What You Need to Know About Norovirus
Stomach flu has been making the rounds lately. I have to start by dispelling a common misconception people have that all types of “flu” are the same. “Stomach flu” is not caused by the same viruses that cause respiratory illnesses. Flu shots, given this time of year to help prevent respiratory influenza, will not protect you against viruses affecting the gastrointestinal tract.
Noroviruses are the number one cause of acute viral gastroenteritis in the United States with an estimated 21 million cases per year. These annual infections lead to 70,000 hospitalizations and 800 deaths. The name norovirus is derived from a virus that was first identified as the cause of an outbreak of illness in a school in Norwalk, Ohio in 1968.
Noroviruses are a very sturdy group of viruses, able to withstand freezing and temperatures as high as 140 degrees Fahrenheit. They can survive steaming when cooking shellfish and are even resistant to the levels of chlorine found in municipal drinking water.
Typical symptoms of norovirus infection include the sudden onset of nausea, vomiting, diarrhea, and abdominal pain/cramping. Diarrhea is particularly common in children. These symptoms can lead to dehydration, especially in the young and elderly.
Noroviruses are the most common pathogen responsible for outbreaks of gastrointestinal illness on cruise ships. The viruses are highly contagious and spread rapidly in close quarters such as day cares, schools, nursing homes, hospitals, restaurants and ships. The vomit and diarrhea of norovirus sufferers can contain billions of viruses. Ingesting as few as 100 of these viruses can result in illness.
The virus is spread through exposure to the vomit and stool of an infected person and also through contact with contaminated surfaces or clothing/linens. Contaminated food (particularly shellfish) and water can also cause infection. Spread of the virus in schools and daycares is particularly common through shared toys, books, and utensils. Infected persons who prepare food also frequently spread the virus.
The incubation period from exposure to symptoms is between 24 and 48 hours. Most people are ill for one to two days, but they are contagious from the time they fall ill until at least three days after their symptoms subside and sometimes up to two weeks later. It is therefore very important to keep children out of school for at least three days following their improvement and for anyone doing food preparation to avoid work for that time period as well.
Treatment of norovirus infection is symptomatic – avoid dehydration and take medication for fever. Usually water is adequate the first day or so, but if the illness persists, we usually recommend taking an oral rehydration solution like Pedialyte. A simple recipe for rehydration solution is to add two level teaspoons of salt and eight heaping teaspoons of sugar to a two-liter bottle of water. Intake should be monitored, especially in children, who should take small sips rather than allowing them to gulp the fluid down.
The key to preventing the spread of norovirus is proper hygiene, particularly hand washing (which we all should be doing anyway). Anyone who has norovirus-like symptoms or is taking care of someone with suspected illness should wash their hands regularly for 20 seconds using warm water & soap. This is especially important after using the toilet or changing diapers as well as prior to preparing food. Vegetables, fruits, and shellfish should be thoroughly washed before cooking.
Any surfaces or items that have been in contact with an infected person should be cleaned with bleach water made by mixing one part bleach with nine parts water. The solution should be left in place for 10 – 20 minutes. Clothing or linens that have been in contact with an infected person should be washed in hot water for the maximum cycle length and dried in a dryer.
Most people get over norovirus illness without complications. If a person appears dehydrated, lethargic, or complains of severe abdominal pain, he or she should contact their doctor.
Dr. John Roberts is a retired member of the Franciscan Physician Network specializing in Family Medicine.