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Multistate Outbreak of Listeriosis Linked to Imported Frescolina Marte Brand Ricotta Salata Cheese (Final Update)

Posted November 21, 2012 2:30 PM ET

This outbreak appears to be over. Listeria monocytogenes infection (listeriosis) is an important cause of illness in the United States. More information about listeriosis, and steps people can take to reduce their risk of infection, can be found on the CDC Listeria Web Page.

At a Glance:

Highlights

Outbreak Summary  ⇑

Introduction

CDC collaborated with public health and regulatory officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Listeria monocytogenes infections (listeriosis). Joint investigation efforts indicated that ricotta salata cheese was the likely source.

Public health investigators used DNA “fingerprints” of Listeria obtained through diagnostic testing with pulsed-field gel electrophoresis, or PFGE, to identify cases of illness that were part of this outbreak. They used data from PulseNet, the national subtyping network made up of state and local public health laboratories and federal food regulatory laboratories that performs molecular surveillance of foodborne infections.

A total of 22 persons infected with the outbreak strain of Listeria monocytogenes were reported from 13 states and the District of Columbia. The number of ill people identified in each location was as follows: California (3), Colorado (1), District of Columbia (1), Maryland (3), Massachusetts (1), Minnesota (1), Nebraska (1), New Jersey (3), New Mexico (1), New York (1), Ohio (1), Pennsylvania (2), Virginia (2), and Washington (1).

Among persons for whom information is available, dates that illness was diagnosed ranged from March 28, 2012 to October 6, 2012. Twenty ill persons were hospitalized. Nine of the illnesses were related to a pregnancy; three of these were diagnosed in newborns. The other 13 ill persons ranged in age from 30 years to 87 years, with a median age of 77 years, and 54% were female. Four deaths were reported, one each from Minnesota, New York, Nebraska, and California. In Nebraska and California, public health officials determined that the deaths were related to listeriosis. In Minnesota and New York, public health officials did not report listeriosis as a cause of death because it was not listed as such on the death certificates. One fetal loss also was reported.

Investigation of the Outbreak

Epidemiologic, laboratory, and traceback investigations conducted by officials in local, state, and federal public health, agriculture, and regulatory agencies indicated that Frescolina Marte brand ricotta salata cheese imported from Italy and distributed by Forever Cheese, Inc. was the likely source of this outbreak of listeriosis.

In interviews, ill persons answered questions about foods consumed and other exposures in the month before becoming ill. Twelve (80%) of 15 ill persons interviewed using the Listeria Initiative questionnaire reported consuming a soft cheese. Ten (91%) of 11 ill persons who could provide information about packaging of cheeses reported consuming cheese that had been cut and repackaged at a retail location. Seven cases were linked to consumption of Frescolina Marte brand ricotta salata.

The investigation was complex because ill persons reported consuming many different cheese brands and types from many different retail locations. No one cheese was initially reported by the majority of ill persons, suggesting that cross-contamination of other cheeses through cutting boards or utensils played a role. The investigation focused on identifying intact cheeses shipped to multiple retail locations where, in the cutting process, they could have cross-contaminated other cheeses purchased by ill persons.

FDA isolated the outbreak strain of Listeria from a sample of uncut Frescolina Marte brand ricotta salata cheese, which was imported from Italy and distributed by Forever Cheese, Inc. The outbreak strain was also isolated from other types of soft cheese that had already been cut and repackaged.

Progression of the Outbreak Investigation  ⇑

November 16, 2012

Final Case Count Update

No new cases were reported since the previous case count update on October 26, 2012. A total of 22 persons infected with the outbreak-associated strain of Listeria monocytogenes were reported from 13 states and the District of Columbia. 

October 26, 2012

Case Count Update

A total of 22 persons infected with the outbreak-associated strain of Listeria monocytogenes have been reported from 13 states and the District of Columbia. The 2 new cases are from Virginia (1) and Massachusetts (1).

Among persons for whom information is available, dates when clinical specimens were collected range from March 28, 2012 to October 6, 2012. Twenty ill persons reported being hospitalized. Nine of the illnesses were related to a pregnancy; three of these illnesses were diagnosed in newborns. The other 13 ill persons range in age from 30 years to 87 years, with a median age of 77 years, and 54% of them are female.

Four deaths have been reported, one each from Minnesota, New York, Nebraska, and California. Listeriosis did not contribute to the death in Minnesota, but contributed to at least two of the other deaths. One fetal loss also has been reported.

Results of testing of clinical specimens that were collected after October 8, 2012 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. The recalled cheese should be off store shelves now because the recall began on September 10, 2012, and was expanded on September 14, 2012. However, more ill persons may be reported because up to 2 months can elapse between eating contaminated food and developing listeriosis.

October 12, 2012

Case Count Update

A total of 20 persons infected with the outbreak-associated strain of Listeria monocytogenes have been reported from 12 states and the District of Columbia. The two new cases are from California.

Among persons for whom information is available, dates when clinical specimens were collected range from March 28, 2012 to September 19, 2012. Nineteen ill persons reported being hospitalized. Nine of the illnesses were related to a pregnancy; three of these illnesses were diagnosed in newborns. The other 11 ill persons range in age from 30 years to 87 years, with a median age of 77 years, and 55% of them are female.

