By Gretchen Goetz at Food Safety News:

The top left corner of the menu at Jimmy John’s restaurants jokingly tells customers that the store was established “to add to students GPA and general dating ability.”

But an investigation into the cause of a foodborne illness outbreak in Northwest Indiana shows that the sub shop may have been responsible for making 60 area residents un-datable, at least for a few days, while they suffered from nausea, vomiting and indigestion.

Last Friday, after three trains collided near Valparaiso, the Red Cross provided meals for rescue workers at the scene of the crash, and some of that food was catered by the local Jimmy John’s outlet. On Sunday, the Porter County Health Department received reports that about 20 of the workers had fallen ill.

By Monday, people who had not been at the crash site began to report similar symptoms. All those victims had recently eaten at the same Jimmy John’s, prompting the Health Department to declare the restaurant the possible source of an outbreak of foodborne illness.

And while media reports identified the illness merely as “gastroenteritis,” an inflammation of the stomach and intestines, the Indiana State Department of Health (ISGH) told Food Safety News that state labs identified norovirus as the pathogen responsible for the outbreak.

The Valparaiso Jimmy John’s restaurant – located on Lincolnway – has cooperated fully with the investigation. It briefly closed its doors to sanitize the facility, and reopened by Wednesday afternoon. Staff from other locations filled in for regular workers, who are currently being tested for norovirus.

And while food served by Jimmy John’s appears to be the likely source of the illnesses, “the Indiana State Health Department of Health is looking at all food items served [at the scene of the train crash],” and is not entirely ruling out other food sources yet, ISDH told Food Safety News in an email Thursday.

If the sub shop is indeed confirmed as the source of these sicknesses, it would not be a first for the chain, which since 2008 has been implicated in 3 foodborne illness outbreaks, sickening at least 168 people. All of the previous incidents were linked to raw sprouts.

As far as the food responsible for the latest outbreak, though, “We’re still investigating this and we have not identified an exact vehicle,” said ISDH.

No one has been hospitalized, as far as health officials are aware. All those ill with vomiting and diarrhea are expected to recover fully.

Noroviruses, which cause more than half of all foodborne illness outbreaks, are transmitted primarily through the fecal-oral route, and fewer than 100 norovirus particles are said to be needed to cause infection. Transmission occurs either person-to-person or through contamination of food or water. Foodborne norovirus transmission can occur when food is contaminated by an infected food handler.

According to Centers for Disease Control and Prevention estimates, more than 5,400,000 people become ill from norovirus infections each year. Almost 15,000 of these people are hospitalized, primarily due to dehydration, and 149 die.