Number of people sickened in E. coli outbreak linked to McDonald's rises to 90: CDC

The number of cases in the E. coli outbreak linked to McDonald's Quarter Pounders has risen to 90, federal health officials said in an update on Wednesday.

Cases have been reported in 13 states, according to the Centers for Disease Control and Prevention (CDC).

Most of the cases have been in Colorado, which has 29 reported cases, and Montana, which has 17 reported cases, according to the CDC.

Cases have also been reported in Iowa, Kansas, Michigan, Missouri, Nebraska, New Mexico, Oregon, Utah, Washington, Wisconsin and Wyoming, according to the CDC, which further notes that illnesses have occurred between Sept. 27 and Oct. 16 of this year.

At least 27 people have been hospitalized and two people developed hemolytic uremic syndrome (HUS), a serious condition that can cause kidney failure, according to the CDC.

One death has been reported in Colorado in connection with the outbreak. The person was a resident of Mesa County in the western part of the state, according to the Mesa County department of health. The patient who died is not one of the two who developed HUS.

The CDC said the number of cases could rise because it usually takes between three and four weeks to determine if an illness is linked to an outbreak. Additionally, the true number may be higher because many people recover without medical care and are not tested for E. coli, the CDC said.

Of the people interviewed by the CDC who fell ill, most reported eating the Quarter Pounder hamburger at McDonald's before becoming sick.

Epidemiologic and traceback data shows fresh, slivered onions used on the Quarter Pounder and other menu items are the likely source of the outbreak, according to the CDC.

McDonald's stopped using slivered onions on the Quarter Pounder hamburger in some states to try to prevent more people from getting sick.

Additionally, Taylor Farms, the supplier of slivered onions to the affected McDonald's locations, also recalled yellow onions, the CDC said.

All of the newly reported illnesses occurred before McDonald's and Taylor Farms took action to remove onions from McDonald's locations.

After stopping distribution of Quarter Pounder beef patties in affected areas last week, McDonald's is now asking their beef suppliers to produce a new supply of fresh patties to resume distribution.

The Quarter Pounder is expected to be available in all restaurants in the coming week, according to the company's update on Sunday.

The CDC recommends those who have severe E. coli symptoms -- including bloody diarrhea, a fever higher than 102 F and vomiting -- to contact a health care provider immediately.

ABC News' Youri Benadjaoud contributed to this report.