Multistate Outbreak of Listeriosis Linked to Imported Marte Brand Frescolina Ricotta Salata Cheese

CDC is collaborating with public health and regulatory officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Listeria monocytogenes infections (listeriosis). Joint investigation efforts indicate that ricotta salata cheese is the likely source.

Public health investigators are using DNA “fingerprints” of Listeria obtained through diagnostic testing with pulsed-field gel electrophoresis, or PFGE, to identify cases of illness that may be part of this outbreak. They 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 14 persons infected with the outbreak strain of Listeria monocytogenes have been reported from 11 states and the District of Columbia. The number of ill people identified in each location is as follows: California (1), Colorado (1), District of Columbia (1), Maryland (3), Minnesota (1), Nebraska (1), New Jersey (1), New Mexico (1), New York (1), Ohio (1), Pennsylvania (1), and Virginia (1).

Among persons for whom information is available, dates that illness was diagnosed range from March 28, 2012 to August 30, 2012. All 14 ill persons were hospitalized. Four of the illnesses were related to a pregnancy; two of these were diagnosed in newborns. The other 10 ill persons ranged in age from 56 years to 87 years, with a median age of 79 years, and 55% were female. No fetal losses have been reported. Three deaths have been reported; one each in Minnesota, Nebraska, and New York. Listeriosis contributed to at least one of the deaths in Nebraska and New York, but did not contribute to the death in Minnesota.

The outbreak can be visually described with a chart showing the number of persons who were diagnosed each day. This chart is called an epidemic curve or epi curve. Clinical specimens that were collected after August 26, 2012 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported.

About 800 laboratory-confirmed cases of listeriosis are reported each year in the United States and typically 3 or 4 outbreaks are identified and reported to CDC. Some foods that have been linked to outbreaks in recent years are Mexican-style soft cheeses, cantaloupe, sprouts, celery, and ready-to-eat deli meat.

Read More at the CDC Website's outbreak page.