Norovirus is back (and in record numbers): Here's what you need to know.

Protecting yourself and your kids from a very nasty GI virus that is stronger and tougher than the average stomach bug.

In my beginning of the week reflection/preview I mentioned this piece in The New York Times.¹ Written by Emily Schmall, it talks about the Norovirus a, “highly contagious virus, which sickens an estimated 19 to 21 million people nationwide each year, can cause sudden and unpleasant gastrointestinal symptoms.”

Some recent outbreaks have been linked to food, such as raw oysters (the FDA has encouraged consumers to avoid these for the time being). But it is something that can be spread through much more universal means, and this is what I think is worth knowing about for parents who want to protect their kids and themselves.

Dr. William Schaffner, a professor of infectious diseases at the Vanderbilt University School of Medicine, said there are two characteristics that make norovirus “extraordinarily” contagious: It’s easily transmissible, and it’s hardy enough to survive on surfaces for days or even weeks. A person can contract norovirus from contact with an infected person or from contaminated food, water or surfaces.

Dr. Schaffner recalled a case in Tennessee in which a member of a bridge club became sick with norovirus and vomited in the parking lot. Everyone else at the table then became infected. He said that public health investigators later found norovirus on the playing cards.

A person sick with norovirus can shed significant amounts of the virus, and it doesn’t take much to infect someone else. Because of this, the virus thrives in crowded, indoor spaces like cruise ships, nursing homes, schools and day care centers, experts said.

How does it get into the food supply?

Contaminated water also poses a threat: Untreated sewage can pollute water, which then spreads norovirus into the food supply through irrigation, said Donald W. Schaffner, a food microbiologist at Rutgers University who is not related to Dr. Schaffner of Vanderbilt.

Norovirus outbreaks are also frequently linked to shellfish like oysters and mussels, which eat by filtering water and can end up carrying concentrated amounts of bacteria or viruses in their flesh, Dr. Schaffner of Rutgers added.

Now that we know some of the grim details, how can we avoid it?