Abstract
OBJECTIVESThe objective of the study was to conduct a follow-up investigation of 10 asymptomatic patients at diagnosis among the 98 confirmed coronavirus disease 2019 (COVID-19) cases reported in Busan between February 21, 2020 and March 13, 2020 to determine whether asymptomatic infection and transmission during asymptomatic period are possible.METHODSThe study analyzed 10 asymptomatic, confirmed COVID-19 cases to determine whether asymptomatic infection is possible. We conducted in-depth interviews with patients and guardians; interviews with primary physicians; review of medical records and drug utilization review (DUR) reports; and base station-based location tracking.RESULTSAmong the 98, confirmed COVID-19 cases reported in Busan, the study analyzed 10 (10.2%) asymptomatic patients at diagnosis. The results confirmed that two (2.0%) patients reported to be asymptomatic during the initial epidemiological investigation, but turned symptomatic before diagnosis as per the in-depth interview results. Four cases (4.0%) of early detection led to confirmed diagnosis during the incubation period and presentation of symptoms after diagnosis. In addition, the remaining four patients (4.0%), having no subjective symptoms nor specific findings on chest radiography and computed tomography, remained asymptomatic until the isolation order was lifted. With regard to whether transmission during the asymptomatic period is possible, it was found that one out of 23 household contacts of the confirmed patients was identified as an additional confirmed case after coming in close contact with an index patient during the presymptomatic period.CONCLUSIONSAmong the 98 confirmed cases, asymptomatic infection was confirmed in four cases (4.0%). In addition, there was one additional confirmed case in which the patient was a family member who came in close contact with an index patient during the incubation period, thereby confirming that transmission during the asymptomatic period is possible. The possibility of transmission during the asymptomatic period has been confirmed; therefore, it is necessary to review the measures for expanding contact tracing that is currently being applied starting one day prior to the onset of symptoms.
Highlights
Since the first confirmed case of coronavirus disease 2019 (COVID-19) in Busan on February 21, 2020, a total of 98 confirmed cases have been reported over a 22-day period, up to March 13, 2020
Ten asymptomatic, confirmed COVID-19 cases reported in Busan between February 21, 2020 and March 13, 2020 were investigated to find if asymptomatic infection transmission is possible
Follow-up investigation was conducted on the status and date of symptom onset until complete recovery, based on the comparison of statements given by patients and family members, opinions of primary physicians on patient condition, and test results such as real-time reverse transcription polymerase chain reaction (PCR), chest radiography, and computed tomography (CT) scan results
Summary
Since the first confirmed case of coronavirus disease 2019 (COVID-19) in Busan on February 21, 2020, a total of 98 confirmed cases have been reported over a 22-day period, up to March 13, 2020. On February 21, 2020, a Chinese research team published an article titled “Presumed asymptomatic carrier transmission of COVID-19” [2] in the Journal of the American Medical Association (JAMA), which recognized asymptomatic infection and transmission. In light of this information, the Korea Centers for Disease Control and Prevention (KCDC) changed its position from completely dismissing the possibility of asymptomatic transmission to recognizing the possibility of asymptomatic infection and transmission, and advocating the need to strengthen preemptive and aggressive disease control measures [3]
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