Background At the beginning of the pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), little was known about its actual rate of infectivity and any COVID-19 patient positive in laboratory testing was supposed to be highly infective and a public health risk factor. Methods One hundred oropharyngeal samples were obtained during routine work flow of testing symptomatic persons by quantitative polymerase chain reaction (qPCR) and were inoculated onto cell culture of VeroB4 cells to study the degree of infectivity of SARS-CoV-2 in vitro. Quantification by virus titration and an external standard using synthetic RNA gave the breaking point of infectivity in SARS-CoV-2 in vitro. Results A clear negative correlation (r = − 0.76; p < 0.05) could be asserted between the viral load in quantitative polymerase chain reaction (qPCR) and the probability of a successful isolation in serial isolation experiments of specific oropharyngeal samples positive in qPCR. Quantification by virus titration and an external standard using synthetic RNA indicate a Cq between 27 and 30 in E-gene screening PCR as a breaking point in vitro, where infectivity decreases significantly and isolations become less probable. Conclusions This study showed that only the 21% of samples with the highest viral load were infectious enough to transmit the virus in vitro and determined that the dispersion rate in vitro is surprisingly close to those calculated in large retrospective epidemiological studies for SARS-CoV-2. This raises the question of whether this simple in vitro model is suitable to give first insights in dispersion characters of novel or neglected viral pathogens. The statement that SARS-CoV-2 needs at least 40,000 copies to reliably induce infection in vitro is an indication of its transmissibility in Public Health decisions. Applying quantitative PCR systems in diagnosis of SARS-CoV2 can distinguish between patients providing a high risk of transmission and those, where the risk of transmission is probably limited to close and long-lasting contacts.
【저자키워드】 SARS-CoV-2, Infectivity, Transmission pattern in vitro, Quantitation of viral infectivity, 【초록키워드】 public health, coronavirus, SARS-CoV2, pandemic, Infection, Diagnosis, Transmission, in vitro, risk factor, severe acute respiratory syndrome Coronavirus, virus, Laboratory testing, RNA, Probability, polymerase chain reaction, Viral, PCR, Transmissibility, Viral load, qPCR, symptomatic, Cell culture, Patient, Isolation, Pathogens, Oropharyngeal, experiment, infectious, novel, respiratory, Quantitative, quantitative PCR, retrospective, E-gene, COVID-19 patient, high risk, Chain Reaction, Virus titration, acute respiratory syndrome, acute respiratory syndrome coronavirus, acute respiratory syndrome coronavirus 2, indication, negative correlation, Epidemiological study, positive, viral pathogens, quantitative polymerase chain reaction, in vitro model, infective, Public, risk of transmission, Cell, decrease, polymerase chain, raise, Result, highest, caused, significantly, inoculated, calculated, less, question, long-lasting, induce, Applying, 【제목키워드】 virus isolation, oropharyngeal swab, Isolation, correlation, quantitative PCR, Cq value, in vitro model,