Investigation Details

Posted February 2, 2021

February 2, 2021

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.

Epidemiologic Data

As of February 1, 2021, a total of 16 people infected with the outbreak strain have been reported from 5 states. This map shows where sick people live.

Illnesses started on dates ranging from December 23, 2020, to January 7, 2021. This chart shows when people got sick. Recent illnesses may not yet be reported as it usually takes 2 to 4 weeks to link illnesses to an outbreak.

Sick people range in age from 10 to 95 years, with a median age of 31, and 88% are female. Of 12 people with information available, 9 have been hospitalized. Of 11 people with information, 3 developed a type of kidney failure called hemolytic uremic syndrome (HUS). One death has been reported from Washington.

State and local public health officials are interviewing people to find out what foods they ate in the week before they got sick.

Laboratory and Traceback 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).

WGS showed that bacteria from sick people’s samples are closely related genetically. This means that people in this outbreak likely got sick from eating the same food.

WGS also showed that this outbreak strain has been previously linked to various sources, including romaine lettuce and recreational water. More information is needed to identify the source of this outbreak.

Previous Updates

Since the last update on March 27, no additional illnesses have been reported.

As of April 8, 2020, 36 people infected with the outbreak strain of Listeria monocytogenes have been reported from 17 states. A list of the states and the number of cases in each can be found on the Map of Reported Cases page.

Listeria was identified in ill people’s samples from November 23, 2016, to December 13, 2019. Ill people range in age from less than 1 to 97 years, with a median age of 67. Fifty-eight percent of ill people are female. Of 32 ill people with information available, 30 hospitalizations have been reported. Four deaths have been reported from California, Hawaii, and New Jersey. Six cases are pregnancy-associated and two resulted in fetal loss.

Investigation of the Outbreak

Epidemiologic, traceback, and laboratory evidence indicates that enoki mushrooms labeled as “Product of Korea” are the likely source of this outbreak.

State and local public health officials interviewed ill people about the foods they ate in the month before they became ill. Twelve out of 22 (55%) reported eating mushrooms, including enoki, portobello, white, button, cremini, wood ear, maitake, and oyster.

FDA collected samples of enoki mushrooms at import from Green Co. of the Republic of Korea for testing. On April 6, testing results showed that two samples yielded the outbreak strain of Listeria monocytogenes. As a result, on April 7, Green Co. was placed on Import Alert 99-23external icon and H&C Foods Inc. recalled enoki mushrooms supplied by Green Co.

On March 10, the California Department of Public Health collected enoki mushrooms for testing from grocery stores. Testing identified Listeria monocytogenes in one sample, and whole genome sequencing is being conducted to determine if the Listeria in these recalled mushrooms is the same as the outbreak strain. These mushrooms are labeled as “Product of Korea” and were distributed by Guan’s Mushroom Co. On March 23, Guan’s Mushroom Co. recalled its enoki mushrooms.

On February 25, the Michigan Department of Agriculture and Rural Development collected mushrooms for testing from a grocery store where an ill person purchased enoki mushrooms. Two samples of enoki mushrooms yielded the outbreak strain of Listeria monocytogenes. These mushrooms are labeled as “Product of Korea” and were distributed by Sun Hong Foods, Inc. On March 9, Sun Hong Foods, Inc. recalled its enoki mushrooms.

Consumers, food service operators, and retailers should not eat, serve, or sell recalled enoki mushrooms.

On March 18, the Korean Ministry of Food and Drug Safety issued a press release about their investigation findings. They detected Listeria monocytogenes in enoki mushrooms produced by two firms in Korea.

CDC is concerned that enoki mushrooms from Korea (Republic of Korea) may be contaminated with Listeria monocytogenes. We are advising people who are more likely to develop a Listeria infection – pregnant women, adults age 65 or older, and people with weakened immune systems – to avoid eating any enoki mushrooms from Korea, until investigators determine the source of contamination and if additional products are linked to illness.

CDC will provide updates when more information is available.

Since the last update on March 27, no additional illnesses have been reported.

As of April 8, 2020, 36 people infected with the outbreak strain of Listeria monocytogenes have been reported from 17 states. A list of the states and the number of cases in each can be found on the Map of Reported Cases page.

Listeria was identified in ill people’s samples from November 23, 2016, to December 13, 2019. Ill people range in age from less than 1 to 97 years, with a median age of 67. Fifty-eight percent of ill people are female. Of 32 ill people with information available, 30 hospitalizations have been reported. Four deaths have been reported from California, Hawaii, and New Jersey. Six cases are pregnancy-associated and two resulted in fetal loss.

Investigation of the Outbreak

Epidemiologic, traceback, and laboratory evidence indicates that enoki mushrooms labeled as “Product of Korea” are the likely source of this outbreak.

State and local public health officials interviewed ill people about the foods they ate in the month before they became ill. Twelve out of 22 (55%) reported eating mushrooms, including enoki, portobello, white, button, cremini, wood ear, maitake, and oyster.

FDA collected samples of enoki mushrooms at import from Green Co. of the Republic of Korea for testing. On April 6, testing results showed that two samples yielded the outbreak strain of Listeria monocytogenes. As a result, on April 7, Green Co. was placed on Import Alert 99-23external icon and H&C Foods Inc. recalled enoki mushrooms supplied by Green Co.

On March 10, the California Department of Public Health collected enoki mushrooms for testing from grocery stores. Testing identified Listeria monocytogenes in one sample, and whole genome sequencing is being conducted to determine if the Listeria in these recalled mushrooms is the same as the outbreak strain. These mushrooms are labeled as “Product of Korea” and were distributed by Guan’s Mushroom Co. On March 23, Guan’s Mushroom Co. recalled its enoki mushrooms.

On February 25, the Michigan Department of Agriculture and Rural Development collected mushrooms for testing from a grocery store where an ill person purchased enoki mushrooms. Two samples of enoki mushrooms yielded the outbreak strain of Listeria monocytogenes. These mushrooms are labeled as “Product of Korea” and were distributed by Sun Hong Foods, Inc. On March 9, Sun Hong Foods, Inc. recalled its enoki mushrooms.

Consumers, food service operators, and retailers should not eat, serve, or sell recalled enoki mushrooms.

On March 18, the Korean Ministry of Food and Drug Safety issued a press release about their investigation findings. They detected Listeria monocytogenes in enoki mushrooms produced by two firms in Korea.

CDC is concerned that enoki mushrooms from Korea (Republic of Korea) may be contaminated with Listeria monocytogenes. We are advising people who are more likely to develop a Listeria infection – pregnant women, adults age 65 or older, and people with weakened immune systems – to avoid eating any enoki mushrooms from Korea, until investigators determine the source of contamination and if additional products are linked to illness.

CDC will provide updates when more information is available.