Here's what you need to know about norovirus

Jan. 25, 2013, 10:41 a.m.

Uncooked food, like salad, is more likely to transmit norovirus than something that's been prepared at high temperatures. (Jack Lyons/Flickr Creative Commons)

Although influenza is leveling off across the nation, the U.S. isn't quite in the clear yet, thanks to a little bug known as "norovirus."

Federal health officials announced on Thursday that a form of norovirus known as "Sydney strain" – a nod to the fact that it was first identified in Australia last year – has caused more than 140 outbreaks in the U.S. since September.

The virus causes gastrointestinal illness among both adults and children. Put another way, norovirus is a nasty stomach bug.


Dr. Kalvin Yu, the regional infectious disease lead for Kaiser Permanente Southern California, described the unpleasant symptoms.

"Usually in children, it presents [itself] with severe vomiting for at least 24 hours," he said. "They can also get diarrhea after the vomiting course, so it's almost like a two-phase process."

Adults will experience "similar symptoms" as well as potential abdominal cramps, he said, although "it's usually a bit more mild."

Norovirus can put children, the elderly and those with other underlying conditions at particular risk, though, because the extreme expulsion of bodily fluids can cause severe dehydration. Those two populations, said Yu, are "at risk for higher morbidity and morality" when they get dehydrated.

"[Children] don't verbalize that they're thirsty and they feel too sick to communicate," he added.

The virus is extremely contagious, and is usually transmitted by food or water that's somehow been contaminated. There's also evidence that droplets from the vomit of someone with norovirus can "aerosolize" and travel pretty far – so if those germs land on a doorknob, and you touch that doorknob, and then touch your face, you could soon be sick.

"The problem with norovirus is, unlike other viruses, you really only need a small amount to get sick," said Yu. "With other viruses, you need a big exposure count to really feel it."

On top of that, the virus is RNA-based, meaning it has "the propensity to mutate," Yu said. That means it's not like chicken pox, where you get it and you're immune to it for most of your life. You can catch one strain, then catch a different strain later on.

It also doesn't help that norovirus' run overlaps with two other viruses making their way through California: the flu and respiratory syncytial virus.

"The problem is that some of the symptoms overlap between the three," said Yu. "So for instance, you can have a fever and stomach discomfort with all three." That makes diagnosis more difficult, he explained.


There are a few preventive measures one can take, said the doctor – the most important of which is keeping your hands clean.

"If you're just going shopping and you open a door with a doorknob, it's not that intuitive to wash your hands before you touch your face," said Yu. "That's really the key to preventing spread."

Using bleach-based cleaners around the house can also keep the home germ-free. High temperatures tend to inactivate norovirus, so a cooked steak is less likely to be contaminated than something from a salad bar, said Yu, and a cup of piping hot tea is less likely than a cup of water to carry virus.

There's no vaccine or treatment for norovirus, but the sickness often subsides on its own after a few (admittedly awful) days at most. Yu said as of now, it doesn't look like it'll become an epidemic.

Photo by Jack Lyons via Flickr Creative Commons.

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