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Multistate Outbreak of Listeriosis Linked to Whole Cantaloupes from Jensen Farms, Colorado (FINAL UPDATE)

Posted August 27, 2012 10:30 AM ET

This investigation is closed.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 website.

Highlights

Outbreak Summary

Introduction

CDC collaborated with public health officials in numerous states, including Colorado, as well as the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of listeriosis that occurred from August through October, 2011. Listeriosis is a serious infection usually caused by eating food contaminated with the bacterium Listeria monocytogenes. Investigators used DNA analysis of Listeria bacteria isolated from patients to identify cases of illness that may have been part of this outbreak. The Listeria bacteria were obtained from diagnostic testing; pulsed-field gel electrophoresis (PFGE) was used to determine DNA fingerprint patterns. Investigators 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.

After the update on December 8, investigators learned that a Listeria isolate that had been isolated from a sample of cut cantaloupe from a patient’s home during the outbreak investigation had a PFGE pattern combination that was different from the four known pattern combinations in the outbreak. A search of the PulseNet database for matching DNA fingerprint patterns from isolates collected during the outbreak time period identified one human matching isolate. The person from whom the Listeria was isolated reported eating cantaloupe before becoming ill; this case was added to the case count.

A total of 147 persons infected with any of the five outbreak-associated subtypes of Listeria monocytogenes were reported to CDC from 28 states. The number of infected persons identified in each state was as follows: Alabama (1), Arkansas (1), California (4), Colorado (40), Idaho (2), Illinois (4), Indiana (3), Iowa (1), Kansas (11), Louisiana (2), Maryland (1), Missouri (7), Montana (2), Nebraska (6), Nevada (1), New Mexico (15), New York (2), North Dakota (2), Oklahoma (12), Oregon (1), Pennsylvania (1), South Dakota (1), Texas (18), Utah (1), Virginia (1), West Virginia (1), Wisconsin (2), and Wyoming (4).

Among persons for whom information was available, reported illness onset ranged from July 31, 2011 through October 27, 2011. Ages ranged from <1 to 96 years, with a median age of 78 years. Most ill persons were over 60 years old. Fifty-eight percent of ill persons were female. Among the 145 ill persons with available information on whether they were hospitalized, 143 (99%) were hospitalized. Thirty-three outbreak-associated deaths were reported: Colorado (9), Indiana (1), Kansas (3), Louisiana (2), Maryland (1), Missouri (3), Montana (1), Nebraska (1), New Mexico (5), New York (2), Oklahoma (1), Texas (2), and Wyoming (2). Among persons who died, ages ranged from 48 to 96 years, with a median age of 81 years. In addition, one woman pregnant at the time of illness had a miscarriage. Ten deaths not attributed to listeriosis occurred among persons who had been infected with an outbreak-associated subtype. State and local public health officials reviewed causes of death listed on death certificates to determine whether to attribute these deaths to listeriosis. Deaths included in this review occurred as recently as February 29, 2012.

Seven of the illnesses were related to a pregnancy; three were diagnosed in newborns and four were diagnosed in pregnant women. One miscarriage was reported.

The outbreak can be visually described with a chart showing the number of persons who became ill each day. This chart is called an epidemic curve or epi curve. Please see the description of the steps in a foodborne outbreak investigation for more details.

About 800 laboratory-confirmed cases of Listeria infection are reported each year in the United States and typically 3 or 4 outbreaks are identified. The foods that typically cause these outbreaks have been Mexican-style soft cheeses made with unpasteurized milk, deli meats, and hot dogs. In the past, produce was not often identified as a source, but sprouts caused an outbreak in 2009, and precut celery caused an outbreak in 2010.

Investigation of the Outbreak

Collaborative investigations by local, state, and federal public health and regulatory agencies indicated that the source of the outbreak was whole cantaloupe grown at Jensen Farms’ production fields in Granada, Colorado. Among the 144 ill persons with available information on what they ate, 134 (93%) reported consuming cantaloupe in the month before illness onset. Several ill persons remembered the type of cantaloupes they had eaten and said they were Rocky Ford cantaloupes, which are grown in the Rocky Ford region of southeastern Colorado. Source tracing of the cantaloupes that ill persons ate indicated that they came from Jensen Farms, and were marketed as being from the Rocky Ford region. These cantaloupes were shipped from July 29 through September 10 to at least 24 states , with possible further distribution.

