Public health officials are investigating a growing number of illnesses linked to E. coli bacteria in Michigan and Ohio, the Centers for Disease Control and Prevention said this week. At least 29 cases have been reported so far, and CDC says the number is expected to increase.

The CDC says it has not yet identified the food that is causing the “fast-moving outbreak.” It urged anyone with symptoms of an E. coli infection to report them to their local health departments. Fever, diarrhea, vomiting, dizziness, and dehydration are some signs of the infection.

The onset of symptoms typically happens three or four days after a person ingests the bacteria, and most people who get sick will recover without treatment within seven days, the CDC said. 

Of the 29 cases so far linked to the current E. coli outbreak — 15 in Michigan and 14 in Ohio — nine people required hospitalization. No deaths have been reported.

The Michigan Department of Health and Human Services issued its own announcement about rising E. coli illnesses in the state, and said it has partnered with local health departments in Kent, Ottawa and Oakland counties to investigate the cause. 

Nearly 100 cases were reported to the state health department since the beginning of August, according to the announcement, which is roughly five times the number of cases reported over the same time period last year. Lab testing indicates some of the current cases are related to one another, the health department said. However, it emphasized that the investigation underway in Michigan is still “in the early stages.”

“While reports of E. coli illness typically increase during the warmer summer months, this significant jump in cases is alarming,” Dr. Natasha Bagdasarian, the chief medical executive at Michigan’s health department, 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 foodborne illness.”

A spokesperson at the Ohio Department of Health said cases reported in the state have come from Clermont, Cuyahoga, Franklin, Wood, Lorain, Lucas, Mahoning and Summit counties, according to CBS affiliate WBNS, adding that four of the nine cases requiring hospitalization are in Ohio.

Like health officials in Michigan and Ohio, the CDC is encouraging people to take extra precautions when handling food to reduce their risks of consuming or spreading E. coli. Washing hands, utensils and surfaces that may come into contact with food; washing produce; separating raw foods from cooked ones; and refrigerating anything perishable is recommended. Health officials also recommend using a thermometer to make sure foods are cooked at a temperature high enough to kill the germ.

One of the most recent major E. coli outbreaks happened toward the end of 2019, when almost 200 people across more than half of U.S. states became ill after eating contaminated romaine lettuce. Months after giving the public the green light to consume the lettuce again, regulators at the Food and Drug Administration said cow feces, as a result of “the proximity of cattle to produce fields” likely contributed to the contamination.