The U.S. is seeing a "quad-demic" as cases of COVID-19, flu, RSV and norovirus spread at the same time. Experts said this is what you need to know.

Norovirus, also known as the stomach bug, is spreading across the U.S. Here's what to know about the contagious virus and how best to prevent an infection.

Rates of norovirus in that CDC system have reached levels at or above last season's peak in all regions of the country. Norovirus test positivity rates look to be the worst in the Midwest, in a grouping of states spanning Kansas through Michigan.

The cases mark the fourth norovirus outbreak on Holland America ships since early December, following others on its Eurodam, Rotterdam and Zuiderdam vessels. Other companies, including Cunard Line and Princess Cruises also saw outbreaks in recent weeks.

You can also get norovirus by touching objects or surfaces that are contaminated and then putting your hands in your mouth without washing them first. Hand-washing with soap and water is key, as hand sanitizer will not do the trick in the case of norovirus, experts say.

As many people know all too well, norovirus is a wicked illness. It causes gastroenteritis, a fancy name for violent

The brief but miserable symptoms have no treatment except hydration and rest. Doctors have several tips on how to stop the spread.

No. Hand sanitizer is simply not as effective against norovirus as it at killing other pathogens due to the virus's firm shell, Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, told TODAY.com recently.

Health care providers are not required by law to report norovirus cases to the state health department, so the data reflect estimates from schools, long-term care facilities and day cares.

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

“We are seeing somewhere in between 10 to 20 patients each day in the Children’s Hospital who need admissions,” Chief Medical Officer for Kentucky Children’s Hospital Dr. Lindsay Ragsdale said. It’s one of many reasons why Kentucky is one of four states ranked high for respiratory illness activity by the CDC.