Quoted: “A mask that is not covering the nose will not stop a person infected with SARS-CoV-2 from contaminating the air in front of them when they exhale. Similarly, a mask covering only the mouth will fail to prevent an uninfected person from inhaling contaminated air. Since it does not take a lot of virus particles to cause infection, a partially worn mask may not be effective enough. This reminds me of when I see people wearing a bicycle helmet without buckling the strap or wearing it so loosely that it doesn’t cover the front of their head. The intention might be there, but there is a higher risk of head injury following an accident if the helmet is unable to do what it is designed to do.”
— Ajay Sethi, PhD, MHS, associate professor, Department of Population Health Sciences at the University of Wisconsin-Madison.