The Colorado Department of Public Health and Environment isolated Listeria monocytogenes from cantaloupe samples collected from grocery stores and from ill persons’ homes. Colorado state officials determined that these cantaloupes came from Jensen Farms. FDA isolated Listeria monocytogenes outbreak subtypes from samples from equipment and cantaloupe from the Jensen Farms’ packing facility in Granada, Colorado. FDA worked closely with CDC, the firms involved, and public health authorities in states where illnesses occurred to determine the cause of contamination. Cantaloupes from other farms were not linked to this outbreak

 

August 27, 2012 (FINAL Update Addendum)

Final Case Count Update
  • This multistate outbreak of Listeria monocytogenes infections (listeriosis) ended in October, 2011.
  • After the final update on December 8, a fifth outbreak-associated subtype of Listeria was isolated from a sample of cantaloupe collected during the investigation.
  • The fifth subtype matches that of Listeria isolated from one patient. This patient's illness had been reported, but had not previously been linked to the outbreak. Therefore, this case has been added to the number of outbreak-associated illnesses. This brings the total number of outbreak-associated illnesses to 147 persons infected with any of the five outbreak-associated subtypes of Listeria. These persons lived in 28 states.
  • The number of outbreak-associated deaths has increased by three since December 8, 2011. In total, 33 deaths from outbreak-associated cases of listeriosis have been reported to CDC. In addition, one woman pregnant at the time of illness had a miscarriage.
  • Ten other deaths not attributed to listeriosis occurred among persons who had been infected with an outbreak-associated subtype. State and local public health officials reviewed causes of death listed on death certificates to determine whether to attribute these deaths to listeriosis. Deaths included in this review occurred as recently as February 29, 2012.
  • Timeline of Events: Multistate Outbreak of Listeriosis Linked to Whole Cantaloupes from Jensen Farms, Colorado—United States, 2011

December 8, 2011 (FINAL Update)

Case Count Update

November 2, 2011

Case Count Update

October 25, 2011

Case Count Update
  • As of 9am EDT on October 24, 2011, a total of 133 persons infected with any of the four outbreak-associated strains of Listeria monocytogenes have been reported to CDC from 26 states. 
  • Twenty-eight deaths have been reported. In addition, one woman pregnant at the time of illness had a miscarriage.

October 18, 2011

Case Count Update
  • As of 9am EDT on October 17, 2011, a total of 123 persons infected with any of the four outbreak-associated strains of Listeria monocytogenes have been reported to CDC from 26 states. Pennsylvania has reported their first case since the last CDC update.
  • Twenty-five deaths have been reported. In addition, one woman pregnant at the time of illness had a miscarriage.

October 12, 2011

Case Count Update
  • As of 9am EDT on October 11, 2011, a total of 116 persons infected with any of the four outbreak-associated strains of Listeria monocytogenes have been reported to CDC from 25 states.  All illnesses started on or after July 31, 2011. The number of infected persons identified in each state is as follows: Alabama (1), Arkansas (1), California (1), Colorado (34), Idaho (1), Illinois (1), Indiana (3), Iowa (1), Kansas (7), Louisiana (2), Maryland (1), Missouri (4), Montana (1), Nebraska (6), New Mexico (13), New York (1), North Dakota (1), Oklahoma (11), Oregon (1), South Dakota (1), Texas (17), Virginia (1), West Virginia (1), Wisconsin (2), and Wyoming (3). 
  • Twenty-three deaths have been reported: 5 in Colorado, 1 in Indiana, 2 in Kansas, 2 in Louisiana, 1 in Maryland, 1 in Missouri, 1 in Nebraska, 5 in New Mexico, 1 in New York, 1 in Oklahoma, 2 in Texas, and 1 in Wyoming. In addition, one woman pregnant at the time of illness had a miscarriage.

October 7, 2011

Case Count Update
  • As of 9am EDT on October 6, 2011, a total of 109 persons infected with any of the four outbreak-associated strains of Listeria monocytogenes have been reported to CDC from 24 states.  All illnesses started on or after July 31, 2011. The number of infected persons identified in each state is as follows: Alabama (1), Arkansas(1), California (1), Colorado (32), Idaho (1), Illinois (1), Indiana (2), Iowa (1), Kansas (7), Maryland (1), Missouri (3), Montana (1), Nebraska (6), New Mexico (13), New York (1), North Dakota (1), Oklahoma (11), Oregon (1),  South Dakota (1), Texas (16), Virginia (1), West Virginia (1), Wisconsin (2), and Wyoming (3).
  • Twenty-one deaths have been reported: 5 in Colorado, 1 in Indiana, 2 in Kansas, 1 in Maryland, 1 in Missouri, 1 in Nebraska, 5 in New Mexico, 1 in New York, 1 in Oklahoma, 2 in Texas, and 1 in Wyoming. In addition, one woman pregnant at the time of illness had a miscarriage.

