The CDC does recommend face covering to prevent spread of Covid-19 coronavirus. Any face covering contains secretions from the nose and mouth from normal speaking, laughing, coughing and sneezing, which aerosolizes the virus and disperses it into the air.
Asymptomatic carriers may transmit the virus, so feeling healthy does not mean you do not need to wear a mask. Antibody positive people can carry and transmit it too. Please wear your mask in any public space!