Deputy chief medical health officer Denis Allard says investigators have been unable to identify any common sources among the four patients in Fredericton.
Two patients who were seriously ill were recently released from the hospital.
It's the second outbreak of E. coli in New Brunswick in the last two months.
In June, health officials determined that romaine lettuce consumed at a Jungle Jim's restaurant in Miramichi was the likely source of an outbreak of the same E. coli strain.
There were 13 confirmed cases, although no one developed serious complications.
Both strains were the same one found during the Walkerton, Ont., water disaster in 2000 that killed seven people.