October 4, 2011

Case Count Update
  • As of 11am EDT on October 3, 2011, a total of 100 persons infected with any of the four outbreak-associated strains of Listeria monocytogenes have been reported to CDC from 20 states.  All illnesses started on or after July 31, 2011. The number of infected persons identified in each state is as follows: Alabama (1), Arkansas (1) California (1), Colorado (30), Idaho (1), Illinois (1), Indiana (2), Kansas (7), Maryland (1), Missouri (3), Montana (1), Nebraska (6), New Mexico (13), North Dakota (1), Oklahoma (11), Texas (14), Virginia (1), West Virginia (1), Wisconsin (2), and Wyoming (2).
  • Eighteen deaths have been reported: 5 in Colorado, 2 in Kansas, 1 in Maryland, 1 in Missouri, 1 in Nebraska, 5 in New Mexico, 1 in Oklahoma, and 2 in Texas.

September 30, 2011

Case Count Update
  • As of 11am EDT on September 29, 2011, a total of 84 persons infected with any of the four outbreak-associated strains of Listeria monocytogenes have been reported to CDC from 19 states.  All illnesses started on or after July 31, 2011. The number of infected persons identified in each state is as follows: Alabama (1), Arkansas (1) California (1), Colorado (17), Illinois (1), Indiana (2), Kansas (5), Maryland (1), Missouri (3), Montana (1), Nebraska (6), New Mexico (13), North Dakota (1), Oklahoma (11), Texas (14), Virginia (1), West Virginia (1), Wisconsin (2), and Wyoming (2). 
  • Fifteen deaths have been reported: 3 in Colorado, 1 in Kansas, 1 in Maryland, 1 in Missouri, 1 in Nebraska, 5 in New Mexico, 1 in Oklahoma, and 2 in Texas.

September 27, 2011

Case Count Update
  • As of 11am EDT on September 26, 2011, a total of 72 persons infected with the four outbreak-associated strains of Listeria monocytogenes have been reported to CDC from 18 states.  All illnesses started on or after July 31, 2011. The number of infected persons identified in each state is as follows: California (1), Colorado (15), Florida (1), Illinois (1), Indiana (2), Kansas (5), Maryland (1), Missouri (1), Montana (1), Nebraska (6), New Mexico (10), North Dakota (1), Oklahoma (8), Texas (14), Virginia (1), West Virginia (1), Wisconsin (2), and Wyoming (1). 
  • Thirteen deaths have been reported: 2 in Colorado, 1 in Kansas, 1 in Maryland, 1 in Missouri, 1 in Nebraska, 4 in New Mexico, 1 in Oklahoma, and 2 in Texas.

September 21, 2011

Case Count Update

As of 5pm EDT on September 20, 2011, a total of 55 persons infected with the 4 outbreak-associated strains of Listeria monocytogenes have been reported from 14 states.  All illnesses started on or after August 4, 2011. The number of infected persons identified in each state is as follows:  California (1), Colorado (14), Illinois (1), Indiana (1), Maryland (1), Montana (1), Nebraska (4), New Mexico (10), Oklahoma (8), Texas (9), Virginia (1), West Virginia (1), Wisconsin (2), and Wyoming (1). 

September 19, 2011

A total of 35 persons infected with the outbreak-associated strains of Listeria monocytogenes have been reported from 10 states. All illnesses started on or after August 4, 2011. The number of infected persons identified in each state is as follows: California (1), Colorado (12), Illinois (1), Indiana (1), Montana (1), Nebraska (4), New Mexico (5), Oklahoma (6), Texas (3), and West Virginia (1).

September 14, 2011

Today's Highlights
  • A total of 22 persons infected with the outbreak-associated strains of Listeria monocytogenes have been reported from 7 states. The number of infected persons identified in each state is as follows: Colorado (12), Indiana (1), Nebraska (1), New Mexico (4), Oklahoma (1), Texas (2), and West Virginia (1). Two deaths have been reported, one in Colorado and one in New Mexico.
  • Collaborative investigative efforts of state, local, and federal public health and regulatory agencies have linked this outbreak to eating whole cantaloupe from Jensen Farms, of Granada, Colorado.
  • On September 14, 2011, FDA issued a press release to announce that Jensen Farms issued a voluntary recall of Rocky Ford Cantaloupe because the cantaloupes have the potential to be contaminated with Listeria and may be linked to a multi-state outbreak of listeriosis.
  • CDC recommends that persons at high risk for listeriosis, including older adults, persons with weakened immune systems, and pregnant women, do not eat Rocky Ford cantaloupes from Jensen Farms. Other consumers who want to reduce their risk of Listeria infection should not eat Rocky Ford cantaloupes from Jensen Farms.
  • Even if some of the cantaloupe has been eaten without becoming ill, dispose of the rest of the cantaloupe immediately. Listeria bacteria can grow in the cantaloupe at room and refrigerator temperatures.

