Where norovirus outbreaks commonly occur and tips to help you avoid and prevent infection

From the common cold to strep throat, there are a lot of viruses and bacteria that can spread from person to person. Norovirus isn’t any different – it’s a group of viruses that can be very easily spread and is often the cause of outbreaks of illness, especially in large group settings.

Although there are times of the year when norovirus outbreaks are more common, it’s not considered “seasonal” like the common cold or influenza. It can occur at any time and in any setting, especially if precautions aren’t taken to help prevent it.

Here, we’ll explain when a norovirus infection is considered an outbreak, and why and how outbreaks occur. We’ll also go over where norovirus outbreaks commonly occur, ways to prevent norovirus and how to protect yourself from infection during and after an outbreak.

When are norovirus infections considered an outbreak?

Norovirus infections are considered an outbreak when two or more people experience similar symptoms from a common exposure. The Centers for Disease Control and Prevention (CDC) says that there are an average of 2,500 norovirus outbreaks reported in the U.S. each year.

While you can become infected with norovirus anywhere or at any time of the year, outbreaks more commonly occur in countries north of the equator between November and April, and between April and September in countries that are in the southern hemisphere.

Norovirus symptoms usually occur just 12-48 hours after you become infected, but it is possible to experience symptoms as soon as 10 hours after infection. Common symptoms include diarrhea, nausea, stomach cramping and vomiting.

There is no vaccine to prevent a norovirus infection, and the only way to get rid of an infection is to let your immune system clear it naturally.

Why and how norovirus can cause outbreaks

Norovirus is a group of viruses that can cause gastroenteritis, which is an inflammation of the stomach and intestines, leading to uncomfortable symptoms. While most viruses and bacterial infections are contagious, the way norovirus spreads makes it one of the most contagious and common causes of illness outbreaks in the U.S.

Outbreaks of norovirus usually occur in settings where there are a lot of people in close, crowded settings, sharing breathing space, bathrooms, serving utensils, bedding and other contaminated surfaces and objects. In the U.S., health care facilities like hospitals or long-term care facilities have a higher risk of norovirus outbreaks, but they can also occur at daycares, schools, restaurants, catered events and cruise ships.

Norovirus is the leading cause of temporary vomiting and diarrhea in the U.S., and it’s also the leading cause of food-borne illnesses. Anyone can get norovirus, but some people, including children under five and adults over 85, can experience more serious symptoms.

Norovirus can spread easily by:

• Close contact with a person who has the virus through things like shaking hands, talking or kissing
• Touching contaminated surfaces and objects, then touching your mouth or nose, as norovirus can survive for weeks outside of the body
• Eating or drinking contaminated foods or beverages

Because norovirus spreads most easily where there are a lot of people in close contact and settings where food is prepared, there are specific places to take extra precautions. And because some foods can naturally carry norovirus, it’s important to keep an eye on what and where you eat.

Norovirus can spread easily in hospitals and long-term health care facilities

Hospitals and long-term health care facilities are at higher risk of norovirus outbreaks because they have several risk factors that are unique to their environments. This is why hospitals and other health care facilities have strict hygiene protocols in place to reduce risk of an illness outbreak. Some of the risk factors can include:

• Contact with contaminated stool – This is the main reason that norovirus spreads so easily, as norovirus can be found in poop for several weeks after recovery. Improper handwashing and infected airborne particles are typically the main causes of the spread of norovirus via contaminated poop.
• Shared rooms – Typically, long-term care facilities have dense living spaces and shared rooms, making it easier for the virus to pass from person to person.
• Use of proton pump inhibitors (PPIs) – PPIs don’t cause norovirus, but they can increase the risk of contracting it. PPIs are used to treat conditions like chronic acid reflux (GERD), esophagitis and other GI issues by reducing the amount of stomach acid the body produces. While they can help with certain conditions, they can disrupt the good bacteria in the gut, leaving you more susceptible to a norovirus infection.
• Compromised immune systems – Patients in these facilities typically have weaker immune systems than other people, which can make it more difficult for them to clear the virus quickly and completely. This can cause them to experience more severe symptoms and complications from symptoms, like dehydration, which can be fatal, especially in older populations.
• Decreased hygiene – Arthritis, dementia and other conditions that affect older people can make mobility and dexterity difficult, which in turn can lead to poor hygiene and increased risk of contracting illnesses.

