An outbreak of E.Coli linked to McDonald’s Quarter Pounders has sickened at least 49 people in 10 states and has been linked to one death, federal officials said.

McDonald’s supplier Taylor Farms has recalled yellow onions produced in its Colorado plant out of what it said was an “abundance of caution” related to the outbreak. The California-based food supplier is being investigated by the Food and Drug Administration as a “likely source of contamination,” CNBC reported.

Several other fast food restaurants, including Taco Bell, Pizza Hut, KFC and Burger King, have removed onions from some menus.

Colorado (26) and Nebraska (9) have reported the most cases but there have also been reports in Oregon, Montana, Wyoming, Utah, Kansas, Missouri, Iowa and Wisconsin. The death was of an “older” person in Colorado, according to the CDC, and one child was hospitalized with complications of hemolytic uremic syndrome, a serious complication that can result from E.coli infection.

All of the patients reported eating at McDonald’s before their illness started and most specifically mentioned eating a Quarter Pounder hamburger, the CDC said.

There are likely more cases than have been reported, the CDC advised, and people were asked to seek medical attention if they show symptoms of E.coli.

READ MORE: McDonald’s Quarter Pounders linked to multi-state E coli outbreak, 1 death, CDC alert warns

What are symptoms of E. coli infection?

Most E. coli are harmless and part of a healthy intestinal tract that can help digest food, protect vitamins and protect from other germs. But some E. coli can make people sick which happens after people ingest contaminated food or water or come into contact with feces of animals or infected people.

Most people infected with Shiga toxin-producing E. coli experience severe stomach cramps, diarrhea that’s often bloody and vomiting. Many patients also experience low-grade fever. One of the dangers of E. coli infection is the risk of dehydration. Symptoms of dehydration include lack of urination, dry mouth and throat and dizziness.

Symptoms usually start within three to four days after swallowing the bacteria and most people recover on their own within a week. Some people however, particularly the young or old or those with other health issues, may need to be hospitalized.