Korean researchers have found that Covid-19 can spread from mild and moderate patients for fewer than 12 days after symptoms appear.

To find out the coronavirus transmissibility duration, a joint research team, led by Professors Kim Min-chul, Chung Jin-won, Choi Seong-ho from Chung-Ang University and Professor Park Man-seong from Korea University, took a closer look by cultivating the virus from mild and secondary patients at Chung-Ang University Hospital. 

The researchers found that although it took 34 days for confirmed patients to test negative since they showed symptoms, it took seven days for the virus to be removed in the cultivating test aimed to verify infectious virus. 

They also discovered that the Covid-19 virus could be cultivated for a maximum of 12 days after symptoms appeared. Based on this, the team concluded that the Covid-19 virus’s propagation duration is seven days in median value and 12 days at a maximum.

“The study showed that 50 percent of Covid-19 patients showed positive in the PCR test even one month after symptom appeared. In terms of virus cultivation test, however, the transmittable virus was gone within seven days,” Professor Park said.

Professor Chung also said, “For mild and moderate Covid-19 patients, the infectious virus was detected up to 12 days. We expect to apply the study results to provide scientific evidence on deciding the appropriate self-quarantine period for Covid-19 patients and evaluate the risk of secondary transmission by close contacts. 

The study results were published in the New England Journal of Medicine.