The U.S. Center for Disease Control 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 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). Listeriosis illnesses in several other states are currently being investigated by state and local health departments to determine if they are part of this outbreak.
Among persons for whom information is available, illnesses began on or after August 4, 2011. Ages range from 35 to 96 years, with a median age of 81 years old. Most ill persons are over 60 years old or have health conditions that weaken the immune system. Sixty-five percent of ill persons are female. Among the 28 ill persons with available information on whether they were hospitalized, all were hospitalized. Four deaths have been reported, one in Colorado, one in Oklahoma, and two in New Mexico.