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Countries across the world, including the U.S., are in various phases of reopening, but concerns of a so-called “second wave” of the coronavirus pandemic have cropped up. A new study out of Singapore, however, suggests that COVID-19 patients are not infectious 11 days after getting sick.
“In a local study from a multicenter cohort of 73 COVID-19 patients, when the Ct value was 30 or higher (i.e. when viral load is low), no viable virus (based on being able to culture the virus) has been found,” the researchers wrote in the study. “In addition, virus could not be isolated or cultured after day 11 of illness.”
The researchers noted that a separate study out of Germany found “the degree of viral shedding was very high in the first week of symptoms,” supporting their findings.
A man with a facemask walks past a wall mural in Singapore’s Little India district on Saturday, May 16, 2020. (AP Photo/YK Chan)
“In sputum, sgRNA (also known as (viral subgenomic messenger RNAs, which are only present in actively-infected cells) declined over days 10 – 11, and in throat swabs, sgRNA was not detected after day 5,” the researchers added. “Infectious virus was cultured from throat and lung specimens in the first week of symptoms, but none after day 8 in spite of high viral loads detected by regular PCR.”
“Based on the accumulated data since the start of the COVID-19 pandemic, the infectious period of SARS-CoV-2 in symptomatic individuals may begin around 2 days before the onset of symptoms, and persists for about 7 – 10 days after the onset of symptoms,” the researchers concluded. “Active viral replication drops quickly after the first week, and viable virus was not found after the second week of illness despite the persistence of PCR detection of RNA.”
Singapore has had a lower number of COVID-19 patients compared to other countries around the world. According to data compiled by Johns Hopkins University, 32,433 patients have tested as positive, but it has an exceptionally low fatality rate, at 23 deaths.
By comparison, the U.S., the most affected country on the planet, has had more than 1.66 million patients test positive for COVID-19 and is approaching 100,000 deaths.
As of Monday morning, more than 5.51 million coronavirus cases and 346,700 have been diagnosed worldwide as a result of the coronavirus pandemic.