September 13, 2011

Today's Highlights
  • A total of 16 persons infected with the outbreak-associated strains of Listeria monocytogenes have been reported from 5 states.  All illnesses started on or after August 15, 2011. The number of infected persons identified in each state is as follows:  Colorado (11), Indiana (1), Nebraska (1), Oklahoma (1), and Texas (2). 
  • Epidemiologic, traceback, and laboratory investigations have linked this outbreak to eating cantaloupes marketed as coming from the Rocky Ford region of Colorado.
  • CDC recommends that persons at high risk for listeriosis, including older adults, persons with weakened immune systems, and pregnant women, do not eat cantaloupes marketed as coming from the Rocky Ford region of Colorado.
  • FDA is working closely with CDC, the firms involved, and public health authorities in states where illnesses occurred to determine the exact source of contamination.
  • Suspected cases are being investigated in several other states.

Introduction

September 11, 2012

CDC is collaborating with public health officials in several states, including Colorado, and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of listeriosis. Listeriosis is a serious infection usually caused by eating food contaminated with the bacterium Listeria monocytogenes. Investigators are using DNA analysis of Listeria isolated from patients to identify cases of illness that may be part of this outbreak. The Listeria bacteria are obtained from diagnostic testing; pulsed-field gel electrophoresis (PFGE) is used to determine DNA fingerprint patterns. Investigators 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 15 persons infected with the outbreak strain of Listeria monocytogenes have been reported from 4 states. All illnesses started on or after August 15, 2011. The number of infected persons identified in each state is as follows:  Colorado (11), Nebraska (1), Oklahoma (1), and Texas (2). Listeriosis illnesses in several other states are currently being investigated by state and local health departments to determine if these illnesses are part of this outbreak.

Among persons for whom information is available, illnesses began on or after August 15, 2011. Ages range from 38 to 96 years, with a median age of 84 years old. Most ill persons are over 60 years old or have health conditions that weaken the immune system. Seventy-three percent of ill persons are female. All 15 (100%) patients were hospitalized, and one death has been reported.

The outbreak can be visually described with a chart showing the number of persons who became ill each day. This chart is called an epidemic curve or epi curve. Illnesses that occurred after August 26, 2011, might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. Please see the description of the steps in a foodborne outbreak investigation for more details.

About 800 cases of Listeria infection are diagnosed each year in the United States, along with 3 or 4 outbreaks of Listeria-associated foodborne illness. The typical foods that cause these outbreaks have been deli meats, hot dogs, and Mexican-style soft cheeses made with unpasteurized milk. Produce is not often identified as a source, but sprouts caused an outbreak in 2009, and celery caused an outbreak in 2010.

Investigation of the Outbreak

Ongoing collaborative investigations by local, state, and federal public health and regulatory agencies indicate the likely source of the outbreak is a type of cantaloupe, called Rocky Ford cantaloupes, which are grown in the Rocky Ford region of southeastern Colorado. These cantaloupes were harvested in August and September, distributed widely in the United States, and are currently available in grocery stores.  Ill persons were interviewed about exposures during the month before becoming ill; investigators compared their responses to persons with listeriosis reported through the CDC Listeria Initiative, whose illnesses were not part of this outbreak. Preliminary results strongly suggest that illnesses are linked to consumption of cantaloupes.  Several ill persons who remembered the type of cantaloupe said they were Rocky Ford cantaloupes.  Product traceback information indicated these cantaloupes were marketed as cantaloupes harvested in the Rocky Ford region.

Laboratory testing by the Colorado Department of Public Health and Environment identified Listeria monocytogenes bacteria on cantaloupe collected from grocery stores and from an ill person’s home. Product traceback information from Colorado State officials indicated these cantaloupes were harvested in the Rocky Ford region.  FDA is working closely with CDC, the firms involved, and public health authorities in states where illnesses occurred to determine the exact source of contamination.

On September 9, the Colorado Department of Public Health and Environment advised persons in Colorado at high risk for severe listeriosis to avoid eating cantaloupes.  CDC now advises persons throughout the mainland United States and at high risk for listeriosis, including older adults, persons with weakened immune systems, and pregnant women, to not eat cantaloupes marketed as coming from the Rocky Ford region of Colorado.

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