Masks help to filter out aerosol that is generated in our respiratory tract when we breathe or speak. ( They) are most effective at filtering out larger aerosol particles and less effective at filtering out the smallest ones, this is conceptually similar to driving a car when there are a lot of insects about -- the large ones tend to impact against the windshield whereas the small ones follow the air flow around the car.

Bryan Bzdek

The viral load in fecal matter and the fraction of resulting aerosol containing the virus is unknown. Even if the virus were contained in the produced aerosols, it is unknown whether the virus would still be infectious ; there is not yet clear evidence for fecal-oral transmission, the study authors suggest that whenever possible we should keep the toilet seat down when we flush, clean the toilet seat and any other contact areas frequently, and wash our hands after using the toilet. While this study is unable to demonstrate that these measures will reduce transmission of the SARS-CoV-2 virus, many other viruses are transmitted though the fecal-oral route, so these are good hygiene practices to have anyway.