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Norovirus: What you should know

Reports from Yosemite National Park in California reveal that at least 170 visitors and personnel have come down wih a mysterious intestinal ailment. Lab studies have identified a virus called “Norovirus” as the culprit in at least two cases, with most of the rest also consistent with the illness.

Hearing about this incident struck a chord with me personally. I often write about various medical issues in austere settings, like trauma or epidemics.  It doesn’t, however, take a survival scenario to suffer from a serious infection. Just taking a drink from a clear mountain stream could make you ill if contaminated with the wrong microbe.

Many years ago, I converted to positive for Tuberculosis during my E.R. work with Cuban refugees during the 1980 Mariel boatlift. I still carry two small (walled-off) lung nodules on X-ray, even after months of multi-drug therapy.

In 2017, we had a personal experience with norovirus, not in Yosemite, but in Manhattan. My wife Amy, a nurse practitioner, contracted acute gastroenteritis, also known as the “Stomach Flu”.

When this infection hits you, it makes even the healthiest individual miserable.  Amy required an urgent care visit, no small issue in a strange and heavily-populated city. Looking at statistics, we found that she was just one of nearly 2 million outpatient visits caused by norovirus every year.

Amy after her recovery

Norovirus is the most likely cause of viral gastroenteritis in humans. It was originally called Norwalk Virus, after the area where it was first identified in the 1960s. Since then, it’s been blamed for 50-60% of all gastroenteritis in the U.S.

Worldwide, there are more than 200 million cases of norovirus infection a year. It affects people of all ages, but it’s particularly dangerous in the elderly, the very young, and those with weakened immune systems. Winter is the most common time for outbreaks.

Norovirus is very contagious (just 5-20 viral particles can cause illness) and is easily transmitted through contaminated food or water, close personal contact, and by air droplets from vomit, contaminated work surfaces, and even toilet flushes. Infection can be passed from person to person for a time even after apparent recovery.

Here’s how contagious the Norovirus is: In one outbreak reported in 1998, 126 people were dining at a restaurant when one person vomited onto the floor. Despite a rapid cleanup, 52 out of 126 fell ill within three days. More than 90% of the people who dined later at the same table reported symptoms. More than 70% of the diners at nearby tables got sick as well; at a table on the other side of the restaurant, the infection rate was still 25%.

Norovirus is a hardy microbe, and is known to survive for long periods outside a human host. It can live for weeks on countertops and up to twelve days on clothes. It can survive for months in still water. Disinfectants containing chlorine, however, like bleach will quickly eliminate it, as will exposure to high heat.

The symptoms of the stomach flu include nausea and vomiting, watery diarrhea, and (sometimes severe) abdominal pain. These usually appear within 12 to 48 hours of exposure. Along with this, muscle aches, headache, and fever may be seen. Luckily, life-threatening illness is rare, with dehydration being the main danger in those infected with the virus.

Unlike some viruses, immunity to norovirus is only temporary, maybe six months, after recovery. Therefore, it is possible to get it more than once.

Outbreaks of norovirus infection often occur in closed spaces such as cruise ships, nursing homes, schools, camps, and prisons. Shellfish, such as oysters, and salad ingredients are the foods most often implicated in norovirus outbreaks. In Amy’s case, it might have been a kiosk advertising “the World’s Best Hot Dogs”.

As with most viruses, there is no cure for norovirus infection. Antibiotics are ineffective; they are meant to kill bacteria, not viruses. Treatment involves the prevention of severe dehydration. In developed countries, the ready availability of intravenous fluid replacement helps treat victims and saves lives.

Dehydration can be noted by these symptoms:

  • Dry mouth
  • Decrease in quantity or dark color of urine
  • Dizziness when standing up
  • Decreased elasticity of skin (it “tents” when pulled up)
  • No tears when crying or unusual irritability in infants

Using antidiarrheal meds like loperamide (Imodium) and anti-vomiting drugs like Ondansetron (Zofran) may also help prevent the loss of body fluids.


Norovirus may not have a cure, but prevention is possible. To decrease the chance of norovirus infection:

  • Wash your hands frequently with soap and water (norovirus is relatively resistant to alcohol), especially after using the restroom or handling food. Be especially sure to do this for 2 full weeks after becoming infected (yes, you can be contagious for that long).
  • Wash food before cooking; cook shellfish thoroughly
  • Frequently disinfect contaminated surfaces with a bleach solution (the EPA recommends 5-25 drops of bleach per gallon)
  • Keep sick individuals away from food preparation areas
  • Avoid close contact with others when you are sick, and don’t share utensils or other items
  • Wear disposable gloves while handling soiled items
  • Immediately remove and wash clothes that may be contaminated with vomit or feces. Machine dry if possible.

It may be difficult to completely eliminate the risk of becoming ill from contaminated food and water, but careful attention to hand and food hygiene will go a long way to prevent, not only Norovirus, but many other infections as well.

Joe Alton, MD

Joe Alton MD

A full medical kit is a part of an important defense against both natural and man-made disasters. Become more medically prepared with a kit from Nurse Amy’s entire line at

Hey, don’t forget to check out our entire line of quality medical kits and individual supplies at Also, our Book Excellence Award-winning 700-page SURVIVAL MEDICINE HANDBOOK: THE ESSENTIAL GUIDE FOR WHEN HELP IS NOT ON THE WAY is now available in black and white on Amazon and in color and color spiral-bound versions at

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