Reports of illnesses caused by norovirus are spiking this winter in parts of the world as far-flung as Canada, the United Kingdom and Taiwan this year, prompting food safety advocates to take extra measures to warn the public about the dangers posed by the extremely common virus, which sickens tens of millions of people around the globe every year.
Most of the people who come down with norovirus experience relatively mild symptoms including diarrhea and vomiting. As a result, most experts believe norovirus illnesses are actually underreported; it's rare that someone will get sick enough to seek medical attention, much less for a doctor to think to take a stool or blood sample to positively diagnose norovirus as the cause of the disease. Still, a small subset of those who eat food contaminated with norovirus, mainly the very young and old, become extremely sick, or even die.
In the UK, norovirus cases are expected to be 72 percent more common this winter than last, making them likely to hit a million more Brits than they did in 2012. It's become such a big public health problem that many people are too sick to donate blood, putting a strain on the UK's blood supply.
Food most often gets contaminated with norovirus near the end stages of production, by workers carrying to virus on unclean hands, which means that the recent spate of illnesses can't be classified as an "outbreak" in the same way that, say, a group of peanut butter-related salmonella infections can be. (In other words, no one person or group of people is necessarily responsible for any broad rise in rates.) Yet it's such a pernicious threat to public health that scientists recently invented a "vomiting robot" that will help them study how norovirus is spread.
Though most types of food poisoning are most common in the summer, when warm weather facilitates the rapid growth of bacteria, norovirus is an exception, with about 80 percent of cases cropping up in the winter, when new strains of the virus tend to emerge. Indeed, many of the recent illnesses in the Vancouver area have been linked to a new, particularly virulent strain of norovirus. Certain strains of the virus are often spread to different parts of the world on cruise ships, which have historically been closely associated with norovirus outbreaks.
It's not yet clear whether norovirus illnesses have gotten more common in the United States as well. The Center For Disease Control carefully monitors the incidence of most foodborne illnesses with its FoodNet program, but a spokeswoman told The Huffington Post the it doesn't do so for foodborne norovirus illnesses because they're "too common."
That said, there is evidence that norovirus is hitting the country particularly hard. Many public health officers in the state of North Carolina, for example, have been reporting unusually high rates of the disease, and outbreaks of the virus at a middle school and an assisted care facility, both in California, made headlines this fall after sickening scores of people.
CLARIFICATION: An earlier draft of this post referred to norovirus as a "foodborne pathogen," which was not entirely accurate. Norovirus is spread via traces of fecal matter and vomit from people (including food service workers) who are carrying the disease. This draft also included an incomplete sentence in the third paragraph.
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