Population-level screening for SARS-CoV-2

Highlights

• More than 34,000 280,000 participants provided > 700,000161,000 nasal swabs for COVID-19 testing
• Presence of symptoms at time of test correlated to higher viral load in positive subjects
• No difference in positivity between male and female participants
• No difference in viral load of participants from different age groups
• Children at private schools were less likely to test positive than adults at same schools

Summary

The COVID-19 pandemic continues to prevent a return to normalcy. Rapid and widespread asymptomatic testing is key to containing the spread of the SARS-CoV-2 virus, allowing for early detection and isolation of cases. In this study, we screened more than 280,00034,000 healthcare workers, first responders, students, faculty, and staff across San Diego County, USA for COVID-19. The presence of symptoms was significantly correlated with higher viral load, but most of the positive participants were asymptomatic at the time of testing. The positivity rate among preschool-grade 12 schools that remained open for in-person teaching was similar to the positivity rate at the University of California San Diego, with the children in private schools being less likely to test positive than the adults at the same schools. This suggests that the safety measures and repeated testing actions taken by participating healthcare and educational facilities were effective in preventing outbreaks, even before vaccines were available, and that a similar combination of risk-mitigation strategies and repeated testing may be successfully adopted by other healthcare and educational systems.

Key words: SARS-CoV-2; COVID-19; viral load; symptoms; testing; population