A person with COVID-19 could be contagious for a longer period of time than if they had the flu, according to the CDC website. The Associated Press reported that the CDC noted sharp increases in several measures, including lab tests and emergency room visits.

Though symptoms of a cold and the flu are similar, key differences set them apart. The two illnesses develop at different rates, with colds often beginning slowly and the flu taking hold more quickly. Colds are typically a mild illness, while the flu can become severe and, in some cases, deadly.

The Milwaukee Health Department tracks COVID-19, flu and RSV levels through public wastewater testing. Officials provided a behind-the-scenes look.

Illinois health officials advised of an uptick in respiratory illnesses on Monday as families geared up for holiday celebrations in the following days.

Is COVID going around again? The CDC's wastewater surveillance system suggests the virus is growing in prevalence.

Respiratory viruses will likely increase over the holidays as many of us travel and expand our social networks. But we have several tools to help keep us from getting sick.