7/31/2023 0 Comments Virus detected csv2qif![]() ![]() Our study was driven by the hypothesis that COVID-19 patients in the early stage of their illness would shed infectious SARS-CoV-2 in respiratory secretions and contaminate surfaces that can contribute to transmission of the virus. It appears likely that patients early in the course of COVID-19 could more readily transmit and contaminate surfaces in the clinical and community setting, leading to an increased risk of virus transmission 21. Additional studies investigating shedding of infectious virus from COVID-19 patients consistently report that it is highest early in the course of infection 17, 18, 19, 20. However, extensive surface contamination with SARS-CoV-2 by a symptomatic patient has been demonstrated in a hospital setting 16 where a link was established between the presence of environmental contamination and the quantity of SARS-CoV-2 RNA, using cycle threshold (C t), detected in the clinical sample, and day post-symptom onset and shedding of infectious SARS-CoV-2. Recent reports suggest that there is little evidence to support transmission of SARS-CoV-2 through contaminated surfaces 13, 14 and the United States Centers for Disease Control and Prevention recently suggested that surfaces are not a significant mode of transmission of SARS-CoV-2 15. Transmission is further clouded by uncertainty over the minimal infectious dose in humans although classical human volunteer studies with the 229E coronavirus have shown clinically evident attack rates as high as 50% with extremely low inoculation doses of 0.6–1.5 TCID 50 11, 12. There has been debate about the degree to which respiratory secretions of varying particle sizes, including those produced by exhaled breath, may be responsible for transmission of the virus 5, 7, 8, 9, 10 in part due to confusion over the relationships between a PCR signal and how that result relates to the underlying quantities of viral non-genomic RNA, virus genomes, and infectious virions. ![]() fomites), and small particle aerosols, with close contact being a major risk associated with transmission 5, 6. The modes for SARS-CoV-2 transmission are considered to occur through multiple routes including large respiratory droplets, contact (direct and indirect i.e. In response, public health measures were implemented based on the best available data related to the presumed modes of transmission and based on recommendations for other respiratory viruses 2, 3, 4. ![]() Since February 2020, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has gripped the globe 1. Together, our findings offer compelling evidence that large respiratory droplet and contact (direct and indirect i.e., fomites) are important modes of SARS-CoV-2 transmission. SARS-CoV-2 isolated from patient respiratory tract samples caused illness in a hamster model with a minimum infectious dose of ≤ 14 PFU. Infectious virus in clinical and associated environmental samples correlated with time since symptom onset with no detection after 7–8 days in immunocompetent hosts and with N-gene based C t values ≤ 25 significantly predictive of yielding plaques in culture. Infectious SARS-CoV-2 with quantitative burdens varying from 5 plaque-forming units/mL (PFU/mL) up to 1.0 × 10 6 PFU/mL was detected in 151/459 (33%) of the specimens assayed and up to 1.3 × 10 6 PFU/mL on fomites with confirmation by plaque morphology, PCR, immunohistochemistry, and/or sequencing. To explore the potential modes of Severe Acute Respiratory Coronavirus-2 (SARS-CoV-2) transmission, we collected 535 diverse clinical and environmental samples from 75 infected hospitalized and community patients. ![]()
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