Listeria (Listeriosis)

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

Persons infected with the outbreak-associated strains of Listeria monocytogenes, by date of illness onset*

Chart showing bar graph indicating numbers of persons infected with the outbreak-associated strains of Listeria monocytogenes, by date of illness onset

*n= 99 for whom information on illness onset was reported to CDC by 11am EDT on October 3, 2011

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.