Know all about Norovirus

Sonya’s illness came on so suddenly that she threw up in the hallway near the door of the bathroom. Her vomiting slowed later that Friday but was followed by stomach cramps and diarrhea through most of the weekend.

By Monday, Sonya was feeling much better, but by that time her illness had spread, affecting at least 20 others on her floor of the university dormitory.

“Gastroenteritis, an inflammation of the stomach and intestines, is often mistakenly called “stomach flu,” even though it has no relation to influenza, a respiratory illness. However, when gastroenteritis is caused by norovirus, as it often is, it is every bit as contagious as any respiratory illness,” expressed Dr. Cathy Houle.

Norovirus is the new official name for a group of viruses often referred to as Norwalk or Norwalk-like viruses. The latter name refers to Norwalk, Ohio where a large outbreak occurred among school children in 1968. Norwalk virus also gained national attention after it was identified as the cause of similar large outbreaks on cruise ships.

Stomach and intestinal illness can be caused by bacteria or parasites but most commonly by a virus. And norovirus accounts for more than half of all food-borne cases of gastroenteritis in the United States. An estimated 23 million Americans are infected each year, according to the Centers for Disease Control.

In addition to nausea, vomiting, cramping and diarrhea, symptoms include a mild fever, chills, headache, muscle ache and general fatigue. Children are more likely than adults to have vomiting. Symptoms usually come on suddenly but are gone within one or two days with no long-term health effects.

The greatest danger is dehydration, caused by excessive loss of water from the body. In children and in older adults, this may pose a serious health problem.

Outbreaks Spread Quickly

Because norovirus is so contagious, the illness is rarely limited to one person or even a small group who ate the same contaminated food. Outbreaks of norovirus gastroenteritis are common in group settings such as schools, nursing homes, cruise ships, banquet halls and summer camps.

Unlike influenza or cold viruses, which are transmitted through the respiratory passages (coughing, sneezing, nose blowing), noroviruses are typically transmitted through the fecal-oral route.

You may eat food at a restaurant or street stall that has been contaminated with a fecal virus. Once you get sick, you carry the virus on your hands and your person, passing it along to others who are nearby or who merely touch the same door knob you touched.

Infected persons are contagious from the time they start showing symptoms until at least three days–and sometimes as long as two weeks–after they start feeling better. During this period, it’s easy for them to infect others unless they are careful about hand washing and other hygiene measures. Without special precautions, it’s estimated that one infected person will pass the disease to an average of 41 others.

In addition, as many as 30 percent of infected persons never experience symptoms, according to some studies. These carriers, too, presumably can spread a trail of infection everywhere they go unless they follow good hygiene practices. And since there are multiple strains of the virus, repeat infections are common. Virtually anyone is vulnerable to being infected.

Once an outbreak starts, particularly in an institutional setting such as a school or nursing home, it becomes difficult to control. In one long-term residential treatment center, three outbreaks occurred in 2007, the latter lasting 63 days.

The vomit of a sick person is infectious and must be cleaned immediately with disinfectant. In addition, there is fairly good evidence that the virus can be transmitted through small droplets emitted by the vomit and carried in the air.

In one institution, a high percentage of workers who cleaned the vomit of patients later got the illness themselves, even though they wore gloves and gowns. The best protection, it seems, includes face masks as well. Even so, the droplets may form on objects in the environment.

Preventing the Spread

“Preventing norovirus illness starts with safe food handling practices at all times, but with enhanced vigilance and attention to hygiene once an infection has occurred. Outbreaks have started with foods such as raspberries that were contaminated at the site of harvest. Public health officials stress that you should wash fresh fruits and vegetables before eating,” warns Linda Nudell, LRD, CDE, West River Food and Nutrition Services Manager.

“The virus is durable, however, and has been known to survive freezing and steaming. Food can be contaminated by a person at any stage, and that’s why it’s important to wash hands with soap before starting food preparation; after handling meat, eggs or other potentially contaminated products, and after going to the toilet.

It’s important too to avoid contaminating your own food, at home or when eating out. Wash your hands before preparing food and before eating, particularly after going to the toilet or changing a baby’s diapers,” cautions Nudell.

When gastroenteritis occurs to anyone in your family, be sure to clean and disinfect all surfaces that could be contaminated, using a bleach-based household cleaner. Be particularly vigilant in areas where vomiting and diarrhea have occurred. Remove and wash the patient’s clothing with hot water and soap.

Following a bout of gastroenteritis, a person should stay home from work or school and refrain from cooking or handling food for others for at least three days after recovery.

Most Americans experience gastroenteritis from time to time, and norovirus is often involved. While vomiting and diarrhea are never fun, long-term health effects are rare as long as you replace the fluids that are lost. Warning signs of dehydration include sunken eyes, dry mouth and tongue, decreased urine output and, sometimes, lightheadedness when rising from a sitting or lying position.

But while the illness itself poses little threat, norovirus is highly contagious, more infectious than any other virus that has been studied. Care must be taken to avoid multiplying the suffering.

After Eight Hours

Replace fluids slowly -- introduce bland foods once vomiting has stopped. Adults should stick with water or ice chips. For infants, alternate small amounts of an electrolyte solution such as Pedialyte with breast milk or formula. Children age two or older can drink half-strength sports drinks like Garorade or de-fizzed 7-Up. Popsicles are another way to slowly introduce liquids to a sensitive digestive tract.

Easy-to-digest foods like bananas, saltine crackers or toast may be slowly introduced.

If vomiting lasts more than two days and/or there is the appearance of blood in diarrhea or vomit, or you have any other concerns, contact your doctor.

11/12/2009