2015 Salmonella Outbreak Linked to Frozen Raw Tuna

Final Case Count Update

Since the last update on July 22, 2015, two additional ill people were reported. One person was reported from California and was infected with Salmonella Paratyphi B variant L(+) tartrate(+) and the other person was reported from Arizona and was infected with Salmonella Weltevreden.

A total of 65 people infected with one of the outbreak strains of Salmonella Paratyphi B variant L(+) tartrate(+) (64 people) or Salmonella Weltevreden (1 person) were reported from 11 states. The number of ill people reported from each state was as follows: Arizona (12), California (35), Illinois (1), Michigan (2), Minnesota (4), Mississippi (1), New Mexico (6), South Dakota (1), Virginia (1), Washington (1), and Wisconsin (1).

Illness onset dates ranged from March 5, 2015 to July 20, 2015. Ill people ranged in age from younger than 1 year to 83 with a median age of 31, and 54% were male. Among 62 people with available information, 11 (18%) were hospitalized, and no deaths were reported.

Case Count Update

Since the last update on July 15, 2015, two new ill people infected with the outbreak strain of Salmonella Paratyphi B variant L(+) tartrate(+) have been reported from Minnesota. As of July 20, 2015, 62 people have been reported from 11 states. The number of ill people reported from each state is as follows: Arizona (11), California (34), Illinois (1), Michigan (1), Minnesota (4), Mississippi (1), New Mexico (6), South Dakota (1), Virginia (1), Washington (1), and Wisconsin (1).

Illness onset dates range from March 5, 2015 to July 7, 2015. Ill people range in age from younger than 1 year to 83 with a median age of 32, and 56% are male. Among 59 people with available information, 11 (19%) have been hospitalized, and no deaths have been reported.

Illnesses that occurred after June 19, 2015 might not yet be reported due to the time between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Investigation Update

On July 21, 2015, Osamu Corporation announced two voluntary recalls of frozen yellowfin tuna from one processing plant in Indonesia. Osamu recalled all frozen yellowfin tuna (loin, saku, chunk, slice, and ground market forms) sold to restaurants and grocery stores throughout the U.S. from May 9, 2014 to July 9, 2015. Affected products can be identified by four-digit purchase order numbers 8563 through 8599 located on each product carton box. Additionally, Osamu recalled one lot of frozen yellowfin tuna chunk meat distributed to AFC Corporation from May 20, 2015 to May 26, 2015 after the Minnesota Department of Health and Department of Agriculture isolated the outbreak strain from samples of unopened frozen raw tuna collected from a Minnesota grocery store where an ill person in this outbreak reported eating tuna sushi. The affected lot can be identified by lot number 68568.

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill people and to interview them about foods they ate before they became ill. CDC will provide updates when more information is available.

Case Count Update

Since the last update on June 5, 2015, seven new ill people infected with the outbreak strain of Salmonella Paratyphi B variant L(+) tartrate(+) have been reported from Arizona (1), California (3), Michigan (1), and Minnesota (2). As of July 14, 2015, 60 people have been reported from 11 states. The number of ill people reported from each state is as follows: Arizona (11), California (34), Illinois (1), Michigan (1), Minnesota (2), Mississippi (1), New Mexico (6), South Dakota (1), Virginia (1), Washington (1), and Wisconsin (1).

Illness onset dates range from March 5, 2015 to June 30, 2015. Ill people range in age from younger than 1 year to 83 with a median age of 32, and 56% are male. Among 57 people with available information, 11 (19%) have been hospitalized, and no deaths have been reported.

Illnesses that occurred after June 13, 2015 might not yet be reported due to the time between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Investigation Update

Epidemiologic and laboratory findings indicate that frozen raw tuna is the likely source of the infections. In interviews, ill people answered questions about foods eaten and other exposures in the week before they became ill. Of 46 ill people for whom information is known, 43 (93%) reported consuming sushi in the week before they became ill. This proportion is significantly higher when compared with results from a survey [PDF – 29 pages] of healthy people in which 5% reported eating “sushi, sashimi, or ceviche made with raw fish or shellfish” in the 7 days before they were interviewed. Of the 42 people with information about their sushi exposure, 41 (98%) reported eating a sushi item containing raw tuna, and 25 (86%) of 29 with information reported eating a sushi item containing raw “spicy tuna.” The traceback investigation is ongoing, but preliminary investigation identified that frozen raw tuna was used to make the raw tuna sushi reported by ill persons.

The Minnesota Department of Health and Department of Agriculture isolated the outbreak strain from samples of unopened frozen raw tuna products collected from a Minnesota grocery store where an ill person in this outbreak reported eating tuna sushi. The contaminated frozen raw tuna products collected from the store represented one lot of product imported from Indonesia by Osamu Corporation.

The National Antimicrobial Resistance Monitoring System (NARMS) is a U.S. public health surveillance system that tracks antibiotic resistance in foodborne and other enteric bacteria found in people, raw meat and poultry, and food-producing animals. NARMS is a partnership among the CDC, the U.S. Food and Drug Administration (FDA), the U.S. Department of Agriculture (USDA), and state and local health departments.

