County Health Department and ProMedica talk about norovirus, RSV, flu, COVID-19. Also find historical data on illnesses.

When broken down by state, most of the country is experiencing elevated respiratory illness, including a few states with “very high” ratings that act as national hotspots, CDC data shows.

Viral sicknesses have risen in early 2025 amid the ongoing “quad-demic” in the U.S., referring to three respiratory viruses and one gastrointestinal disease, according to the Centers for Disease Control and Prevention (CDC) data.

After the holiday season and an uptick in travel, California faces a rise in respiratory illnesses, prompting health experts to talk of a “quad-demic.” The term refers to the simultaneous spread of four major viruses: COVID-19,