letter to the editor in Clinical Infectious Diseases.

Although published data suggest that COVID-19 is less severe in pediatric age groups, the relative contribution of infants and children to virus transmission is unknown. It is also unknown whether observations of high SARS-CoV-2 nasopharyngeal viral load in asymptomatic infants are generalizable to symptomatic infants, or how these compare to nasopharyngeal viral loads in older children. Furthermore, some data from adults suggest that viral load is positively correlated with COVID-19 severity, but how viral load correlates with severity across the pediatric age spectrum has not been established.

In this report, the investigators used reverse transcriptase polymerase chain reaction with the cobas SARS-CoV-2 assay (Roche Molecular Systems, Inc., Branchburg, New Jersey) to assess viral loads among infants, children, and adolescents who were hospitalized with symptoms suggestive of COVID-19 and subsequently discharged from a children’s hospital between March 14, 2002, and April 24, 2020.

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A total of 57 patients tested positive for COVID-19 infection, 35.1% of whom were infants aged ≤12 months. The older children ranged in ages from 1 to 21 years. Mean nasopharyngeal viral load was found to be significantly higher in infants compared with older children (mean cycle threshold values 21.05 vs 27.25; P <.01). However, the number of infants with severe disease was significantly lower compared with older patients (1 vs 12; P =.02). The mean time to test positivity from symptom onset was also lower in infants when compared with older patients (2 vs 3.8 days; P <.01), and similar proportions of both groups were tested within 7 days of symptom onset (91.2% vs 100%; P =.47).

According to the investigators, the results suggest that symptomatic infants have higher nasopharyngeal SARS-CoV-2 viral loads at presentation but develop less severe disease than older children and adolescents. Further investigation is needed to determine whether this is attributable to slightly earlier presentation to clinical care vs host biology. The investigators believe these data have implications for mitigating spread, especially in congregate settings like childcare facilities or hospital units that serve this population.


Zachariah P, Halabi KC, Johnson CL, Whitter S, Sepulveda J, Green DA. Symptomatic infants have higher nasopharyngeal SARS-CoV-2 viral loads but less severe disease than older children [published online May 20, 2020]. Clin Infect Dis. doi:10.1093/cid/ciaa608