High Amounts of SARS-CoV-2 Precede Sickness Among Asymptomatic Health Care Workers

Abstract

Whether SARS-CoV-2 positivity among symptomatic subjects reflects past or future disease may be difficult to ascertain. We tested a cohort of 9449 employees at work at the Karolinska University Hospital, Stockholm, Sweden for SARS-CoV-2 RNA and antibodies, linked the testing results to sick leave records and determined associations with past or future sick leave using multinomial logistic regression. ClinicalTrials.gov NCT04411576. Subjects with high amounts of SARS-CoV-2 virus, as indicated by the Cycle threshold (Ct) value in the PCR, had the highest risk for sick leave in the two weeks after testing (OR 11.97 (CI 95% 6.29-22.80)) whereas subjects with low amounts of virus had the highest risk for sick leave in the past three weeks before testing (OR 6.31 (4.38-9.08)). Only 2.5% of employees were SARS-CoV-2 positive while 10.5% were positive by serology and 1.2% were positive in both tests. Serology-positive subjects were not at excess risk for future sick leave (OR 1.06 (95% CI, 0.71-1.57)). High amounts of SARS-CoV-2 virus, as determined using PCR Ct values, associates with development of sickness in the next few weeks. The results support the concept that PCR Ct may be informative when testing for SARS-CoV-2 is performed.