(Reuters) – The U.S. Centers for Disease Control and Prevention (CDC) said on Monday that COVID-19 can spread through the virus lingering in the air, sometimes for hours, acknowledging concerns widely voiced by public health experts on airborne transmission of the virus.
The CDC guidelines come weeks after the agency issued – and then deleted – a similar warning, sparking debate over how the virus is spread.
In Monday’s guidelines, the CDC said there was evidence that people with COVID-19 could infect others who were more than six feet away, in enclosed spaces with poor ventilation. .
Under such circumstances, the CDC said scientists believed the amount of droplets and smaller infectious particles, or aerosols, produced by people with COVID-19 became concentrated enough to spread the virus.
The CDC has long warned against transmission by small droplets that shoot through the air and typically fall to the ground, resulting in the six-foot social distancing rule. The aerosol droplets are still much smaller and can stay suspended in the air like smoke.
As the CDC points out that close contact transmission is more common than by air, a group of U.S. scientists warned in an unrelated open letter published Monday in the medical journal Science that persistent aerosols in the air could be a major source of COVID-19 transmission. (bit.ly/34pSPbH)
“The reality is that airborne transmission is the primary means by which transmission occurs at close range with prolonged contact,” the researchers said during a press call.
Viruses in aerosols can stay in the air for seconds to hours, travel more than two meters, and collect in poorly ventilated indoor air, leading to widespread events, the researchers said.
Since people with COVID-19 release thousands of virus-laden aerosols and far fewer droplets when breathing and speaking, scientists said the focus should be on protection from airborne transmission.
They also said public health officials should clearly differentiate between droplets ejected by coughing or sneezing and aerosols that can carry the virus greater distances.
Public health officials should stress the importance of moving activities outdoors and improving indoor air, as well as wearing a mask and social distancing, the letter said.