The agency said that no food had been identified yet as the source of the outbreak, which has sickened 14 people in Ohio and 15 in Michigan.Federal health officials said Wednesday that they were investigating an E. coli outbreak that has been linked to a growing number of illnesses in Ohio and Michigan.The Centers for Disease Control and Prevention said that no food had been identified yet as the source of the “fast-moving” outbreak, which has sickened 14 people in Ohio and 15 in Michigan. Nine people have been hospitalized. No deaths have been reported.The Michigan Department of Health and Human Services said on Tuesday that it had received reports of 98 cases of E. coli infections in August, compared with 20 cases during the same period last year. The investigation is in the early stages, the department said, and laboratory results have linked some of the cases to one another.“While reports of E. coli illness typically increase during the warmer summer months, this significant jump in cases is alarming,” Dr. Natasha Bagdasarian, Michigan’s chief medical executive, said in a statement.“This is a reminder to make sure to follow best practices when it comes to hand hygiene and food handling to prevent these kinds of food-borne illness,” she said.Anyone who experiences E. coli symptoms such as cramping, diarrhea or gastrointestinal distress should contact their health care provider, especially if such symptoms are severe, Dr. Bagdasarian said.Other common symptoms include vomiting and fever. Symptoms usually start three to four days after swallowing E. coli bacteria, and most people recover without treatment within five to seven days, according to the C.D.C.Some people may develop a type of kidney failure and require hospitalization, the C.D.C. said. The current outbreak has affected people from 6 to 91 years old.The Ohio Department of Health said that cases had been reported in Wood, Lucas, Mahoning, Clermont, Cuyahoga, Franklin, Lorain and Summit counties. Four people in Ohio have been hospitalized in connection with the outbreak, the department said.The C.D.C. urged people to prevent infection by washing their hands as well as their utensils and cooking surfaces, rinsing fruits and vegetables under running water, keeping raw meat, poultry and seafood away from other foods and cooking meat to a temperature high enough to kill germs.Heath officials also advise people to thaw foods in the refrigerator instead of on the counter. Other recommendations include not swallowing water in lakes, ponds, streams, swimming pools and backyard “kiddie” pools.E. coli is commonly found in the intestines, and infections can begin when someone ingests food contaminated with feces, according to the C.D.C.In 2019, an E. coli outbreak linked to romaine lettuce infected 167 people in 27 states, according to the C.D.C. No deaths were reported but 85 people were hospitalized, including 15 people who had kidney failure.Lab testing and data analysis showed the outbreak was caused by the same strain of E. coli that led to outbreaks linked to leafy greens in 2017 and to romaine lettuce in 2018.E. coli outbreaks last year were linked to packaged salads, baby spinach, cake mix and an unknown food source, according to the C.D.C.