The NARMS human surveillance program at CDC monitors antibiotic resistance in Salmonella and other bacteria isolated from clinical specimens submitted to NARMS by public health laboratories. CDC’s NARMS laboratory conducted antibiotic resistance testing on clinical isolates collected from three ill people infected with the outbreak strain. Of the three isolates, one (33%) isolate was resistant to ampicillin and two (67%) were susceptible to all antibiotics tested on the NARMS panel.

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill people and to interview them about foods they ate before they became ill. CDC will provide updates when more information is available.

Case Count Update

As of June 4, 2015, no new ill people infected with the outbreak strain of Salmonella Paratyphi B variant L(+) tartrate(+) have been identified. CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill people and to interview them about foods they ate before they became ill.

Investigation Update

As a result of the ongoing investigation, the Maricopa County Environmental Services Department working with the Arizona State Public Health Laboratory tested unopened frozen ground tuna products. Arizona identified Salmonella Newport in one sample and Salmonella Weltevreden in another sample. The unopened frozen ground tuna products represented two different lots of product imported from Indonesia by Osamu Corporation of Gardena, California. On May 27, Osamu Corporation recalled [PDF – 1 page] the two lots of ground frozen yellowfin tuna imported from Indonesia due to possible Salmonella contamination.

A search of the PulseNet database did not identify any known human illnesses linked to the recall. State health departments continue to test samples of raw tuna products but the strain of Salmonella Paratyphi B variant L(+) tartrate(+) linked to the outbreak has not been identified.

FDA reports it has increased its monitoring of tuna. Additionally, FDA is conducting a traceback investigation. FDA is evaluating and analyzing records to determine whether there is a common source of raw tuna linked to the outbreak.

May 21, 2015

CDC is collaborating with public health officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Salmonella Paratyphi B variant L(+) tartrate(+) infections. The investigation has not conclusively identified the source of this outbreak, but most ill people interviewed reported eating sushi made with raw tuna in the week before becoming ill. The investigation is ongoing and has not identified a common brand or supplier of raw tuna linked to illnesses.

This outbreak is caused by Salmonella Paratyphi B variant L(+) tartrate(+) bacteria. The illness caused by this bacteria typically includes diarrhea, fever, and abdominal cramps 12-72 hours after being exposed. Salmonella Paratyphi B variant L(+) tartrate(+) does not cause paratyphoid fever, enteric fever, or typhoid fever.

Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA “fingerprinting” is performed on Salmonella bacteria isolated from ill people by using a technique called pulsed-field gel electrophoresis, or PFGE. PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks. This PFGE pattern has never been seen before in the PulseNet database.

As of May 21, 2015, a total of 53 people infected with the outbreak strain of Salmonella Paratyphi B variant L(+) tartrate(+) have been reported from 9 states. Most of the ill people have been reported from the southwestern United States, or reported travel to this part of the country in the week before they became ill. The number of ill people reported from each state is as follows: Arizona (10), California (31), Illinois (1), Mississippi (1), New Mexico (6), South Dakota (1), Virginia (1), Washington (1), and Wisconsin (1).

Illness onset dates range from March 5, 2015 to May 3, 2015. Ill people range in age from younger than 1 to 83 with a median age of 31, and 47% are female. Among 46 people with available information, 10 (22%) have been hospitalized, and no deaths have been reported.

This outbreak can be illustrated with a chart showing the number of people who became ill each day. This chart is called an epidemic curve or epi curve. Illnesses that occurred after April 21, 2015 might not yet be reported due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks. Please see the Timeline for Reporting Cases of Salmonella Infection for more details.

Investigation of the Outbreak

In interviews, ill people answered questions about foods eaten and other exposures in the week before they became ill. Interviews conducted to date suggest consumption of sushi made with raw tuna as a possible source of the infections. Of 37 ill people for whom information is known, 36 (97%) reported consuming sushi in the week before they became ill. This proportion is significantly higher when compared with results from a survey [PDF – 29 pages] of healthy people in which 5% reported eating “sushi, sashimi, or ceviche made with raw fish or shellfish” in the 7 days before they were interviewed. Of the 36 people reporting eating sushi, 34 (94%) reported eating a sushi item containing raw tuna, and 21 (81%) of 26 with information reported eating a sushi item containing raw “spicy tuna.”

Investigating clusters of illnesses can provide critical clues about the source of an outbreak. In this investigation, state and local officials have identified five clusters where ill people ate sushi at the same establishments. A cluster of illnesses is defined as more than one unrelated ill person (i.e., they do not know or live with each other) who report eating at the same restaurant location, attending a common event, or shopping at the same location of a grocery store before becoming ill. If several unrelated ill people ate or shopped at the same location of a restaurant or store within several days of each other, it suggests that the contaminated food item was served or sold there. Also, records kept at these locations may make it easier to trace suspected food items to identify a common point of contamination. State and local officials, along with FDA, are investigating these clusters to help identify a common brand or supplier of raw tuna possibly linked to this outbreak.

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill people and to interview them about foods they ate before they became ill. This investigation is evolving. CDC will provide updates when more information is available.