CDC COVID risk map highlights areas of high transmission in Bay Area

SAN FRANCISCO -- The CDC released new guidelines that people wear masks indoors, regardless of vaccination status, in regions facing "high" or "substantial" COVID-19 transmission.

But what constitutes as "high" or "substantial?" And what parts of the United States and more specifically, the Bay Area, are seeing these high rates of COVID-19?

RELATED: Indoor mask mandate to take effect at midnight in 7 Bay Area counties

Along with the new guidelines, the CDC released a map showing which areas are experiencing surging COVID rates. In Bay Area, Alameda, Contra Costa, Napa, Marin, San Francisco Solano and Sonoma counties are all currently listed by the CDC as having "high" transmission rates, while Santa Clara and San Mateo counties are "substantial."

CDC COVID-19 Transmission Map by County

Click on a county below for more information, or search for a county in the table.

Map not displaying correctly? Click here to open in a new window.

Cases are rising across the United States as concerns around the delta variant grow. According to an internal document from the CDC, this variant appears to cause more severe illness and spreads as easily as chickenpox, with each infected person, on average, infecting eight or nine others. The original lineage was about as transmissible as the common cold, with each infected person passing the virus to about two other people on average.

VACCINE TRACKER: How California is doing, when you can get a coronavirus vaccine

Having trouble loading the tracker above? Click here to open it in a new window.

RELATED STORIES & VIDEOS:

• Everything to know about California's reopening
• Where you still have to wear a mask in CA
• What we know about the delta variant of COVID-19 following new CDC report
• Cheat sheet: What you can and can't do after being fully vaccinated
• Can a workplace require the coronavirus vaccine? Here's what we found
• COVID-19 vaccine: Everything to know about your 2nd Pfizer or Moderna shot
• CA COVID-19 Vaccine Tracker: See your status here
• These CA counties are way ahead in vaccinations
• Map shows everywhere you can get a COVID-19 test in the Bay Area
• Data tracker: Coronavirus cases, deaths, hospitalizations in every Bay Area county
• Get the latest updates on California EDD, stimulus checks, unemployment benefits
• Coronavirus origin: Where did COVID-19 come from?
• What is a COVID-19 genetic, antigen and antibody test?
• What does COVID-19 do to your body and why does it spread so easily?
• Coronavirus Timeline: Tracking major moments of COVID-19 pandemic in San Francisco Bay Area