But what constitutes as "high" or "substantial?" And what parts of the United States and more specifically, Central California, are seeing these high rates of COVID-19?
Along with the new guidelines, the CDC released a map showing which areas are experiencing surging COVID rates. For a county to be considered an area with "high" transmission rates, the total number of new cases per 100,000 people in the past seven days must be greater than 100.
In counties considered to have "substantial" COVID-19 transmission, the total number of new cases per 100,000 people in the last seven days must be between 50 and 99.99, the CDC map shows.
In the Central Valley, Merced, Madera, Fresno and Kings counties are all currently listed by the CDC as having "high" transmission rates. Meanwhile, Tulare and Mariposa counties are "substantial."
Southern California and Bay Area counties also show high transmission rates, according to the map.
CDC COVID-19 Transmission Map by County
Click on a county below for more information, or search for a county in the table.Graphics not displaying correctly? Click here to open the map in a new window or click here to open the table 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.