Daycare facilities and schools can be affected by norovirus outbreaks

While outbreaks at daycare facilities and schools are less common than in care facilities, they can happen for a few reasons:

• Close contact – Children and young adults in these settings are frequently in prolonged, close contact with one another in small rooms, enabling the virus to transmit via particles in the air.
• Infected surfaces – Since the virus can live for days on surfaces and objects, transmission of norovirus can happen easily. Young children in particular are more likely to touch contaminated surfaces and objects, then put their hands in their mouths.
• Improper handwashing – Daycare facilities usually have children who aren’t potty trained, which can require daycare providers to handle contaminated soiled diapers and help infected children wipe after they use the bathroom.

Norovirus outbreaks have been linked to restaurants and large-scale events

People are usually in close contact with one another in these settings, making for easy transmission. However, improper food preparation and even some foods can also contribute to an outbreak. This is why proper handwashing is part of a restaurant staff’s standard operating procedure. Risk factors include:

• Infected food service workers – The people who handle food are frequent transmitters of norovirus. Contamination can occur from touching ready-to-eat foods, like fruits, vegetables, salads and sandwiches. But it can also happen with foods that are served raw, or touched and contaminated after they’ve been cooked.
• Contaminated shellfish – Oysters, clams, mussels and scallops can naturally carry norovirus, so they’re frequently linked to outbreaks, especially if they’re raw or undercooked. Oysters in particular are a big cause because they’re almost always eaten raw or barely cooked.
• Foods contaminated at the source – These can include oysters harvested from contaminated water, or fruits and vegetables watered with contaminated water while being grown.

Norovirus outbreaks can happen on cruise ships

While outbreaks on cruise ships are usually widely reported, they don’t happen as commonly as you may think. But they can still occur due to:

• Contaminated food and drinks – Infected food service workers can contaminate food, utensils and serving ware before these items reach you. Norovirus can also be brought onto the ship via previously contaminated food and water.
• Close quarters and shared spaces – While cruise ships are large with a lot of room to move around, most spaces are shared between guests. And since cruise ships can carry large amounts of people who frequently come in contact with one another, there’s plenty of opportunity for an outbreak.
• High rate of passenger turnover – Because cruise ships usually have new groups of passengers arriving every week or every couple of weeks, there’s constantly new opportunities for a norovirus infection to be introduced onboard.
• Lack of proper cleaning – Since norovirus can live on surfaces (and many sanitizers and cleaning products can’t kill it), it can be difficult to keep norovirus from infecting passengers.

How long norovirus is considered contagious

If you get a norovirus infection, the virus is present in your body – in particular, your stool – before you experience any symptoms. So, you can pass the virus on to others but not as easily as when you start experiencing symptoms.

When your symptoms start, you’re considered contagious from the time you start feeling sick until three days after your symptoms stop. However, the virus can be found for up to two weeks in the stool of some infected people, meaning they’re still considered contagious even if they’re no longer experiencing symptoms.

Although the virus can be found after symptoms resolve, there’s no need to quarantine yourself for any more than three days after your symptoms stop. While it’s not as easily spread without symptoms, you should still take precautions by washing your hands frequently, as that’s the best way to prevent norovirus.

According to the CDC, it is possible to develop immunity against certain strains of norovirus. However, immunity against one type doesn’t mean you’ll be protected against others, so if you’ve been infected with one strain of norovirus before, you can become infected again with a different strain.

Also, it’s not known exactly how long immunity lasts, so it’s possible to become reinfected with the same strain again in the future.

Ways to avoid an infection during a norovirus outbreak

As with any illness, it’s not possible to completely protect yourself from infection. But there are plenty of precautions you can take to lessen your chances of getting sick.

Wash your hands frequently and adequately

Hands are the most common way germs are spread, so proper and frequent handwashing with warm, soapy water is the most effective way to help you avoid a norovirus infection.

