coronavirus September 1, 2021 11:26 pm Stanford Study Finds Surgical Masks Most Effective in Limiting COVID-19 Spread A recent Stanford University study reveals that wearing a surgical mask is very effective in limiting the spread of COVID-19. Ian Cull reports. US & World Videos 2:19 San Francisco barbershop struggles to stay open after pandemic 0:51 Alameda County using dogs to detect COVID 3:57 Interview: Doctor's perspective on COVID 4 years after shutdown started 2:27 Marking 4 years since COVID-19 shut down the Bay Area 2:09 CDC updates COVID isolation guidelines