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.

Fact checked by Nick Blackmer Flu cases are beginning to rise after a slow start to the season, with respiratory illnesses increasing nationwide in the week ending Dec. 14, according to the Centers for Disease Control and Prevention (CDC).

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.