Investigation Details
Posted October 4, 2022
This outbreak is over. Learn what you can do to protect yourself from getting sick from E. coli.
CDC, public health and regulatory officials in several states, the U.S. Food and Drug Administration (FDA), and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) investigated a multistate outbreak of E. coli O157:H7 infections but were unable to confirm the food source.
Investigators could not confirm romaine lettuce as the source of this outbreak. This is partly because the Wendy’s meals eaten by sick people had many similar ingredients. Additionally, there were no laboratory or traceback data that could confirm romaine lettuce as the source.
As of October 4, 2022, this outbreak is over.
Epidemiologic Data
A total of 109 people infected with the outbreak strain of E. coli O157:H7 were reported from 6 states (see map). Illnesses started on dates ranging from July 26, 2022, to August 17, 2022 (see timeline).
Sick people ranged in age from 1 to 94 years, with a median age of 22 years, and 55% were male. Of 97 people with information available, 52 were hospitalized and 13 developed hemolytic uremic syndrome, a serious condition that can cause kidney failure. No deaths were reported.
The true number of sick people in this outbreak is likely much higher than the number reported, and the outbreak may not have been limited to the states with known illnesses. This is because many people recover without medical care and are not tested for E. coli.
State and local public health officials interviewed people about the foods they ate in the week before they got sick. Among 82 people with detailed food history, 68 (83%) reported eating at a Wendy’s restaurant in the week before their illness started. The Wendy’s restaurants where sick people ate were in Indiana, Kentucky, Michigan, New Jersey, Ohio, and Pennsylvania. People reported eating a variety of menu items, including burgers and sandwiches. Of 68 people with detailed information about what they ate at Wendy’s, 46 (68%) reported eating romaine lettuce served on burgers and sandwiches.
Laboratory and Traceback Data
Public health investigators used the PulseNet system to identify illnesses that were part of this outbreak. CDC PulseNet manages a national database of DNA fingerprints of bacteria that cause foodborne illnesses. DNA fingerprinting is performed on bacteria using a method called whole genome sequencing (WGS).
WGS showed that bacteria from sick people’s samples were closely related genetically. This suggests that people got sick from eating the same food.
Several food items were tested during the outbreak investigation, but the outbreak strain was not identified.
WGS analysis of bacteria from 108 people’s samples predicted resistance to chloramphenicol, streptomycin, sulfisoxazole, tetracycline, and trimethoprim-sulfamethoxazole; analysis of bacteria from one person’s sample did not predict resistance to any antibiotics. Standard antimicrobial resistance testing of clinical isolates by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory is currently underway. These findings do not affect treatment guidance since antibiotics are not recommended for people with E. coli O157:H7 infections.
Public Health Actions
On August 19, 2022, Wendy’s took the precautionary measure of removing the romaine lettuce being used in burgers and sandwiches at restaurants in states where sick people ate.
During the outbreak, CDC provided updates and advised people to call their healthcare provider right away if they had severe E. coli symptoms.
Investigators are continuing to collect different types of data to identify the food source of this multistate outbreak of E. coli O157:H7 infections. A specific food has not yet been confirmed as the source of this outbreak, but many sick people reported eating burgers and sandwiches with romaine lettuce at Wendy’s restaurants before getting sick.
Epidemiologic Data
Since the last update on August 25, 2022, 13 more illnesses have been reported to CDC. As of August 31, 2022, a total of 97 people infected with the outbreak strain of E. coli O157:H7 have been reported from six states (see map). Illnesses started on dates ranging from July 26, 2022, to August 15, 2022 (see timeline).
Sick people range in age from 3 to 94 years, with a median age of 22 years, and 55% are male. Of 81 people with information available, 43 have been hospitalized and 10 developed hemolytic uremic syndrome, a serious condition that can cause kidney failure. No deaths have been reported.
The true number of sick people in this outbreak is likely higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because some of the recent illnesses have not yet been reported to PulseNet as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak. In addition, some people recover without medical care and are not tested for E. coli.
State and local public health officials have been interviewing people about the foods they ate in the week before they got sick. Among 67 people with detailed food history, 54 (81%) reported eating at a Wendy’s restaurant in the week before their illness started. The Wendy’s restaurants where sick people ate are in Indiana, Michigan, Ohio, and Pennsylvania. People reported eating a variety of menu items, including burgers and sandwiches. Of 54 people with detailed information about what they ate at Wendy’s, 37 (69%) reported eating romaine lettuce served on burgers and sandwiches. Investigators continue to analyze data at the ingredient level to determine if there are any other possible foods that could be the source of the outbreak.
Investigators are continuing to collect different types of data to identify the food source of this multistate outbreak of E. coli O157:H7 infections. A specific food has not yet been confirmed as the source of this outbreak, but many sick people reported eating burgers and sandwiches with romaine lettuce at Wendy’s restaurants before getting sick.
Epidemiologic Data
Since the last update on August 19, 2022, 47 more illnesses have been reported to CDC. As of August 24, 2022, a total of 84 people infected with the outbreak strain of E. coli O157:H7 have been reported from 4 states (see map). Illnesses started on dates ranging from July 26, 2022, to August 9, 2022 (see timeline).
