May 22, 2020

expert reaction to study on PCR testing results from 60 people after clinical recovery from COVID-19

A study, published in JAMA Network Open, reports PCR testing results from 60 people after clinical recovery from COVID-19.

Prof Babak Javid, Principal Investigator, Tsinghua University School of Medicine, Beijing, and Consultant in Infectious Diseases at Cambridge University Hospitals, said:

“This study looked at a cohort of 60 patients discharged from hospital in China after recovering from COVID-19.  They found 10/60 patients were still swab positive for considerable periods of time after discharge.  The authors suggest that this is viable viral shedding, since they recommend PPE for people in contact with discharged patients. But actually, they never attempted to culture viable virus from any of these patients.  Data from other studies, most recently from the S. Korea CDC suggests that these positive swab results late into the disease process do NOT represent viable virus and do not pose an infection risk.  This is also corroborated by this study: one of the patients had considerable contact with health care workers after discharge (for the purpose of donating convalescent plasma for treating other COVID-19 patients).  All these health care workers were quarantined and tested for COVID-19, and none tested positive.  In summary, it seems that patients well into recovery are quite unlikely to be contagious despite having coronavirus RNA isolated from samples.  Nonetheless, careful cohort studies in larger patient numbers looking at viable virus recovery (which this study doesn’t) would be welcome.”

Dr Louise Berry, Consultant in Infectious diseases and virology, Nottingham University Hospitals, said:

“The paper tells us that the patients recovering from COVID-19 are still testing positive on PCR testing several weeks following infection. This is being observed in many other centres, but we have to be clear here that PCR positivity does not equate to ongoing infectivity. A PCR tells us that there is still viral genetic material (RNA) in various specimen samples but this does not tells us about the presence of live virus nor infective potential of these patients. Other studies to date, including those looking at whether the virus is still viable using virus culture and epidemiological studies which look at transmission events do not currently indicate infectiousness beyond the first two weeks of infection.”

“Coronavirus Disease 2019 Test Results After Clinical Recovery and Hospital Discharge Among Patients in China” by Jinru Wu et al. was published in JAMA Open Network at 16:00 UK time Friday 22 May.

All our previous output on this subject can be seen at this weblink: www.sciencemediacentre.org/tag/covid-19

Declared interests

Prof Babak Javid: No conflicts

None others received.