WORCESTER, Mass. – There's concern about a new "silent" wave of COVID-19. Doctors say it could lead to more illness around the holidays because people might not know the risk or have mild symptoms and not get tested. 

The CDC says more than 20 states have "high" or "very high" activity of the virus, which causes COVID-19 in wastewater. 

Massachusetts and New Hampshire are listed in the "very high" category. Worcester's medical director said it's important to take a test if you don't feel well, and take precautions to not spread the virus. 

"If you get a flu-like illness these days, you can't assume. It is worthy of a test," Dr. Michael Hirsh said. "There is a test for both flu and COVID, and if you have either of those things test positive, it's not a big fancy prescription for anything. You should just stay home essentially until you don't have any of those symptoms."

Hirsh said people who are older, or who are at risk and become ill, should contact their doctor about the best course of treatment.  

He also recommended getting the latest version of the COVID vaccine.