Gibson Answers Common Questions About Norovirus

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Kristen Gibson

FAYETTEVILLE, Ark. – The norovirus has forced temporary closings of several schools in the Northwest Arkansas area. Kristen Gibson, an assistant professor of molecular food safety and microbiology in the Dale Bumpers College of Agricultural, Food and Life Sciences, is an expert on the virus.

Gibson earned her bachelor’s degree in microbiology and molecular biology from the University of Central Florida, and her doctorate in environmental health sciences from Johns Hopkins University.

Gibson has studied the virus for 10 years and provided answers to several common questions.

What is norovirus and what are its symptoms?

Norovirus is a virus that causes acute gastrointestinal illness, basically diarrhea and vomiting. The most common symptom associated with norovirus is projectile vomiting. Normally symptoms will begin with nausea and stomach cramps followed by vomiting and very watery diarrhea. Those who are infected rarely have a fever and usually symptoms last only 24 to 48 hours. 

It’s not the flu, but how is it different?

Sometimes norovirus is referred to as the ‘stomach flu’ and this is a common misnomer. This happens because the norovirus season peaks at the same time as the flu. However, norovirus and influenza viruses are very different. Norovirus causes a gastrointestinal illness whereas the flu causes a respiratory illness. In addition, vomiting and diarrhea are rarely associated with the flu with some exceptions for young children. It’s possible for someone to have both the flu and norovirus at the same time.

Several area schools have had to temporarily close. Why do schools seem to be a breeding ground and how does the virus spread?

Schools, and other ‘closed’ settings such as cruise ships, hospitals and college dormitories are susceptible to norovirus outbreaks because they have a large number of susceptible people and once the virus is introduced, it can spread rapidly. The rapid transmission is primarily caused by:

1. Shared facilities such as bathrooms, classrooms and cafeterias where people interact;
2. The low amount of virus required for illness (only 100 virus particles are needed);
3. The ability of norovirus to remain infectious on surfaces for several days and even weeks.

Overall, norovirus is spread from person-to-person, ingestion of contaminated food and water, and contact with contaminated surfaces.”

What is the best way for someone to stay protected?

“The best way to protect yourself is to wash your hands frequently with soap and warm water, not hand sanitizer; to avoid physical contact with people who have been sick; and disinfect ‘hot spots’ – any area where someone has become sick – with a chlorine bleach solution. The best ratio is 1.5 cups of bleach per one gallon of water.

What is the best way to treat it and care for someone who has it?

Unfortunately, there is no treatment for someone who is sick with norovirus. Because it normally runs its course within 24 hours, the most important thing you can do is stay hydrated to avoid complications related to dehydration. This is probably counter intuitive to those with the virus because the last thing you want to do is put something else in your stomach, but it is very important to keep fluids in your system. With respect to taking care of someone with norovirus, you should try to avoid physical contact, and if there are multiple bathrooms available, you should designate one bathroom for that person and everyone else should use the other bathroom. In addition — and this may seem harsh —the bathroom used by the person with norovirus should be disinfected with chlorine bleach solution and the best candidate for the job is the person who is or was actually sick.

If you get it, how long do you typically carry it?

One of the reasons norovirus can spread rapidly through a group of people is that you start shedding the virus in very high numbers even before you show clinical symptoms. Obviously when you are having symptoms of vomiting and diarrhea, you will be shedding copious amounts of the virus (100 billion viruses per gram of diarrhea or 100,000 viruses per gram of vomit). However, after the symptoms subside, you can carry this virus for up to three weeks and still be infectious to people who have not been exposed. This is a critical time to practice good hygiene.

How can you take precautions to keep from getting it again?

Once you have norovirus, your immunity to that particular strain with which you were infected will last around three-to-six months and sometimes up to one year. However, we know of 26 genetic clusters, or groups, of norovirus that can infect humans, and within each of those groups there are different strains. This is important because immunity is specific at the strain level, which means you can become ill due to exposure to a different strain of norovirus even if you were just sick. Luckily, there are dominant strains that circulate each year and the likelihood of becoming ill due to a different strain of norovirus is probably low, though that depends on the individual person – for example, if you travel a lot, or visit relatives in a nursing home or hospital.