key: cord-0816330-07pyr5v1
authors: Jang, Sukbin; Rhee, Ji-Young; Wi, Yu Mi; Jung, Bo Kyeung
title: Viral Kinetics of SARS-CoV-2 over the preclinical, clinical, and postclinical period
date: 2020-11-05
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2020.10.099
sha: 39b7a8f0d8e9b45c294fc560866e449c5bb4d29e
doc_id: 816330
cord_uid: 07pyr5v1

BACKGROUND: It is necessary to know the viral kinetics and conduct epidemiologic investigations of confirmers to prevent the spread of the new infectious disease COVID-19 to the community. To date, no study has been published on viral kinetics during the preclinical and clinical periods of SARS-CoV-2. METHODS: A confirmed case was defined as a patient with positive results by real-time reverse transcription polymerase chain reaction (RT-PCR) assay for SARS-CoV-2. Both specimen types were collected over the whole clinical course in all patients. Asymptomatic patients who had been screened for COVID-19 due to a strong epidemiologic link were also enrolled. The study population included 54 hospitalized patients with confirmed COVID-19. RESULTS: COVID-19 shows a very high viral load on the day of symptom development which then decreases overall. Rapid viral proliferation was observed 0–5 days before symptoms developed. Cycle threshold (Ct) value was lowest in clinical course from 5 days before symptoms to 10 days after symptoms occurred(Ct < 30). The rRT-PCR results were negative approximately 3 weeks after the onset of symptoms. However, there was a continuous pattern that was negative and positive for up to 6 weeks and more. CONCLUSION: Considering the characteristic that COVID-19 has a high viral load before symptoms appear, it is necessary to consider to expand the scope of epidemiological investigations. Since there is very low possibility of transmission after 10 days of symptom occurrence, it may be considered to release isolation after 10 days of symptom occurrence in limited resource situations. This study allows for the planning of epidemiological investigations, patient's ward supply, and follow-up of patients through sequential changes in viral loads over the entire clinical course. In addition, it is possible to estimate the clinical time at which the patient is present.

Coronavirus disease 2019 (COVID-19), which started in Wuhan in December 2019, has spread worldwide. As of 20 May 2020, the newly emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (genus Betacoronavirus, family Coronaviridae) has been reported in 227 countries with more than 4,789,205 confirmed cases and 318,789 deaths. 1 Contact screening and extensive testing are proposed methods of blocking the transmission of infectious diseases during pandemics.

It is necessary to know the viral kinetics and conduct epidemiologic investigations of confirmers to prevent the spread of COVID-19. To date, there have been no published data on viral loads before and after the onset of symptoms. The purpose of this study was to infer viral kinetics, including preclinical, clinical, and post-clinical periods, to assist in epidemiological investigations, prevent transmission, and predict the patient's progress.

A confirmed case was defined as a patient with positive results by real-time reverse transcription polymerase chain reaction (RT-PCR) assay for SARS-CoV-2 in upper respiratory specimens (nasopharyngeal and oropharyngeal swabs), with or without a lower respiratory specimen (sputum).

Both specimen types were collected over the whole clinical course in all patients. Patients who had no symptoms, but had been screened for COVID-19 due to a strong epidemiologic link, such as family members, were also included upon laboratory-confirmation.

Real-time reverse transcriptase polymerase chain reaction (rRT-PCR) was used to detect SARS-CoV-2.

RNA was extracted from clinical samples with the QIAamp Viral RNA Mini kit (QIAGEN, Hilden, Germany), QIAsymphony RNA Kit (QIAGEN, Hilden, Germany), and ExiPrep 16 Dx (Bioneer, Korea); manufacturer' s instructions were followed. All specimens were handled in accordance with the laboratory biosafety guidelines of the Korea CDC for SARS-CoV-2.

The optimal concentration of primers and probes was synthesized using published sequences 

The Institutional Review Board (IRB) at Dankook University Hospital reviewed and approved the study protocol (IRB registration No. 2020-03-029-001); the requirement for written consent was waived.

