Each year in the U.S., about 20 million cases of noroviruses are reported. These are a group of related viruses that cause gastroenteritis, which is inflammation of the stomach and kidneys.

This year, a strand of this virus, called GII.4 Sydney, is especially nasty and spreading across the country. According to the Centers for Disease Control, it sent almost 1 million children under 5 years old to seek medical help in 2009 and 2010.

This particular strain, which is highly contagious, causes several symptoms.

The most common are violent vomiting and severe diarrhea, nausea and stomach pain.

Other less common symptoms may include fever, headaches and body aches.

While this virus is unpleasant, most people get better in two to three days.

As a precaution, there has been an increase in the frequency of cleaning in area school systems. All contact surfaces are being treated with the normal disinfectant twice a day, including surfaces such as door handles, water fountains, light switches, restroom faucets, desks, chair backs, telephones and office counter tops in Newton County.

"Both the disinfectant used throughout the school and the disinfectant used in the cafeteria and kitchens were reviewed by the epidemiologist and both were approved for use on the norovirus and influenza," said Loomans, referring to the epidemiologist from the Gwinnett, Newton and Rockdale Health Department.

The Center for Disease Control estimates that norovirus causes more than 70,000 hospitalizations in the U.S. each year, and leads to about 800 deaths.