Norovirus: What It Is, How We’re Fighting It

Editor’s Note: This is a guest post by Lee-Ann Jaykus, a professor in NC State’s Department of Food, Bioprocessing and Nutrition Sciences, and lead investigator of a $25 million grant from the U.S. Department of Agriculture’s (USDA) National Institute of Food and Agriculture (NIFA) to study human noroviruses.

If you have spent a day or two in bed with vomiting and diarrhea sometime over the last two months, you are certainly not alone. Winter is here, and with it comes so-called “winter vomiting disease.” Your mother might have called it “the 24 hour bug;” others know it as “the cruise ship virus.” Whatever you call it, it’s miserable. And although people rarely die from this illness, most feel like they are going to die!

The culprit is the human noroviruses, a group of viruses now known to be the most common cause of acute gastroenteritis in industrialized countries. These viruses are highly transmissible, moving rapidly through families, schools, day care centers, and elder care facilities. Noroviruses cause classic gastrointestinal symptoms, typically presenting with vomiting (hallmark symptom), diarrhea and abdominal cramps that may or may not be accompanied by fever.  In healthy adults, symptoms usually last 12 to 72 hours. In certain at-risk groups, particularly the elderly, norovirus infection can result in a much more severe disease, with symptoms lasting as long as six weeks. The hospitalization rate is estimated to be 0.03% and the mortality rate is less than 0.1%. Nonetheless, the sheer number of cases make these viruses a leading cause of illness in the U.S., with associated high economic costs and a substantial impact on public health.

How big is the problem? Well, it’s big, with most experts estimating tens of millions of norovirus cases per year in the U.S. alone. Worldwide, these numbers are much higher. There are many reasons why there are so many cases and these viruses are so readily transmitted. For one, noroviruses are shed in very high numbers (in the millions) in the stools of infected individuals; they can also be shed in vomit. They stick around in the environment for long periods of time (probably weeks) and are difficult to inactivate using common disinfectants. People can become exposed to the virus by direct contact with infected individuals, by contact with contaminated surfaces (also called fomites), and by consumption of contaminated food or water. If you are susceptible, only a few infectious viruses can make you sick. No wonder this disease moves through populations so rapidly.

And North Carolina is no exception. Our state is currently experiencing a virtual explosion in norovirus cases. At the time of this writing, eight counties have reported outbreaks, and there will undoubtedly be more to follow. A number of these outbreaks have been in nursing homes. This has prompted state and local health departments across the state to provide advice on how to avoid norovirus illness. Specifically, people who are ill should not go to school or work. In institutional settings such as long-term care facilities, temporary quarantine might be instituted. Because the virus is invisible and can persist on surfaces, frequent thorough hand-washing using soap and warm water is recommended. Do not rely on alcohol-based hand sanitizers; based on the current science, these cannot be relied upon to eliminate noroviruses. Surfaces having come in contact with vomit or stool from infected individuals should be disinfected immediately with diluted household bleach.

And what are we doing about norovirus here at NC State? Well, actually, a lot. Our focus is on foodborne transmission of these viruses. In fact, it now appears that noroviruses are responsible for over 50% of foodborne illness, equating to well over 5.5 million cases per year. And these numbers reflect only those diseases of known etiology; if foodborne disease of unknown etiology were included, these estimates would be staggeringly high. The newly established USDA-NIFA Food Virology Collaborative (called NoroCORE, which stands for Norovirus Collaborative for Outreach, Research, and Education) is working hard to address the problem. This project, funded for the next five years by NIFA, is a collaborative venture between NC State and more than 30 scientists representing academia, industry and government. The team is seeking to improve food safety and public health by tackling the norovirus problem head-on. Together, we will work to increase our understanding of these viruses; develop better diagnostic tests; understand the epidemiological significance of noroviruses; educate producers, processors and food handlers on safe handling and preparation of food; develop control and management strategies to reduce virus contamination in foods along the farm-to-fork chain; and educate our next generation of food safety professionals and consumers alike.

Although we might not have enough time to address this year’s norovirus challenge, in years to come we hope to fight fire with fire. Viruses are crafty devils, but with the best and the brightest minds on-board, we intend to use sound and innovative science to collectively address the problem.  So stay tuned…more to come on NoroCORE and our efforts to ensure the safety of our nation’s food supply.