Asymptomatic Covid-19 patients emit a similar amount of virus to those with symptoms, stressing the need to strengthen tracing and managing infected people to prevent silent spreads, a recent study has shown.
A research team of the Department of Infectious Diseases at Soonchunhyang University Hospital (SCHUH) published the results of a retrospective cohort study on Covid-19 patients isolated at a community center in Daegu, in the Journal of the American Medical Association (JAMA) on Aug. 6.
The research team divided 303 Covid-19 patients isolated at the community treatment center into two groups -- 214 symptomatic and 89 asymptomatic patients -- and performed reverse transcription-polymerase chain reaction (RT-PCR) to compare virus emission. The median age was 25, and only 12 of them had associated diseases.
Of the 303 people, 193 showed symptoms from the time of quarantine, and 21 out of 110 asymptomatic patients developed symptoms after entering the facility. The average period for the onset of symptoms was 15 days, ranging from 13 to 20 days.
On the other hand, 89 patients have not developed symptoms from entering the facility and were discharged after full recovery.
On the eighth, ninth, 15th, and 16th day of isolation, RT-PCR was performed for nasopharyngeal, oropharyngeal, and sputum samples, and the Cycle threshold (Ct) value for measuring virus emission was also confirmed.
The test result revealed that the Ct values of the asymptomatic and symptomatic patients were similar, showing no difference in virus emission depending on the presence of symptoms. The result implied that the virus could silently spread from asymptomatic patients.
"In our study, a considerable number of patients did not develop symptoms until their full recovery," said Professor Kim Tark of the Department of Infectious Diseases of SCHUH, the first author of the paper. "The nation’s countermeasures to actively seek out and isolate infected patients seem appropriate."
The title of the study is "Clinical Course and Molecular Viral Shedding Among Asymptomatic and Symptomatic Patients With SARS-CoV-2 Infection in a Community Treatment Center in the Republic of Korea."
SCHUH in Bucheon, Gyeonggi Province, sent three of its professors -- Kim Ho-jung of Department of Emergency Medicine, Lee Hui-jeong of Family Medicine, and Lee Cheol-gu of Surgery Department -- to the temporary community treatment center in Daegu, where mild Covid-19 patients received treatment under isolation.