Characteristics of persistence and infectivity of SARS-CoV-2 Omicron in children

In a recent study posted on medRxiv* Preprint server, researchers have characterized the persistence and infectivity of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Omicron among children.

Background

Since the first report of coronavirus disease (COVID-19) in 2019, the understanding of SARS-CoV-2 infection has evolved with the emergence of new variants. In July 2020, the US Centers for Disease Control and Prevention (CDC) recommended a 10-day quarantine period for individuals infected with SARS-CoV-2 without the need for relevant negative results. did.

In September 2021, the Florida Department of Health (FDOH) determined that a SARS-CoV-2 test was negative and that an infected child could return to school earlier than 10 days if there were no symptoms. did.

In January 2022, the CDC updated its guidelines, shortening the quarantine period to five days and allowing infected adults / children to return to work / school if they are enthusiastic. Nevertheless, masking was mandatory for another 5 days. In addition, in February 2022, FDOH allowed the return of infected children after five days of quarantine, without undergoing testing or using masks.

About research

In this study, researchers characterized the prevalence and infectivity of SARS-CoV-2 omicrons among children. Patients positive for SARS-CoV-2 have polymerase chain reaction (PCR) or rapid results antigen The test (RAT) was identified by the University of Florida (UF) Pediatrics Clinic or referred by a nurse at a local public school.

They enrolled children who showed symptoms for more than 5 days in sampling from 20 December 2021 to 21 February 2022. Parental samples were also collected when multiple children of the same family were enrolled in the study. After enrollment, samples of nasal swabs were obtained from 31 children (under 16 years) and 8 from 3 parents.

The team collected two specimens from each participant. One sample was immediately tested with Binax NOWRAT and the other sample was frozen to subsequent reverse transcriptase quantitative PCR (RT-qPCR), culture test, and measurement. Viral loadAnd genomic sequencing.

Patients who had a positive test result during the initial follow-up returned on day 7, 10 or until a negative result was recorded. Various cell lines were used for virus culture, including LLC-MK2, Vero E6, A549 and HEK293T cells. They observed the cells for a month and confirmed the presence of the virus by RT-PCR testing when the cytopathic effect (CPE) was revealed.

Survey results

Two-thirds of the children were boys, with a median age of seven. Ten had a negative RAT result at enrollment on the 4th day (or later) of onset of symptoms or after the first positive result (from UF Health or school referral). They observed at least one positive RAT in the remaining children. After that, 14 people were negative.

Assuming that all children were SARS-CoV-2 positive before the final positive result, the authors found that on day 5, more than one-third of them were SARS-CoV-2 positive and 48% were SARS-CoV-2 positive. Calculated to be still positive. RAT up to the 7th day. The team then estimated the duration of the child who was positive over time by fitting a parametric survival model.

The model predicted that the child would remain positive for an average of 7.74 days, with a 10% reduction in the probability of becoming positive by day 12. SARS-CoV-2 cultures were performed on 23 samples. Virus cultures were positive in 16 samples, all positive for RAT. Seven culture-negative samples were also RAT-negative. In addition, there was a significant correlation between RAT and culture results.

Forty samples were RAT positive and all were positive on the RT-qPCR test. Of the 25 RAT-negative samples, 9 were RT-qPCR positive. Four of these samples were cultured with negative results. Sequencing revealed that all positive samples were Omicron BA.1 variants.The Phylogenetic analysis No significant variability was found, consistent with the circulation of a single SARS-CoV-2 clade.

Conclusion

The authors reported that nearly half of infected children were SARS-CoV-2 positive for at least two days when they returned to school under the CDC’s January 2022 guidelines. Masks would have reduced transmission, but given FDOH’s February 2022 recommendations, mask practice was controversial in Florida.

From a public health perspective, it is essential to limit SARS-CoV-2 transmission by school-infected children. Therefore, extending the quarantine period of 5 days before returning to school should be considered in light of the need for negative RAT results.

*Important Notices

medRxiv publishes unpeer-reviewed preliminary scientific reports and should not be considered definitive, guide clinical / health-related behaviors, or be treated as established information.