A total of 8 persons infected with the outbreak strain of Listeria monocytogenes have been reported from two states. Seven were from Maryland and one from California. Among persons for whom information is available, dates that illness was diagnosed range from August 1, 2013 to November 27, 2013. Seven of the eight ill persons were hospitalized. Five of the illnesses were related to a pregnancy; two of these were diagnosed in two mother–newborn pairs, and one in only the newborn. The three other illnesses occurred among adults. One death was reported in California. All ill persons were reported to be of Hispanic ethnicity.
Clinical specimens that were collected after February 1, 2014 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 3 weeks.
In interviews, ill persons answered questions about foods consumed and other exposures in the month before becoming ill. All patients in Maryland reported consuming soft or semi-soft Hispanic-style cheese and all shopped at different locations of same food store chain (Chain A). Testing of cheese products collected from Chain A stores was performed in Maryland and Virginia.
Virginia’s Division of Consolidated Laboratory Services (DCLS) identified the outbreak strain ofListeria monocytogenes in a sample of Caujada en Terron (fresh cheese curd) collected by the Virginia Department of Agriculture and Consumer Services (VDACS) from a Chain A store. This cheese was likely produced by Roos Foods of Kenton, Delaware and was later repackaged in the Chain A store. VDACS issued a press release on February 15, 2014 instructing persons who purchased this product not to consume the cheese and to discard any remaining product.
VDACS subsequently collected pre-packaged Caujada en Terron produced by Roos Foods from Chain A that was not repackaged in the store. The Virginia DCLS identified Listeria monocytogenesfrom these samples; a consumer advisory was issued on February 21, 2014. DNA fingerprinting and whole-genome sequencing will be performed on these isolates. In addition, the Maryland Department of Health and Mental Hygiene has tested samples of pre-packaged cheese products purchased at Chain A stores; those products produced by Roos Foods are preliminarily positive for Listeria monocytogenes. On February 19, 2014, the Maryland Department of Health and Mental Hygiene issued a warning to consumers to not eat any cheese products made by Roos Foods. Their warning stated that Roos Foods cheese products are sold under brand names Santa Rosa de Lima, Amigo, Mexicana, Suyapa, La Chapina, and La Purisima Crema Nica.
Further investigation is needed to determine the source of the patients’ illnesses, including whether the illnesses were related to food products that tested positive for Listeria.