They range in age from 2 to 73-years-old and 75% of them are children under 18, the CDC said.
Seven people had to be hospitalized, the CDC said, including one who developed hemolytic uremic syndrome, a type of kidney failure. No deaths have been reported.
All of the sick people are women, the CDC said.
Six of the eight people who had been interviewed by state and local health officials, at last report, said they had eaten or tasted cake batter made from a cake mix, the CDC said.
"People reported buying different varieties and brands of cake mix," the notice said.
The Food and Drug Administration is looking at purchase records from the locations where sick people bought cake mix to try to find a common brand or production facility, the CDC said.
Investigators performed DNA fingerprinting on the bacteria in the sick people's samples and found that they were closely related genetically.
"This means that people in this outbreak likely got sick from the same food," the CDC said.
The number of people sickened is likely much higher, the notice said, because many people recover without medical treatment and are never tested for E. coli.
It also takes three to four weeks to determine if a sick person is part of an outbreak, the CDC said.