(CNN) – The Centers for Disease Control and Prevention is tweaking its guidance about how coronavirus spreads.
It reiterates that prolonged, close contact is the worst culprit, especially if people aren’t wearing masks and are closer than 6 feet apart.
The change to the guidance involves whether the virus can linger in the air after an infected person leaves an area.
The CDC says some reports indicate transmission like that can happen in enclosed, poorly ventilated spaces, but is rare.
The agency says activities that require heavy breathing like exercising or singing can increase the likelihood of this type of spread.