Asymptomatic Children May Transmit COVID-19 in Communities

Heidi Splete

September 04, 2020

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About 22% of children with COVID-19 infections were asymptomatic, and 66% of the symptomatic children had unrecognized symptoms at the time of diagnosis, based on data from a case series of 91 confirmed cases.

Although recent reports suggest that COVID-19 infections in children are generally mild, data on the full spectrum of illness and duration of viral RNA in children are limited, wrote Mi Seon Han, MD, PhD, of Seoul (South Korea) Metropolitan Government–Seoul National University Boramae Medical Center, and colleagues.

To examine the full clinical course and duration of COVID-19 RNA detectability in children with confirmed infections, the researchers reviewed data from 91 individuals with confirmed infections. The children ranged in age from 27 days to 18 years, and 58% were male. The children were monitored at 20 hospitals and 2 isolation facilities for a mean 21.9 days. The findings were published in JAMA Pediatrics.

Overall, COVID-19 viral RNA was present in the study population for a mean 17.6 days, with testing done at a median interval of 3 days. A total of 20 children (22%) were asymptomatic throughout the study period. In these children, viral RNA was detected for a mean 14 days.

"The major hurdle implicated in this study in diagnosing and treating children with COVID-19 is that a considerable number of children are asymptomatic, and even if symptoms are present, they are unrecognized and overlooked before COVID-19 is diagnosed," the researchers noted.

Of the 71 symptomatic children, 47 (66%) had unrecognized symptoms prior to diagnosis, 18 (25%) developed symptoms after diagnosis, and 6 (9%) were diagnosed at the time of symptom onset. The symptomatic children were symptomatic for a median of 11 days; 43 (61%) remained symptomatic at 7 days' follow-up after the study period, 27 (38%) were symptomatic at 14 days, and 7 (10%) were symptomatic at 21 days.

A total of 41 children had upper respiratory infections (58%) and 22 children (24%) had lower respiratory tract infections. No difference in the duration of virus RNA was detected between children with upper respiratory tract infections and lower respiratory tract infections (average, 18.7 days vs. 19.9 days).

Among the symptomatic children, 46 (65%) had mild cases and 20 (28%) had moderate cases.

For treatment, 14 children (15%) received lopinavir-ritonavir and/or hydroxychloroquine. Two patients had severe illness and received oxygen via nasal prong, without the need for mechanical ventilation. All the children in the case series recovered from their infections with no fatalities.

The study's main limitation was the inability to analyze the transmission potential of the children because of the quarantine and isolation policies in Korea, the researchers noted. In addition, the researchers did not perform follow-up testing at consistent intervals, so the duration of COVID-19 RNA detection may be inexact.

However, the results suggest "that suspecting and diagnosing COVID-19 in children based on their symptoms without epidemiologic information and virus testing is very challenging," the researchers emphasized.

"Most of the children with COVID-19 have silent disease, but SARS-CoV-2 RNA can still be detected in the respiratory tract for a prolonged period," they wrote. More research is needed to explore the potential for disease transmission by children in the community, and increased surveillance with laboratory screening can help identify children with unrecognized infections.

The study is the first known to focus on the frequency of asymptomatic infection in children and the duration of symptoms in both asymptomatic and symptomatic children, Roberta L. DeBiasi, MD, and Meghan Delaney, DO, both affiliated with Children's National Hospital and Research Institute, Washington, and George Washington University, Washington, wrote in an accompanying editorial. The structure of the Korean public health system "allowed for the sequential observation, testing (median testing interval of every 3 days), and comparison of 91 asymptomatic, presymptomatic, and symptomatic children with mild to moderate upper and lower respiratory tract infection, identified primarily by contact tracing from laboratory-proven cases."

Two take-home points from the study are that not all infected children are symptomatic, and the duration of symptoms those who are varies widely, they noted. "Interestingly, this study aligns with adult data in which up to 40% of adults may remain asymptomatic in the face of infection."

