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Investigation Update: Multistate Outbreak of Listeriosis Linked to Whole Cantaloupes from Jensen Farms, Colorado

November 2, 2011


CDC is collaborating with public health officials in numerous 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 bacteria 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.

As of 9am EDT on November 1, 2011, a total of 139 persons infected with any of the four outbreak-associated strains of Listeria monocytogenes have been reported to CDC from 28 states.  The number of infected persons identified in each state is as follows: Alabama (1), Arkansas (1), California (2), Colorado (39), Idaho (2), Illinois (3), Indiana (3), Iowa (1), Kansas (10), Louisiana (2), Maryland (1), Missouri (6), Montana (1), Nebraska (6), Nevada (1), New Mexico (15), New York (2), North Dakota (2), Oklahoma (11), Oregon (1), Pennsylvania (1), South Dakota (1), Texas (18), Utah (1), Virginia (1), West Virginia (1), Wisconsin (2), and Wyoming (4). Nevada and Utah have reported their first case each since the last CDC update. Among persons for whom information is available, reported illness onset ranges from July 31, 2011 through October 21, 2011. Ages range from <1 to 96 years, with a median age of 77 years. Most ill persons are over 60 years old. Fifty-seven percent of ill persons are female. Among the 134 ill persons with available information on whether they were hospitalized, 132 (99%) were hospitalized. State and local health departments in these and other states are investigating other listeriosis illnesses to determine if they are part of this outbreak.

Twenty-nine deaths have been reported: Colorado (8), Indiana (1), Kansas (3), Louisiana (2), Maryland (1), Missouri (2), Nebraska (1), New Mexico (5), New York (2), Oklahoma (1), Texas (2), and Wyoming (1). Among persons who died, ages range 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.

Five of the illnesses were related to a pregnancy; two were diagnosed in newborns and three were diagnosed in pregnant women. One miscarriage has been reported. Other outcomes are being monitored.

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 October 6, 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 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 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.

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Investigation of the Outbreak

Ongoing collaborative investigations by local, state, and federal public health and regulatory agencies indicate that the source of the outbreak is whole cantaloupe grown at Jensen Farms’ production fields in Granada, Colorado. Among the 103 ill persons with available information on what they ate, 97 (94%) reported consuming cantaloupes in the month before illness onset. Several ill persons remembered the type of cantaloupe 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.

Laboratory testing by the Colorado Department of Public Health and Environment identified Listeria monocytogenes bacteria on cantaloupes collected from grocery stores and from ill persons’ homes. Product traceback information from Colorado state officials indicated that these cantaloupes also came from Jensen Farms. Laboratory testing by FDA has identified L. monocytogenes outbreak strains in samples from equipment and cantaloupe at the Jensen Farms’ packing facility in Granada, Colorado. FDA is working closely with CDC, the firms involved, and public health authorities in states where illnesses occurred to determine the exact cause of contamination. Cantaloupes from other farms have not been linked to this outbreak.

Although Jensen Farms issued a voluntary recall of Rocky Ford-brand cantaloupes on September 14 and the recalled cantaloupe should be off store shelves, more ill persons may be reported because of the time lag between diagnosis and laboratory confirmation and also because up to 2 months can elapse between eating contaminated food and developing listeriosis. 

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Clinical Features/Signs and Symptoms

Listeriosis is a serious infection caused by eating food contaminated with the bacterium Listeria monocytogenes. The disease primarily affects older adults, persons with weakened immune systems, pregnant women, and newborns.  Less commonly, persons without these risk factors can be affected.

A person with listeriosis usually has fever and muscle aches, often preceded by diarrhea or other gastrointestinal symptoms. Almost everyone who is diagnosed with listeriosis has invasive infection (meaning that the bacteria spread from their intestines to the bloodstream or other body sites).

Listeriosis is treated with antibiotics. Persons in the high-risk category, including older adults, persons with weakened immune systems, and pregnant women, who experience flu-like symptoms within 2 months after eating contaminated food should seek medical care and tell the physician or health care provider about eating the contaminated food.

The symptoms vary with the infected person:

  • High-risk persons other than pregnant women: Symptoms can include fever, muscle aches, headache, stiff neck, confusion, loss of balance, and convulsions.
  • Pregnant women: Pregnant women typically experience only a mild, flu-like illness. However, infection during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.
  • Healthy persons. Healthy persons occasionally develop invasive listeriosis. In addition, persons exposed to a very large dose of Listeria bacteria can develop a non-invasive illness with diarrhea and fever (meaning that the bacteria do not spread into their blood stream or other sites).

