After the final 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.