At least 75 people have gotten sick after eating McDonald’s Quarter Pounders linked to a deadly E. coli strain,the Centers for Disease Control and Prevention reported Friday.

The 75 cases, up from 49 on Tuesday, have been reported in 13 states. Twenty-two people, up from 10, have been hospitalized. The CDC said Tuesday that one person had died and reported no new deaths Friday.

The increase in people getting sick, which consists of older cases, was expected, as it can take several weeks for investigators to link illnessesto a food poisoning outbreak.The most recent case was Oct. 10.

“I think there will most certainly be more illnesses reported,” said Matt Wise, chief of the CDC’s Outbreak Response and Prevention Branch.

Public health officials have interviewed 42 people who became ill. All said they’d eaten at a McDonald’s before they got sick. Most, the CDC said in a statement, “specifically mentioned eating a Quarter Pounder hamburger.”

The people who’ve gotten sick have ranged in age from 13 to 88. Most are men. Two people, one teenager and one adult, have been hospitalized with a severe kidney condition called hemolytic uremic syndrome, which can lead to permanent kidney failure or even death, according to the CDC.

The number of cases is likely much higher than what’s been reported, as most people with E. coli infections recover on their own and are never tested for the bacteria.

E. coli symptoms — which include vomiting, diarrhea and a fever of at least 102 degrees — generally start three to four days after eating contaminated food.

The Food and Drug Administration and the CDC have zeroed in on the slivered onions served on the hamburgers as the likely source of contamination,although health officials haven’t ruled out the beef patties used for the Quarter Pounders.

On Thursday, McDonald’s confirmed that Taylor Farms, a California-based food producer, supplied the onions used on the contaminated Quarter Pounders.

Taylor Farms on Wednesday issued a recall on four raw onion products because of “potential E. Coli contamination.” Several restaurant chains in Colorado — including Taco Bell, Burger King, KFC, Pizza Hut and Illegal Pete’s — said they had removed onions from their menu following the recall out of an abundance of caution.

The FDA said restaurant chains who received the recalled onions have been directly notified. There are no signs of any illnesses linked to those restaurants, the CDC said.

“At this point, we are just not seeing anything reported in ill people that suggests there’s something going on outside of Quarter Pounders,” Wise said.

McDonald’s Quarter Pounders contain ingredients that aren’t found in other menu items: beef patties made specifically to be a quarter pound, as well as slivered onions. The chain’s classic hamburger and other sandwiches use rehydrated diced onions.

That’s why investigators have zeroed in on these specific ingredients.

McDonald’s has pulled the slivered onions and Quarter Pounder patties in question from its restaurants in at least 12 states: Colorado, Kansas, Utah, Wyoming, Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico and Oklahoma. Because those products have been removed, the CDC said the risk to the public is now low.

Late Friday, a McDonald’s spokesperson said the onions in question had been distributed to approximately 900 restaurants in Colorado, Kansas, Wyoming and “portions of other states” before they were pulled.

It remains unclear whether Taylor Farms transported the slivered onions directly to McDonald’s locations or if they arrived through a distributor. A spokesperson for McDonald’s said the restaurant chain gets its onion supply directly through Taylor Farms.

In a statement, Rachel Molatore, a spokesperson for Taylor Farms, said the company is working with the CDC and the FDA on the investigation into the source of the outbreak. The company’s products that are currently on the market are safe to eat, Molatore said.

McDonald’s is being sued by two people who said they fell ill after eating there.

The plaintiffs in the two lawsuits are both represented by Ron Simon, managing partner of Ron Simon & Associates, a food safety law firm. Simon told NBC News on Thursday that he’s representing a total of 15 people who say they were sickened in the outbreak.

CORRECTION (Oct. 25, 2024, 1:50): Because of an editing error, a previous version of this article misstated the number of previous hospitalizations. It was 10, not 20.