Norovirus, often called the stomach bug, has returned. Between August 1 and December 11, health officials recorded 268 norovirus outbreaks, with numbers climbing steadily as winter travel increases and more people spend time indoors. The virus triggers stomach-related symptoms such as nausea, vomiting, diarrhea, and abdominal pain or cramping. Some people also develop fever, headaches, and body aches. Although case numbers are not rising as sharply as flu, doctors remain concerned because norovirus spreads extremely easily. Making matters worse, norovirus is difficult to kill. Many of the common precautions used against flu and COVID offer little protection against this so-called winter vomiting bug.How Contagious Is the Norovirus?Norovirus is among the most infectious viruses doctors deal with. “It can tear through a household and then circle back, with people repeatedly passing it to each other,” says Amy Edwards, MD, associate professor of pediatrics at Case Western Reserve University School of Medicine in Cleveland, Ohio, who specializes in infectious diseases. “It also spreads very quickly in crowded, closed settings like cruise ships.”While contaminated surfaces can transmit norovirus, doctors say person-to-person spread is most common. An infected person can pass on the virus even before symptoms appear, throughout the illness, and after they start to feel better, Jennings warns.What to Do If You Get Norovirus?For most people, norovirus symptoms ease within a few days, according to Jennings. However, the illness can be more serious for those with weaker immune systems, including young children, older adults, and people with certain health conditions.If you think you have norovirus, focus on staying well hydrated. Ongoing vomiting can quickly lead to fluid loss and electrolyte imbalance. To prevent nausea from getting worse, Jennings recommends taking small sips of clear fluids like water, ginger ale, or coconut water.Most importantly, seek medical care right away if you become dehydrated or if diarrhea lasts for weeks. Fischer explains that dehydration may cause sunken eyes, less frequent urination, dry skin and mouth, and extreme tiredness.Common Norovirus Symptoms That You Should Be Aware OfNorovirus symptoms often come on suddenly and may include:NauseaVomitingStomach pain or crampsWatery or loose diarrheaGeneral feeling of illnessMild feverMuscle achesSymptoms usually begin 12 to 48 hours after exposure and last for one to three days. Even after recovery, people can continue shedding the virus in their stool for weeks. In some cases, especially among those with other medical conditions, shedding can continue for months. Some people infected with norovirus never develop symptoms at all. Even so, they can still spread the virus to others.Norovirus CausesNorovirus spreads very easily from one person to another. Because it is highly contagious, an infection can pass quickly through homes, schools, or other shared spaces. The virus is released through stool and vomit, and a person can spread it from the moment symptoms begin until several days after they feel better. Norovirus can also survive on surfaces and objects for days or even weeks.You can catch norovirus by:Eating food that has been contaminatedDrinking unsafe or contaminated waterTouching your mouth after your hands have come into contact with a contaminated surface or objectHaving close contact with someone who is infected with norovirusNorovirus is especially hard to get rid of because it can survive extreme hot and cold temperatures and is resistant to many common disinfectants.