(Reuters) - The U.S. Centers for Disease Control and Prevention said on Wednesday that the number of infected people from the E.coli outbreak linked to McDonald's Quarter Pounder hamburgers has increased to 90 from 75.

The outbreak was first reported on Oct. 22 and on Wednesday, CDC said 27 persons have been hospitalized due to the illness, which has already killed one person.

Two of them developed hemolytic uremic syndrome (HUS), a serious condition that can cause kidney failure, as of Oct. 24.

The E. coli O157:H7 strain that led to the McDonald's outbreak is said to cause "very serious disease," especially for the elderly, children and people who are immunocompromised.

The U.S. Food and Drug Administration noted that symptoms begin anywhere from a few days after consuming contaminated food or up to nine days later.

As of Oct. 30, the outbreak has affected Colorado, Kansas, Utah, Wyoming, Iowa, Missouri, Montana, Nebraska, New Mexico, Oregon, Wisconsin, Washington and Michigan.

Colorado has reported the highest infections with 29 people who have fallen sick, while Montana reported 17 infections.

Initial findings by McDonald's and the FDA showed the outbreak was likely a result of the slivered onions used in the Quarter Pounder. The FDA and the company confirmed that Taylor Farms was the supplier for the affected locations.

Taylor Farms has recalled several batches of yellow onions produced in a Colorado facility, according to a recall memo on Wednesday by US Foods, one of the largest U.S. suppliers of food service operations.

The company along with the Colorado Department of Agriculture also ruled out the possibility of beef patties being a source of the outbreak.

McDonald's said that it would resume selling Quarter Pounders burgers this week after it temporarily took the item off the menu in a fifth of its 14,000 U.S. restaurants that were impacted.

On Tuesday, company executives brushed off any potential sales hit from the outbreak with CEO Chris Kempczinski apologizing to customers and adding that he was "confident in the safety of eating at McDonald's."