Investigation Update: Multistate Outbreak of Listeriosis Linked to Whole Cantaloupes from Jensen Farms, Colorado
October 4, 2011
Case Count Map
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 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 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. State and local health departments in these and other states are investigating other listeriosis illnesses to determine if they are part of this outbreak.
Among persons for whom information is available, illnesses began on or after July 31, 2011. Ages range from 35 to 96 years, with a median age of 79 years. Most ill persons are over 60 years old. Forty-nine percent of ill persons are female. Among the 93 ill persons with available information on whether they were hospitalized, 91 (98%) were hospitalized. Two women were pregnant at the time of illness and the outcome of each pregnancy is 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 September 7, 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.
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 77 ill persons with available information on what they ate, 71 (92%) 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 Sept 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.
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 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 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.
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; it is recalling 594 pounds of fresh-cut cantaloupe packaged in 5-pound trays as chunks and as an ingredient in an 8-ounce mixed fruit medley.
Advice to Consumers
Contaminated cantaloupes may make people sick.
- CDC recommends that consumers not eat 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 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 in cantaloupe at room and refrigerator temperatures, and may remain in the refrigerator even after the cantaloupe has been discarded.
- 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. Do not attempt to wash off the Listeria, as it is possible the cantaloupe contains Listeria on the inside as well.
- 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 melons not part of this recall, FDA has this general advice for melon safety:
- Consumers and food preparers should wash their hands with warm water and soap for at least 20 seconds before and after handling any whole melon, such as cantaloupe, watermelon, or honeydew.
- Scrub the surface of melons, such as cantaloupes, with a clean produce brush and dry them with a clean cloth or paper towel before cutting.
- Cut melon should be promptly consumed or refrigerated at or less than 40 degrees F (32-34 degrees F is best) for no more than 7 days.
- Cut melons left at room temperature for more than 4 hours should be discarded.
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
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.