Not a virus. Using a mask to stop a virus is like using a chain link fence to stop mosquitoes.
Maybe like a cloth mask. But N-95 will stop most coronaviruses if properly fited. But those masks will also create more aerosols by exhalation by an infected person through the valve. Cloth masks might do that too, breaking larger droplets into smaller droplets.
In between there are surgical masks which will stop some droplets both inhaled and exhaled. Might be better than nothing, not enough data to really know.