However, "The third and most important take-home point from this study relates to the duration of viral shedding in infected pediatric patients," Dr. DeBiasi and Dr. Delaney said (JAMA Pediatr. 2020 Aug 28. doi: 10.1001/jamapediatrics.2020.3996).

"Fully half of symptomatic children with both upper and lower tract disease were still shedding virus at 21 days. These are striking data, particularly since 86 of 88 diagnosed children (98%) either had no symptoms or mild or moderate disease," they explained. The results highlight the need for improvements in qualitative molecular testing and formal studies to identify differences in results from different testing scenarios, such as hospital entry, preprocedure screening, and symptomatic testing. In addition, "these findings are highly relevant to the development of public health strategies to mitigate and contain spread within communities, particularly as affected communities begin their recovery phases."

Dr. Michael E. Pichichero

The study is important because "schools are opening, and we don't know what is going to happen," Michael E. Pichichero, MD, of Rochester General Hospital, N.Y., said in an interview.

"Clinicians, parents, students, school administrators and politicians are worried," he said. "This study adds to others recently published, bringing into focus the challenges to several suppositions that existed when the COVID-19 pandemic began and over the summer."

"This study of 91 Korean children tells us that taking a child's temperature as a screening tool to decide if they may enter school will not be a highly successful strategy," he said. "Many children are without fever and asymptomatic when infected and contagious. The notion that children shed less virus or shed it for shorter lengths of time we keep learning from this type of research is not true. In another recent study the authors found that children shed as much of the SARS-CoV-2 virus as an adult in the ICU on a ventilator."

Dr. Pichichero said he was not surprised by the study findings. "A similar paper was published last week in the Journal of Pediatrics from Massachusetts General Hospital, so the findings in the JAMA paper are similar to what has been reported in the United States."

"Availability of testing will continue to be a challenge in some communities," said Dr. Pichichero. "Here in the Rochester, New York, area we will use a screening questionnaire based on the CDC [Centers for Disease Control and Prevention] symptom criteria of SARS-CoV-2 infections to decide whom to test."

As for additional research, "We have so much more to learn about SARS-CoV-2 in children," he emphasized. "The focus has been on adults because the morbidity and mortality has been greatest in adults, especially the elderly and those with compromised health."

"The National Institutes of Health has issued a call for more research in children to characterize the spectrum of SARS-CoV-2 illness, including the multisystem inflammatory syndrome in children [MIS-C] and try to identify biomarkers and/or biosignatures for a prognostic algorithm to predict the longitudinal risk of disease severity after a child is exposed to and may be infected with SARS-CoV-2," said Dr. Pichichero. "NIH has asked researchers to answer the following questions."

  • Why do children have milder illness?

  • Are there differences in childhood biology (e.g., gender, puberty, etc.) that contribute to illness severity?

  • Are there genetic host differences associated with different disease severity phenotypes, including MIS-C?

  • Are there innate mucosal, humoral, cellular and other adaptive immune profiles that are associated with reduced or increased risk of progressive disease, including previous coronavirus infections?

  • Will SARS-CoV-2 reinfection cause worse disease as seen with antibody-dependent enhancement (ADE) in other viral infections (e.g., dengue)? Will future vaccines carry a risk of the ADE phenomenon?

  • Does substance use (e.g., nicotine, marijuana) exacerbate or trigger MIS-C through immune activation?

"We have no knowledge yet about SARS-CoV-2 vaccination of children, especially young children," Dr. Pichichero emphasized. "There are different types of vaccines – messenger RNA, adenovirus vector and purified spike proteins of the virus – among others, but questions remain: Will the vaccines work in children? What about side effects? Will the antibodies and cellular immunity protect partially or completely?"

The researchers and editorialists had no financial conflicts to disclose. Dr. Pichichero had no financial conflicts to disclose.

SOURCE: Han MS et al. JAMA Pediatr. 2020 Aug 28. doi:10.1001/jamapediatrics.2020.3988.

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