Some transmission of SARS-CoV-2 occurs after seven, 10 days

There is some onward transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from household contacts released from quarantine after seven or 10 days, according to research published in the Jan. 1 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Melissa A. Rolfes, Ph.D., from the CDC COVID-19 Response Team, and colleagues analyzed interim data from an ongoing study of household transmission of SARS-CoV-2 to examine the proportion of household contacts who had detectable virus after a shortened quarantine period. For 14 days, household contacts of index patients completed a daily symptom diary and self-collected respiratory specimens, which were tested for SARS-CoV-2.

The researchers found that 59 percent of the 185 household contacts had detectable SARS-CoV-2 at any time; 76 and 86 percent of test results were positive within seven and 10 days, respectively, after the index patient's illness onset date. The chance of remaining asymptomatic and receiving negative test results through day 14 was 81 and 93 percent, respectively, among household contacts who received negative SARS-CoV-2 test results and were asymptomatic through day 7 or through day 10.

"Although persons might be more adherent to a shorter quarantine period, such a policy is not without risk for further spread," the authors write. "Timely access to a sufficiently sensitive test at the end of a shorter quarantine period will help identify household contacts with SARS-CoV-2 infection."