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.

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

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.

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.

CHICOPEE, Mass. (WWLP) – A new strain of Norovirus is impacting children and adults, and it’s spreading in our state. Respiratory illnesses continue to surge, that’s because it’s colder and more people are indoors allowing germs to spread, but it can be prevented.

The Health Department confirmed three people at the shelter tested positive for the virus among a cluster of 28 people suffering from acute gastrointestinal illness.

As a new strain of norovirus is racking up a high amount of cases nationwide, we take a look at it and ways to avoid being infected by it.