I was sitting on the toilet this morning, answering e-mail while trying to hurry things up and get Sorenne to school, and I responded to an e-mail from a reporter at msnbc by saying, “don’t take reusable grocery bags to the bathroom.”

I could have said, don’t take groceries to the bathroom: I’ve seen it.

In 2010, seven of 17 players on a youth girls soccer team in Oregon fell ill while attending an out-of-state tournament. But, as investigators discovered, none of the players had been in direct contact with the index case — the first girl to get sick.

Investigators were stumped.

Kimberly K. Repp, PhD, an epidemiologist with the Washington County Department of Health and Human Services in Hillsboro, Ore. said, "We conducted a very extensive interview; it’s called a shotgun interview, where we ask about every possible food exposure. There are over 800 questions on the questionnaire.”

That helped the researchers figure out what the sick people ate and what the healthy people didn’t eat.

According to a new study in today’s Journal of Infectious Diseases, authored by Repp and Bill Keene, all the girls who got sick had eaten cookies during a Sunday lunch. By Tuesday, those cookies, along with much of the other foods the girls had eaten during their stay, had been thrown away.

The connection turned out to be a reusable grocery tote bag filled with the cookies and other food items like chips and grapes that had been sitting on the floor of the bathroom where the first girl had repeatedly gotten sick.

Investigators swabbed the bag two weeks after the first person fell ill. DNA tests turned up copies of the same strain of norovirus that had infected the girls.

"This is the first-ever reported case of transmitting this virus with an inanimate object, basically," Repp says.

The first sick girl said she never touched the bag. So how did the virus get there?

Experts say viral particles likely floated over from the toilet.

All the girls had traveled in private automobiles, shared hotel rooms, and eaten at local restaurants. Eight cases were identified, including the index patient who was presumably infected prior to the trip. There was no direct contact between the original patient and her teammates after her symptoms began; before her overt symptoms began she left her room and moved in with a chaperone. The girl subsequently began vomiting and having diarrhea in the chaperone’s bathroom. The outbreak affecting the rest of the team began several days later; they were exposed by handling a bag of snacks that unfortunately had been stored in the hotel bathroom. Virus aerosolized within the bathroom likely settled onto the grocery bag and its contents. Matching viruses were found on the reusable shopping bag two weeks later.

The investigation confirmed the great potential for contamination of surfaces in norovirus outbreaks on cruise ships, in nursing homes, and in other group settings.

"While we certainly recommend not storing food in bathrooms," the authors note, "it is more important to emphasize that areas where aerosol exposures may have occurred should be thoroughly disinfected; this includes not only exposed surfaces, but also objects in the environment" that could become contaminated and spread infection. The authors point to some of the practices that can be put in place to limit outbreaks caused by such indirect contact, including disinfection of affected areas and the use of multiple bathrooms with one dedicated for use by those who are sick.

In an accompanying editorial, Aron J. Hall, DVM, MSPH, of the Centers for Disease Control and Prevention, notes that noroviruses "are perhaps the perfect human pathogens," causing an estimated 21 million cases of acute gastroenteritis annually in the U.S. alone. The investigation of this outbreak, as reported by the study authors, "provides a fascinating example of how a unique exposure and transmission scenario can result in a norovirus outbreak."

"That certainly is an area of active research, involving the dynamics of vomiting, and how are particles dispersed when somebody vomits. There is a limited range, for sure, but exactly how far it is and what the level of risk is 10 feet away or 30 feet away. Certainly, in this case, it was plenty close to allow the virus to float over onto the bag," says Aron J. Hall, DVM, MSPH, of the CDC’s division of viral diseases.

Some info:

1. Norovirus can spread infection through contact with surfaces and objects contaminated by aerosolized particles.
2. Noroviruses are highly contagious, even in low concentration, and the viruses spread efficiently from feces and vomit by direct and indirect contact.
3. Noroviruses are the leading cause of endemic diarrheal disease across all age groups, the leading cause of foodborne disease, and the cause of half of all gastroenteritis outbreaks worldwide.
4. Whenever possible, ill persons should use a separate bathroom to reduce the potential for spread of the virus. Notify family members or cleaning staff about the need for thorough disinfection of surfaces.