The study population included 54 hospitalized patients with confirmed COVID-19 ( We evaluated viral kinetics by serial rRT-PCR of respiratory specimens from 54 patients (figure 1). All patients were sampled regularly by nasopharyngeal swabs, lower respiratory specimens, and within the J o u r n a l P r e -p r o o f sputum (figure 1). RT-PCR results from 6 days before symptoms to 48 days after symptoms were confirmed.

We classified the patient's test results from the date of symptom occurrence and calculated the average Ct value (figure 2). The Ct value at the day of symptom development was the lowest at 13.47(11.85~16.13). Ct value was lowest in clinical course from 5 days before symptoms to 10 days after symptoms occurred (Ct < 30).

Out of the twelve people who tested SARS-CoV-2 before symptoms appeared, six were family members of confirmatory patients and other six were in close contact from an instructor who was identified as COVID-19 in the dance fitness class. The other was a Korean immigrant from the United States and was confirmed by laboratory screening for visits. In one case, a test conducted six days before the symptom occurred showed negative findings (Ct value was 35.82).

In patients36 who received systemic corticosteroid, Ct value decreased 10 days after methylprednisolone administration. In the rRT-PCR test performed with the lower respiratory tract specimen, the Ct value decreased from 32.09 to 20.8 ( figure 3) .

COVID-19 shows a very high viral load on the day of symptom development which then decreases overall. Rapid viral proliferation was observed from 0-6 days before the onset of symptoms, suggesting that the risk of transmission is extremely high due to a significant amount of viral load in the early stages of symptoms and preclinical period. A recent study found that a Ct value of 30 or less showed positive findings in viral culture, although viral culture positive Ct does not mean infectious dose. 2, 3 In our finding, the Ct value is as low as 30 or less from 5 days before symptom onset to 10 days after symptom onset.

The epidemiological investigation currently being conducted by the WHO(World Health Organization) guideline is set as of the 2nd day before patient symptoms are confirmed. 4 However, our results show it is possible to see a rapid increase in the virus 5 days before symptom occurrence and a very high viral load that can occur 5 days before to 10 days after symptoms occur. Within this Ct range, the virus The presentation is clear and concise.

Reviewer #1:

2. There are several grammar and spelling errors in the article.

Reviewer #1: 2. There are several grammar and spelling errors in the article. This study is limited by a small sample size (n=54). In addition, a more comprehensive graph can be created if the results of rRT-PCR from the contact before the onset of symptoms can be added. Further research is needed to determine how much viral load is infectious.

In conclusion, changes in viral load allow us to estimate when patients will develop symptoms and determine the scope of epidemiological investigations. This study of viral kinetics provides a basis for estimating the inpatient discharge time and the patient's isolation release time, which can makes the supply and demand of the hospital room predictable. All other authors have no potential conflicts to disclose.

Conceptualization: Rhee JY.

Methodology: Rhee JY. year-old man with a history of diabetes, was hospitalized on the 5th day of cough and fever. On the 10th day of symptom onset, dyspnea worsened and tachypnea persisted even after high flow nasal cannula oxygen therapy. On the 10th day of symptom development, methylprednisolone was administered at 0.5mg / kg for 3 days and then stopped. Oxygen demand was reduced, but it was worsened on the 4th day after discontinuation, so methylprednisolone was taken at 1mg / kg for 3days. (The concomitant drugs used during the period of use of methylprednisolone were nafamostat, piperacillin/tazobactam, levofloxacin, and lansoprazole.) After clinical improvement, the prednisolone dose was reduced and finally stopped after 10 days. In the rRT-PCR test after discontinuation of corticosteroid administration, the Ct value was continuously decreased and negative was confirmed on the 19th day after the final discontinuation.

J o u r n a l P r e -p r o o f 

Jung BK Writing -review and editing: Rhee JY Approval of final manuscript: all authors

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