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Updated: Sep 5, 2025

Infection of Primary Nasal Epithelial Cells Grown at an Air-Liquid Interface to Characterize Human Coronavirus-Host Interactions
Published on: September 22, 2023
Mild and Asymptomatic Coronavirus Disease in Children, Adolescents, and Household Contacts and Prolonged Viral
Márcia Borges Machado1, Thamirys Cosmo Grillo Fajardo1, Lourival Benedito de Oliveira1
1Faculty of Medicine of Jundiaí (FMJ), R. Francisco Teles, 250-Vila Arens II, Jundiaí-SP 13202-550, Brazil.
Method:
This was a prospective, observational, and descriptive cohort study. Nasopharyngeal swabs and blood were collected six times at weekly intervals. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) tests and immunoglobulin (Ig) G and IgA assays were used to test for COVID-19.
Results:
Overall, 419 children and 253 adults were enrolled. There was a significant correlation between qRT-PCR confirmation and the 1 to <5 years age group (p=0.038). Serology changes or recent infections were detected significantly in children <6 months (IgG, p=0.006; IgA, p=0.001) and >5 years of age (IgA, p=0.040; IgG, p=0.031). The mean and median time-to-positivity (using qRT-PCR) was 17 days, with a minimum of 6 and a maximum of 34. Among adults, the mean and median time-to-positivity was 12.6 and 9 days, respectively, with a minimum of 6 and a maximum of 45.
Conclusion:
Oligosymptomatic conditions may delay diagnosis and facilitate viral transmission. Pediatric-focused research is required, and specific protective measures for children <6 months of age should be considered.
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