Norovirus attacks have spread among students and families and are even shutting down some U.S. schools. Highly contagious, the virus is known to strike a significant percentage of people in hospitals, schools and cruise ships.
Also dubbed the winter vomiting disease, the stomach bug or stomach "flu," there are reports that the disease is on the rise this winter season, The Wall Street Journal reports.
The Eastern Howard School Corporation of Indiana closed on Jan. 24 after 27 percent of the elementary school children were struck by the virus on Jan. 20. Previously, St. Charles East High School near Chicago shut down for two days in early January when 800 out of its student body of 2,500 students fell ill due to norovirus.
Rhode Island's Globe Park Elementary School of Woonsocket also closed for a couple of days in early January due to an outbreak that affected 100 of its 513 students.
The rise in frequency is standard for the season, says the Center for Disease Control and Prevention. An average of about 19 to 21 million cases of the virus arise every year, the agency said.
Symptoms include vomiting, nausea, stomach pain, diarrhea and sometimes body aches and fever.
Dehydration can result from the sickness that typically lasts for a few days. In 61 percent of cases, the disease is spread through close contact or contaminated surfaces.
Norovirus is responsible for nearly half of all outbreaks of food-borne illnesses.
Though dubbed the stomach "flu," the virus is not related to influenza, Today.com reports.
The disease notably struck 700 people aboard the Royal Caribbean cruise ship Explorer of the Seas in January 2014.
Each year, norovirus causes 70,000 people to go to the hospital. Up to 800 of those die, mostly senior citizens who become dehydrated.
Researchers have found that the violent vomiting that is caused by the virus sends small particles of the vomit into the air, which readily infects others.
"We think that there's a at least a million particles released in a vomiting event and maybe more," said Lee-Ann Jaykus, a North Carolina food science investigator.
Norovirus is especially hard to wash away. It takes about 30 seconds of thorough scrubbing with hot water and soap to wash away the tiny particles of virus.
"Imagine you have a food handler who uses the bathroom and they haven’t washed their hands thoroughly," said Allison Aiello, who studies the spread of the disease at the University of North Carolina.
"They can end up preparing a salad for the diners that evening and end up infecting a lot of people because the food isn’t cooked."