When is coronavirus most contagious?

The virus causing COVID-19 disease is likely most contagious before symptoms begin to show, which is typically around five days after infection, per multiple studies.

One study, for example, published in the journal Nature Medicine found that “patients with the respiratory disease COVID-19 may begin to shed, or excrete, infectious SARS-CoV-2 coronavirus 2–3 days before the first symptoms appear,” the researchers previously explained in a statement emailed to Fox News.

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A study out of Singapore reached the same conclusion: "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," researchers wrote.

According to the Centers for Disease Control and Prevention (CDC), “Available data indicate that persons with mild to moderate COVID-19 remain infectious no longer than 10 days after symptom onset.” However those suffering more severe cases may be infectious for up to 20 days following symptom onset, the agency noted.

The CDC says the incubation period for COVID-19, or time from exposure to onset of symptoms, is up to 14 days.

"The incubation period for COVID-19 is thought to extend to 14 days, with a median time of 4-5 days from exposure to symptoms onset," the agency wrote. "One study reported that 97.5% of persons with COVID-19 who develop symptoms will do so within 11.5 days of SARS-CoV-2 infection."

After patients recover, there may be traces of detectable virus lingering in upper respiratory specimens for months, though infectiousness is deemed unlikely.

Fox News' James Rogers and Chris Ciaccia contributed to this report. 

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