The Centers for Disease Control and Prevention (CDC) on Wednesday expanded its definition of “close contact” of someone with coronavirus, now saying that multiple brief encounters can also lead to transmission of the virus. 

The previous definition of close contact, which is used for determining who should quarantine, was being within 6 feet of an infected person for at least 15 minutes. 

The new standard now defines close contact as being within 6 feet of an infected person for at least 15 minutes over a 24-hour period, making clear that multiple separate encounters that add up to more than 15 minutes also count. ADVERTISEMENT

The change comes after the CDC and Vermont health officials published a report finding that a prison employee in Vermont contracted the virus after “multiple brief encounters” with inmates who later tested positive. The 22 encounters added up to 17 minutes over an eight-hour shift, the report said.

Some of the inmates were not wearing masks, the CDC said, reinforcing the importance of mask wearing. 

“This article adds to the scientific knowledge of the risk to contacts of those with COVID-19 and highlights again the importance of wearing face masks to prevent transmission,” a CDC spokesperson said. 

The new definition will increase the number of people who are classified as being a “close contact” during contact tracing investigations. It also shows the importance of wearing a mask even during brief encounters. 

“Wearing a mask is one of the most effective steps you can take to help stop the spread of COVID-19,” the CDC spokesperson said. 

In another update to how the virus spreads, the CDC said earlier this month that coronavirus can spread through “airborne transmission” to people who are more than 6 feet away under certain conditions, particularly indoors in areas with poor ventilation.

The Hill