Seven people in three states became ill in an outbreak of E. coli O157:H7 linked to unshelled hazelnuts sold during the holiday season.

The outbreak, in Michigan, Minnesota and Wisconsin, prompted the Los Angeles-based distributor, DeFranco and Sons, to recall bulk and packaged unshelled hazelnuts, as well as mixed nut products containing hazelnuts (which are also called filberts).

The nuts, sold under the brand names Sunripe and George Packing, were distributed to retailers from Nov. 2 through Dec. 22, 2010.  Minnesota health authorities said the unshelled hazelnuts were shipped to stores in Minnesota, Iowa, Michigan, Montana, North Dakota, South Dakota and Wisconsin. DeFranco, however, said they may have been shipped nationwide and to Canada. Because they have a long shelf life, the nuts may still be in consumers’ homes.

So far, lab samples have not confirmed E. coli O157:H7 in the nuts. The investigation will likely focus on farms in Oregon, where virtually all of the nation’s hazelnuts are grown, but determining the source of contamination may not be possible.

Health departments in Minnesota, Michigan and Wisconsin said they were alerted to seven E. coli cases with the same DNA fingerprint and illness onsets between Dec. 20 and Jan. 28. All the case patients reported eating hazelnuts.

Three of those infected are residents of Minnesota, three live in Wisconsin and one is from Michigan.

Six of the case patients told health investigators the nuts had come from bulk bins in grocery stores and one said the nuts had been packaged. Four said the hazelnuts were part of a mixed-nut assortment.

The Wisconsin Department of Health Services, in its news release, said one of its case patients was a child. None of the three Wisconsin residents was hospitalized, but the health department said there were hospitalizations in the other states.

State and federal officials said the hazelnuts included in the recall should not be eaten. To help identify whether hazelnuts are part of the recall, the MDA website at lists stores that sold the bulk nuts.

The U.S. Food and Drug Administration news release also has information about the recalled brands–Sunripe in-shell hazelnuts and hazelnuts with mixed nuts, in 1 to 50 lb. bags, most with sell by dates of June 30, 2011 and George Packing hazelnuts in 50 lb. lots.

Shelled hazelnuts and products containing hazelnuts as an ingredient have not been linked to any illnesses and are not part of the recall. 

Consumers who think they may have the affected hazelnuts, or mixed nut products containing hazelnuts, should check with the store where they were purchased to determine if they are subject to the recall. Consumers with questions can contact the company at 800-993-3992, Monday through Friday, from 2 to 4 p.m. Pacific time.

Hazelnuts have been recalled before but not associated with an outbreak. In 2009, the FDA detected Salmonella in a processing plant in Newberg, Oregon, which led to a recall of more than 114,000 of shelled hazelnuts. No illnesses were reported in that recall.