Don’t forget to wash your hands after you use the bathroom, help someone else use the bathroom or change a diaper, and always wash your hands before preparing food and eating. Interestingly, hand sanitizer has been shown to be less effective for norovirus, so when there’s an option, always choose traditional hand washing.

Follow best practices for safe food handling and preparation

Since norovirus can also come from food contaminated with the virus, you should always practice safe food handling methods:

• Wash fruits and vegetables before preparing or eating
• Cook oysters, which are at risk for contamination from water, and other shellfish thoroughly
• Keep surfaces clean and disinfected
• Avoid cross contamination
• Don’t touch your face while handling food
• If there’s a chance food has been in contact with norovirus, throw it out
• Do not cook or serve food if you’re sick

Keep the surfaces in your house as clean as possible

One of the reasons norovirus spreads so easily is because it’s hard to kill. The virus can survive on surfaces for up to a month. It’s also less susceptible to heat than other viruses. But the norovirus has its weak spot – bleach. Bleach kills norovirus.

When cleaning and disinfecting your home of norovirus, it’s important to take precautions. The following tips are recommended:

• Use rubber gloves, though it may seem like overkill – Norovirus loves to travel from hand to mouth, so use rubber or disposable gloves when you’re in any area that’s been exposed to norovirus.
• Use bleach or an EPA-approved disinfecting agent – Bleach should be used at the rate of 5-25 tablespoons per gallon of water.
• Wash dishes well – Norovirus can survive in conditions as hot as 145 degrees Fahrenheit. It tolerates higher temperatures than other viruses, so you’ll need to turn up the heat on your cleaning. For many, this will be as easy as setting the dishwasher to “sanitize,” which heats at 150 degrees Fahrenheit.
• Wash and sanitize laundry – If your linens have come into contact with someone who has norovirus, it’s important to sanitize them. Use rubber gloves, handle linens carefully to avoid the airborne spread of germs, and keep contaminated laundry separate from all other linens. Use the longest, hottest cycle for both washing and drying. Wash and dry your laundry at 150 degrees Fahrenheit to kill norovirus germs.
• When in doubt, wash your hands – Again, we cannot stress enough how important proper, regular handwashing is to avoiding norovirus and other illnesses.

Keep away from people and crowded places, especially if you’re sick

If you’re aware of a norovirus outbreak or know someone who has it, isolate yourself as best you can. If you’re sick, stay at home to avoid spreading the illness. If you have to be in close contact with someone who you know is sick, wash your hands frequently and consider wearing a mask for three days after their symptoms have resolved.

During an outbreak, you may want to avoid the norovirus hotspots we mentioned above and others, including hospitals/care facilities, camps, restaurants, schools, cruise ships and airplanes.

Take extra precautions while on vacation

Part of the fun of traveling, whether by cruise ship or other means, is learning new cultures and trying new cuisines. You can have your baklava and eat it too, if you’re careful about norovirus. Stay safe by following these tips:

• Don’t drink tap water – Make sure you only drink bottled water. Also, bring tap water to a rolling boil before making tea or coffee.
• Take it neat – Ice can contain norovirus, so order your drinks without.
• Bring your own soap – Soap dispensers aren’t a given in bathrooms around the world, and you can’t rely on hand sanitizer to do the job when it comes to norovirus.
• Try new foods but don’t take risks – Don’t eat raw or undercooked shellfish, and make sure fruits and veggies are washed.

The risk of getting a nasty stomach bug like norovirus shouldn’t keep you from going on vacation or seeing the world. Exercise a little more caution and you should be fine.

If you’re experiencing norovirus symptoms, stay home and take care of yourself

Norovirus will usually clear up within a few days and doesn’t usually require a trip to the doctor. However, for some people, especially children, older adults and people with compromised immune systems, symptoms might be more severe or linger for longer than a typical norovirus infection.

If you’re experiencing dizziness along with feeling faint or a fainting spell, have someone bring you to urgent care or the emergency room as this can be a sign of dehydration. If you haven’t urinated in six hours or can’t keep fluids down because you’re vomiting, a trip to urgent care for rehydration may be a good idea. If you’ve lost consciousness or your mental status is altered, go to the emergency room.