Sick people range in age from 5 to 94 years, with a median age of 24 years, and 52% are male. Of 73 people with information available, 38 have been hospitalized and 8 people in Michigan have developed a type of kidney failure called hemolytic uremic syndrome. No deaths have been reported.
The true number of sick people in this outbreak is likely higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because some of the recent illnesses have not yet been reported to PulseNet as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak. In addition, some people recover without medical care and are not tested for E. coli.
State and local public health officials have been interviewing people about the foods they ate in the week before they got sick. Among 62 people who have been interviewed, 52 (84%) reported eating at a Wendy’s restaurant in the week before their illness started. The Wendy’s restaurants where sick people ate are in Indiana, Michigan, Ohio, and Pennsylvania. People reported eating a variety of menu items, including burgers and sandwiches. Of 17 people with detailed information about what they ate at Wendy’s, 15 (88%) reported eating romaine lettuce served on burgers and sandwiches. Investigators continue to analyze data at the ingredient level to determine if there are any other possible foods that could be the source of the outbreak.
CDC, public health and regulatory officials in several states, the U.S. Food and Drug Administration (FDA), and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) are collecting different types of data to identify the food source of this multistate outbreak of E. coli O157:H7 infections. A specific food has not yet been confirmed as the source of this outbreak, but many sick people reported eating burgers and sandwiches with romaine lettuce at Wendy’s restaurants before getting sick.
Epidemiologic Data
Since the last update on August 17, 2022, eight more illnesses have been reported and two new states have reported illnesses. As of August 18, 2022, a total of 37 people infected with the outbreak strain of E. coli O157:H7 have been reported to CDC from 4 states (see map). Illnesses started on dates ranging from July 26, 2022, to August 8, 2022 (see timeline).
Sick people range in age from 6 to 91 years, with a median age of 21 years, and 62% are male. Of 24 people with information available, ten have been hospitalized. Among the ten people who have been hospitalized, three people in Michigan have developed a type of kidney failure called hemolytic uremic syndrome. No deaths have been reported.
The true number of sick people in this outbreak is likely higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because some of the recent illnesses have not yet been reported to PulseNet as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak. In addition, some people recover without medical care and are not tested for E. coli.
State and local public health officials have been interviewing people about the foods they ate in the week before they got sick. Among 26 people who have been interviewed, 22 (86%) reported eating at a Wendy’s restaurant in the week before their illness started. The Wendy’s restaurants where sick people ate are in Michigan, Ohio, and Pennsylvania. People reported eating a variety of menu items, including burgers and sandwiches. Romaine lettuce served on burgers and sandwiches at Wendy’s was one of the most common ingredients eaten among the menu items, but investigators continue to analyze data at the ingredient level to determine if there are any other possible foods that could be the source of the outbreak.
Public Health Actions
Based on the information available, Wendy’s is taking the precautionary measure of removing the romaine lettuce being used in sandwiches from restaurants in that region. Wendy’s uses a different type of romaine lettuce for salads. Investigators are working to confirm whether romaine lettuce is the source of this outbreak, and whether romaine lettuce used in Wendy’s sandwiches was served or sold at other businesses. Wendy’s is fully cooperating with the investigation.
CDC, public health and regulatory officials in several states, the U.S. Food and Drug Administration (FDA), and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) are collecting different types of data to identify the food source of a multistate outbreak of E. coli O157:H7 infections. So far, illnesses have only been reported from Michigan and Ohio. A food has not yet been identified as the source and this investigation is ongoing.
Epidemiologic and Laboratory Data
Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. CDC PulseNet manages a national database of DNA fingerprints of bacteria that cause foodborne illnesses. DNA fingerprinting is performed on bacteria using a method called whole genome sequencing (WGS).
Michigan and Ohio have both reported large increases in the number of E. coli infections in their states. Some of these illnesses have not yet been reported to the PulseNet system, but investigators are working quickly to add them to PulseNet to determine if they may be part of this outbreak. WGS from the illnesses in PulseNet showed that bacteria from sick people’s samples are closely related genetically. This suggests that people in this outbreak got sick from the same food.
As of August 16, 2022, a total of 29 people infected with the outbreak strain of E. coli O157:H7 have been reported to CDC from 2 states (see map). Illnesses started on dates ranging from July 26, 2022, to August 6, 2022 (see timeline).
Sick people range in age from 6 to 91 years, with a median age of 21 years, and 38% are female. Of 17 people with information available, 9 have been hospitalized. No deaths have been reported.
As mentioned above, the true number of sick people in an outbreak is likely higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because some of the recent illnesses have not yet be reported to PulseNet as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak. In addition, some people recover without medical care and are not tested for E. coli. State and local public health officials are interviewing people about the foods they ate in the week before they got sick.
Public Health Actions
Investigators are working quickly to identify the source of these infections. If a food item is identified, investigators will issue advice for people and businesses. People who are sick with E. coli symptoms should report their illnesses to their local or state health department. In general, to prevent getting sick from E. coli, follow these four steps when handling or preparing food: clean, separate, cook, and chill.