Four deaths have been reported, one each from Minnesota, New York, Nebraska, and California. Listeriosis did not contribute to the death in Minnesota, but contributed to at least two of the other deaths. One fetal loss also has been reported.

Results of testing of clinical specimens that were collected after September 24, 2012 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. The recalled cheese should be off store shelves now because the recall began on September 10, 2012, and was expanded on September 14, 2012. However, more ill persons may be reported because up to 2 months can elapse between eating contaminated food and developing listeriosis.

September 27, 2012

Case Count Update

A total of 18 persons infected with the outbreak-associated strain of Listeria monocytogenes have been reported from 12 states and the District of Columbia. The 3 new cases are from New Jersey (2) and Pennsylvania (1).

Among persons for whom information is available, dates when clinical specimens were collected range from March 28, 2012 to September 5, 2012. All 18 ill persons reported being hospitalized. Six of the illnesses were related to a pregnancy; two of these illnesses were diagnosed in newborns. The other 12 ill persons range in age from 30 years to 87 years, with a median age of 75 years, and 58% percent of them are female.

Three deaths have been reported, one each from Nebraska, New York, and Minnesota. Listeriosis did not contribute to the death in Minnesota, but contributed to at least one of the other deaths. One fetal loss has been reported.

Results of testing of clinical specimens that were collected after September 8, 2012 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. The recalled cheese should be off store shelves now because the recall began on September 10, 2012, and was expanded on September 14, 2012. However, more ill persons may be reported because up to 2 months can elapse between eating contaminated food and developing listeriosis.

September 21, 2012

Case Count Update

A total of 15 persons infected with the outbreak strain of Listeria monocytogenes have been reported from 12 states and the District of Columbia. This includes one new case from Washington state.

Among persons for whom information is available, illness onset dates range from March 28, 2012 to August 30, 2012. All 15 ill persons reported being hospitalized. Four of the illnesses were related to a pregnancy; two of these illnesses were diagnosed in newborns. The other 11 ill persons range in age from 30 years to 87 years, with a median age of 77 years, and 64% percent of them are female.  No fetal losses have been reported. Three deaths have been reported. Listeriosis contributed to at least one of the deaths in Nebraska and New York, but did not contribute to the death in Minnesota.

Results of testing of clinical specimens that were collected after September 4, 2012 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported.

Initial Announcement

September 11, 2012

CDC is collaborating with public health and regulatory officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Listeria monocytogenes infections (listeriosis). Joint investigation efforts indicate that ricotta salata cheese is the likely source.

Public health investigators are using DNA “fingerprints” of Listeria obtained through diagnostic testing with pulsed-field gel electrophoresis, or PFGE, to identify cases of illness that may be part of this outbreak. They are using data from PulseNet, the national subtyping network made up of state and local public health laboratories and federal food regulatory laboratories that performs molecular surveillance of foodborne infections.

A total of 14 persons infected with the outbreak strain of Listeria monocytogenes have been reported from 11 states and the District of Columbia. The number of ill people identified in each location is as follows: California (1), Colorado (1), District of Columbia (1), Maryland (3), Minnesota (1), Nebraska (1), New Jersey (1), New Mexico (1), New York (1), Ohio (1), Pennsylvania (1), and Virginia (1).

Among persons for whom information is available, dates that illness was diagnosed range from March 28, 2012 to August 30, 2012. All 14 ill persons were hospitalized. Four of the illnesses were related to a pregnancy; two of these were diagnosed in newborns. The other 10 ill persons ranged in age from 56 years to 87 years, with a median age of 79 years, and 55% were female. No fetal losses have been reported. Three deaths have been reported; one each in Minnesota, Nebraska, and New York. Listeriosis contributed to at least one of the deaths in Nebraska and New York, but did not contribute to the death in Minnesota.

The outbreak can be visually described with a chart showing the number of persons who were diagnosed each day. This chart is called an epidemic curve or epi curve. Clinical specimens that were collected after August 26, 2012 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported.

About 800 laboratory-confirmed cases of listeriosis are reported each year in the United States and typically 3 or 4 outbreaks are identified and reported to CDC. Some foods that have been linked to outbreaks in recent years are Mexican-style soft cheeses, cantaloupe, sprouts, celery, and ready-to-eat deli meat.

Investigation of the Outbreak

Epidemiologic, laboratory, and traceback investigations conducted by officials in local, state, and federal public health, agriculture, and regulatory agencies indicate that imported Marte brand Frescolina ricotta salata cheese distributed by Forever Cheese, Inc. is the likely source of this outbreak of listeriosis. In interviews, ill persons answered questions about foods consumed and other exposures in the month before becoming ill. Twelve (86%) of 14 ill persons interviewed reported consuming a soft cheese. All six ill persons who could provide information about packaging of cheeses reported consuming cheese that had been cut and repackaged at a retail location. The investigation is complex because ill persons reported consuming many different cheeses from many different retail locations. No one cheese was reported by the majority of ill persons, suggesting that cross-contamination of other cheeses through cutting boards and utensils may have played a role. The investigation focused on identifying intact cheeses shipped to multiple retail locations where ill persons purchased cut and repackaged cheese.

FDA identified the outbreak strain of Listeria monocytogenes bacteria in a sample of uncut imported Frescolina Marte brand ricotta salata cheese distributed by Forever Cheese, Inc. FDA is working closely with CDC, the firm involved, and public health authorities in states where illnesses occurred to determine the exact cause of contamination.

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