If a person has eaten food contaminated with Listeria bacteria and does not have any symptoms, most experts believe that no tests or treatment are needed, even for persons at higher risk for listeriosis.

More general information about listeriosis can be found at the CDC's Listeriosis webpage.

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On September 14, 2011, FDA issued a press release to announce that Jensen Farms issued a voluntary recall of its Rocky Ford-brand cantaloupes after they were linked to a multistate outbreak of listeriosis.  On September 23, 2011, FDA issued a press release  to announce a recall from Carol’s Cuts LLC, a Kansas food processor. The company is recalling 594 pounds of fresh-cut cantaloupe, which were packaged in 5-pound trays as chunks and as an ingredient in an 8-ounce mixed fruit medley, because the cantaloupes originated from Jensen Farms.  On October 6, FDA posted a press release that announced a recall from Fruit Fresh Up, Inc., a New York food processor. The company is recalling 4,800 individual packages of fresh cut cantaloupe and cut mixed fruit containing cantaloupe, because the cantaloupe originated from Jensen Farms. The fresh cut fruit subject to this recall was sold between August 31 and September 11, 2011. Given that the Jensen Farms’ recall has been in effect for more than three weeks and that the shelf life of a cantaloupe is approximately two weeks, it is expected that all of the recalled whole Jensen Farms cantaloupes have been removed from the marketplace.

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Advice to Consumers

Contaminated cantaloupes may make people sick.

a picture showing the label found on the contaminated cantaloupes
  • CDC recommends that consumers not eat whole or pre-cut Rocky Ford-brand cantaloupe from Jensen Farms. This is especially important for older adults, persons with weakened immune systems, and pregnant women.  
  • Even if some of the cantaloupe has been eaten without anyone becoming ill, the rest of the cantaloupe should be disposed of immediately.
  • The recalled cantaloupes from Jensen Farms may have sticker that looks like the image to the right. Not all of the recalled cantaloupes are labeled with a sticker. Consumers can consult the retailer if they have questions about the origin of a cantaloupe.
  • When in doubt, throw it out (See disposal recommendations below)

Who is most at risk?

  • Listeriosis primarily affects older adults, persons with weakened immune systems, pregnant women, and newborns.
  • Persons who think they might have become ill from eating contaminated cantaloupe should consult their doctor immediately. People can develop listeriosis up to two months after eating contaminated food.
  • Recommendations for preventing listeriosis from foods other than cantaloupes are available at CDC's Listeriosis webpage on prevention.

Contaminated cantaloupes that are under recall may still be in consumers' homes.

  • Listeria bacteria can grow on cut cantaloupe at room and refrigerator temperatures.
  • Follow these simple steps if Rocky Ford-brand cantaloupes from Jensen Farms are in your home, or were in your home:
    • Dispose of cantaloupes in a closed plastic bag placed in a sealed trash can. This will prevent people and animals from eating them.
    • Wash the inside walls and shelves of the refrigerator, cutting boards and countertops; then sanitize them with a solution of one tablespoon of chlorine bleach to one gallon of hot water;
    • Dry with a clean cloth or paper towel that has not been previously used.
    • Wipe up spills in the refrigerator immediately and clean the refrigerator regularly.
    • Always wash hands with warm water and soap following the cleaning and sanitation process.

For more information about listeriosis and recommendations to reduce your risk of getting listeriosis go to CDC's Listeriosis webpage on prevention.

For more information on produce safety go to FDA's Produce Safety webpage 

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Key Resources

CDC's Role in Food Safety

CDC leads federal efforts to gather data on foodborne illnesses, investigate foodborne outbreaks and monitor the effectiveness of prevention and control efforts. CDC is not a food safety regulatory agency but works closely with the food safety regulatory agencies, in particular, with FDA and U.S. Department of Agriculture's Food Safety and Inspection Service. CDC also plays a key role in building state and local health department epidemiology, laboratory and environmental health capacity to support foodborne disease surveillance and outbreak response. Notably, CDC data can be used to help document the effectiveness of regulatory interventions.

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Previous Updates

October 25, 2011

October 18, 2011

October 12, 2011

October 7, 2011

October 4, 2011

September 30, 2011

September 27, 2011

September 19, 2011

September 14, 2011

September 13, 2011

September 12, 2011

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