Norovirus cases are on the rise in the US: Here's what you should know about symptoms

Norovirus cases are on the rise in the U.S. especially in the Northeast, the Centers for Disease Control and Prevention said.

Norovirus, sometimes referred to as a "stomach flu" or "stomach bug," is a common virus that's highly contagious and spreads through tiny particles of feces or vomit and results in gastrointestinal symptoms. Many different noroviruses can cause illness, the CDC said.

“Norovirus is a very contagious virus that causes vomiting and diarrhea. Anyone can get infected and sick with norovirus,” the CDC explains.

According to the most recent CDC data, more than 12% of tests for the virus came back positive in the week ending on Feb. 17. The week before that a little more than 11.5% of tests came back positive.

The Northeast has seen a higher rate of norovirus cases. During the week ending on Feb. 24, more than 16% of tests came back positive, CDC data shows. Positivity rates in the Northeast have been more than 13% for the past month.

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What are the symptoms of norovirus?

According to the CDC, norovirus is the leading cause of vomiting and diarrhea, and foodborne illness in the U.S.

The virus causes acute gastroenteritis, an inflammation of the stomach or intestines. The most common symptoms are:

• Diarrhea.
• Vomiting.
• Nausea.
• Stomach pain.

Less common symptoms include:

• Fever.
• Headache.
• Body aches.

The symptoms typically start 12 to 48 hours after being exposed to the virus, and most people will get better within 1 to 3 days. However, they may still be able to spread the virus for a few days after their recovery, the CDC said.

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How is norovirus transmitted?

Anyone can fall ill with norovirus. The virus however is not related to the influenza virus that causes the flu.

"People of all ages can get infected and sick with norovirus, which spreads very easily and quickly," the CDC said.

Someone can become sick with the virus if they accidentally get tiny particles of feces or vomit in their mouth from someone infected with the virus, the CDC said. Someone sick with norovirus could shed billions of microscopic norovirus particles, but it only takes a few particles to make someone sick.

The CDC says someone can get norovirus by:

• Having direct contact with someone with norovirus, such as by caring for them, sharing food or eating utensils with them, or eating food handled by them.
• Eating food or drinking liquids that are contaminated with norovirus.
• Touching surfaces or objects contaminated with norovirus and then putting your unwashed fingers in your mouth.

How does norovirus spread?

Norovirus can spread through contaminated food or water. When someone with norovirus touches food with their bare hands, or food is placed on a surface that has fecal or vomit particles on it, that could lead to infection. Additionally, the virus could spread when tiny drops of vomit from a person with norovirus spray through the air and land on the food.

Additionally, food that is grown with contaminated water could also lead to the spread of norovirus. Water can become contaminated from a septic tank leak, when someone with norovirus vomits or defecates in water, or when water isn't treated properly with enough chlorine.

When is norovirus contagious?

The CDC says people are most contagious when they are showing symptoms of a norovirus infection. Infected individuals can also be contagious in the initial days after they recover from an infection, but could also remain contagious for more than two weeks after they feel better.

How to prevent the spread of norovirus

The CDC recommends several things to prevent getting sick or spreading the norovirus, including:

• Washing your hands well with soap and water. The CDC added that hand sanitizer does not work well against norovirus. 
• Cleaning and disinfecting surfaces with bleach.
• Washing laundry in hot water.
• Do not prepare and handle food or care for others when you are sick and for at least 2 days (48 hours) after symptoms stop.
• Washing fruits and vegetables well.
• Cooking oysters and other shellfish thoroughly to an internal temperature of at least 145 F.
• Routinely clean and sanitize kitchen utensils, counters, and surfaces.

Sarah Al-Arshani covers breaking and trending news for USA TODAY. Reach her at salarshani@gannett.com.