The Centers for Disease Control and Prevention have urged the public to wear face masks indoors again as the tripledemic — it includes COVID-19, the flu, and RSV – continues to become a growing concern this winter.

The CDC released a Dec. 8 report which found that 13.7% of Americans now live in areas rated as "high" COVID-19 Community Levels, up from 4.9% last week.

Additionally, 38.1% of citizens are deemed to be in "medium" areas and 48.2% in "low" areas.

Many of the high-risk communities are located in highly populated metropolitan areas including Los Angeles and New York. A health advisory warning personnel of rising respiratory illness in New York was sent out to hospitals and health clinics. New York counties listed in the "high" tier include Kings, Queens, New York, Suffolk, Bronx, and Nassau County.

Los Angeles officials have strongly recommended that people wear masks indoors. Los Angeles, Santa Clara, and San Bernardino counties in the state are listed as "high" tier.

The Arizona counties of Maricopa and Pima counties are also listed as "high."

"When you put on your mask for these few weeks during this surge, it is about the people of LA County. it is about every individual, every visitor, our healthcare workers, essential workers and other people who serve. In addition to vaccination, it is one of the easiest things everyone can do right now," Barbara Ferrer, Los Angeles County director of public health, said in a press release on Friday.

CDC officials say they are attempting to develop metrics that will assist regional leaders in identifying and containing respiratory illnesses.

"We have also been working on trying to develop, as rapidly as possible, metrics that would be useful at state or regional levels for being able to visualize the level of overall respiratory viral activity," Barbara Mahon, a CDC employee, said at an advisor meeting last week.

CDC NYC