After observing that some COVID-19 patients who had recovered and had been discharged were readmitted with positive polymerase chain reaction (PCR) tests, Chinese investigators retested 60 COVID-19 patients who had been discharged to in-home quarantine after hospitalisation. PCR testing status of these patients at hospital discharge was unknown.
Among the retested patients (median age, 47), none had symptoms of COVID-19, but 10 tested positive for SARS-CoV-2 between 4 and 24 days after discharge (6 had positive anal swab results, and 5 had positive nasopharyngeal swab results; 1 patient had positive results for both). One patient had donated plasma 9 days before testing positive. Outcomes for patients who received the plasma were not reported.
This study suggests that patients who previously were positive for SARS-CoV-2 by PCR and who were discharged after hospitalisation frequently have persistently positive PCR tests, yet the clinical significance and infectivity are minimal. These PCR tests likely are responding to noninfective RNA fragments and do not represent detection of viable virus. The fact that these patients reportedly were under strict home isolation argues more for persistence of RNA detection than for reinfection.