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Coronavirus transmission occurs during pre-symptomatic period

the staff of the Ridgewood blog

Ridgewood NJ, A Brief Communication article published in Nature presents analysis on temporal trends in viral shedding in COVID-19 patients. The study included data from 94 laboratory-confirmed COVID-19 patients in Guangzhou, China—including 414 total throat swabs taken as long as 32 days after symptom onset—to analyze trends in SARS-CoV-2 viral load.The study also included information on 77 identified transmission events, from both inside and outside China, to analyze SARS-CoV-2 transmission dynamics. The researchers observed high viral load in COVID-19 patients immediately after symptoms presented, which tapered off over a period of approximately 21 days. The researchers concluded that the viral load could potentially peak around the time symptoms present, or possibly slightly earlier. Based on the viral load data and case data from the 77 transmission events, the researchers estimated that 44% of the transmissions occurred during the index case’s pre-symptomatic period and that COVID-19 patients become infectious 2.3 days before symptom onset, with a peak in infectiousness around 0.7 days before symptom onset. The study does not evaluate transmissibility of individuals with asymptomatic infection, and the viral load data may not directly correlate to an individual’s degree of infectiousness. Additionally, the article notes that clinical treatment could affect viral load in COVID-19 patients.

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