Next Steps for McDonald’s Following E. Coli Outbreak

As McDonald’s and health authorities race to contain a deadly E. coli outbreak, the burger chain faces challenges in the months ahead to keep the trust of diners and investors.

Shares of the fast-food giant have fallen 7% since the Centers for Disease Control and Prevention issued an advisory notice Tuesday, warning that the company’s Quarter Pounder burgers have been linked to an E. coli outbreak in 10 states that has led to one death.

Health investigators have zeroed in on the slivered onions used in the Quarter Pounder as the likely contaminant. McDonald’s confirmed that California-based vegetable producer Taylor Farms is the supplier of onions it removed from its supply chain. Taylor Farms issued a recall on four raw onion products, citing potential E. coli contamination, restaurant supplier U.S. Foods said in a notice to customers Thursday. (U.S. Foods is not a supplier for McDonald’s.)

The CDC initially reported 49 people became ill from the outbreak from Sept. 27 to Oct. 11. The tally has now risen to 75 cases across 13 states, including at least 22 hospitalizations, according to a CDC update on Friday. Health experts say the number of cases will likely rise as the investigation progresses.

Just two days after the CDC issued its advisory notice, it’s too soon to tell how the outbreak could affect McDonald’s business, especially if the case count grows. But investors are already worried that it could cause sales to fall at the company, which has been trying to rebound from lagging traffic by offering deals to price-sensitive customers.

Company spokespeople said Wednesday that’s it’s far too early to share if the outbreak was having any effect on its restaurants’ sales. McDonald’s is expected to report its third-quarter results on Oct. 29 before the markets open.

The damage to the business will depend in part on how effectively McDonald’s has already contained the outbreak — and how well it can convince diners it is safe to eat at its restaurants.

Investigations into multistate foodborne outbreaks can last from a few weeks to up to several months.

But Dr. Thomas Jaenisch, an epidemiology professor at the Colorado School of Public Health, believes it will likely take two or three weeks for federal agencies and McDonald’s to determine the exact source of contamination and chain of events leading to the E. coli outbreak. He said any testing of ingredients and supply sources “really shouldn’t take that long.”

The CDC has said the number of confirmed cases related to the McDonald’s E. coli outbreak could grow as the investigation continues, as many people recover from an infection without testing for it or receiving medical care. It also typically takes three to four weeks to determine if a sick patient is part of an outbreak, the agency added.

There’s also the possibility that cases could crop up in new states or regions that haven’t reported any illnesses, according to Xiang Yang, a professor and meat scientist at the University of California, Davis.

For example, a person traveling to a state impacted by the outbreak, such as Colorado, could have gotten infected with E. coli and brought it back to where they are from, according to Yang. It is also unclear if the onion supplier ships ingredients to restaurants in other regions of the U.S., which could potentially spread the E.coli strain that caused the McDonald’s outbreak.

That strain, called O157:H7, can cause a serious complication that can lead to kidney failure. One of the patients in the McDonald’s outbreak suffered from that condition, known as hemolytic uremic syndrome. The federal government essentially bans the sale of any ground beef contaminated with the strain, requiring suppliers to test their products for it.

E. coli can spread through contaminated food or water, or by an individual coming into contact with an infected person, environment or animal.

The CDC and the 10 states impacted have been interviewing each patient case to get detailed information about their exposure to E. coli, such as what they ate and when, according to Craig Hedberg, the co-director of the Minnesota Integrated Food Safety Center of Excellence. Hedberg is also a member of the McDonald’s Food Safety Advisory Council, but said he has not worked with the company on its response to the outbreak.

The CDC and the states have been sharing the information they gather with the Food and Drug Administration to trace onion distribution and identify a specific source of contamination, he said. The information is also shared with the U.S. Department of Agriculture’s Food Safety and Inspection Service, which does the same with ground beef.

The CDC is investigating both the Quarter Pounder’s uncooked slivered onions and its…