(Washington DC) – Department of Health Director Gregg A. Pane, MD, on Friday said the outbreak of noroviruses among Catholic University students has been contained, and urged the practice of universal health precautions for those who may have come into contact with those affected.

The viruses are passed primarily when an infected person spreads microbes either by preparing food or sharing plates or utensils. But noroviruses also can live on doorknobs, toilets and other inanimate objects and surfaces for a time.

Because it takes very few viral particles to sicken someone -- only about 100, compared to the millions of salmonella particles needed for a person to fall ill -- noroviruses are especially easy to spread. They generally don't spread through the air, but when patients are violently ill they can vomit in such a way that it creates an “aerosol” effect, Dr. Pane said.

“It's basically a virus that has been recognized a long time with the appearance of diarrhea,” he said. “Most people who fall ill will feel nauseated and miserable for 24 to 48 hours, then quickly recover.”

Noroviruses, which are commonly and misleadingly known as the stomach flu, are highly contagious and cause violent and sudden bouts of diarrhea and vomiting. Outbreaks generally show up where lots of people share crowded common spaces, including college dormitories, cruise ships, summer camps, and nursing homes.

They are believed to be responsible for roughly half of all food-borne illnesses in the United States, although they're far less serious than their bacterial cousins, such as E. coli and salmonella.

More than 50 students had varying degrees of illness and experienced symptoms that lasted six to 12 hours. Most were treated at the campus student health services center and only those who felt sick after hours went to emergency rooms.

Preliminary tests on the sick students by the District of Columbia Health Department showed the presence of norovirus, which is highly contagious but rarely serious.

Health officials said contact may be limited by following these preventive steps:

• Frequently wash your hands, especially after toilet visits and changing diapers and before eating or preparing food
• Carefully wash fruits and vegetables, and steam oysters before eating them
• Thoroughly clean and disinfect contaminated surfaces immediately after an episode of illness by using a bleach-based household cleaner
• Immediately remove and wash clothing or linens that may be contaminated with virus after an episode of illness (use hot water and soap)
• Flush or discard any vomitus and/or stool in the toilet and make sure that the surrounding area is kept clean