Norovirus is an unpleasant – and extremely contagious – stomach bug known for sickening hundreds of people at a time on cruises, in schools and in nursing homes.

You might wonder how you can protect yourself and your family members from norovirus.

Here’s one surprising fact: hand sanitizer won’t protect you.

Norovirus is an extremely crafty bug and each particle comes with its own protective shield of sorts to help it survive as long as possible.

“Alcohol can’t break the shield. A detergent like soap can most of the time,” said Dr. Michelle Barron, senior medical director of infection prevention and control at UCHealth University of Colorado Hospital on the Anschutz Medical Campus.

“Be really diligent with hand washing. Make sure you’re washing your hands really well with soap and water and that you’re cleaning surfaces with bleach. Also, be very conscious about food preparation,” said Barron who is one of Colorado’s top infectious disease experts and is also a professor at the University of Colorado School of Medicine.

Barron said hand sanitizers, which contain alcohol, can be useful to protect people from other illnesses like COVID-19, colds and the flu. So, be sure to keep hand sanitizer on hand.

But, if you, your children or your co-workers are dealing with stomach illnesses, you should stay home so you don’t spread the virus and wash your hands very frequently with good old soap and warm water.

Barron also recommends cleaning surfaces as often as possible with bleach-based detergents, which can kill norovirus.

While Barron protects herself well from infectious diseases, she has gotten norovirus herself. Once, when she was traveling, she grabbed a sandwich at the airport to eat on the plane. A little while later, she started feeling lousy. At first, like many people suffering from stomach viruses, she thought she had food poisoning.

But, once she returned home and was stuck in the bathroom for about 24 hours, she realized that she was suffering from norovirus instead.

“It’s a very infectious virus that causes pretty severe diarrhea and vomiting for 24 to 36 hours. If anybody in your household gets it, it’s just so infectious that everyone around you is likely to get it,” Barron said.

Symptoms from food poisoning, in contrast, usually last just a couple of hours. And food poisoning typically stems from bacteria that have developed in food, like mayonnaise dishes that need to remain cold and have sat out in the sun too long.

Unfortunately, people who are infected with norovirus sometimes don’t know they have it until they get sick. In the meantime, they can touch food or surfaces in schools like desks and notebooks. The virus stays alive on the surface, then when other people touch the same spot, the infection spreads.

“It only takes one or two particles of this virus to make you sick,” Barron said.

According to the CDC, each person with norovirus can shed billions of particles of the disease.

Norovirus is the most common culprit for stomach bugs, but just like flu viruses, there are many types of norovirus. And, unlike the flu, there’s no vaccine.

So, once you get norovirus, all you can do is let the virus run its course and try to protect people around you from getting sick.

“In terms of what to do to treat it, the No. 1 thing is to stay home. There’s no treatment. You have to let it run its course,” Barron said.

Barron said norovirus is common when people are gathering in close quarters and are eating together.

She encourages hosts to be sure to use utensils to serve food so people don’t accidentally spread illnesses with their hands.

Food on cruise ships can serve as a source of infection.

“Cruises have these huge buffets. Everyone goes and samples the food. Hands and foods can be infected. And, once you ingest the virus, you’re going to get sick,” Barron said.