The actress shared a string of photos of her sister’s hospital room, with a huge yellow tube pumping air in and a member of the medical staff dressed in full PPE.
She wrote: “My sister Kelly, who already has lupus, now has COVID-19. This is her hospital room. One of you Non-Mask wearers did this.
“She does not have an immune system. The only place she went was the pharmacy.
“There is no testing in her county unless you are symptomatic, & then it’s 5 day wait for results.
“Can YOU FACE THIS ROOM ALONE? Wear a mask! For yourself and others. Please.”
Stone is the latest in a number of stars who are using social media to ask people to wear masks.
Last week, Charmed actress Alyssa Milano shared a video of her hair loss as a result of Covid-19 as she begged people to take the illness seriously and wear masks.