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Office of Binational Border Health

Border Infectious Disease Surveillance - Queso Fresco


The Centers for Disease Control and Prevention (CDC) estimate there are approximately 48 million cases of foodborne illness per year in the United States. Unpasteurized (raw) milk and certain derived products can harbor pathogens that would have otherwise been eliminated through the process of pasteurization. According to the CDC, more than 1,500 people became sick from drinking unpasteurized milk or eating cheese made from raw milk between 1993 and 2006 in the United States. Certain groups are considered at risk of contracting a foodborne illness, including people with weakened immune systems, pregnant women, and the elderly. BIDS aims to identify if unpasteurized cheese consumption is playing a role in the spread of disease in San Diego County.


The purpose of the Queso Fresco Enhanced Surveillance is to assess the burden of enteric illnesses that could be attributed to unpasteurized queso fresco and other Mexican-style soft cheeses. Disease investigators complete an additional questionnaire if queso fresco was consumed by the individual during the exposure period for their illness. The enteric illnesses monitored are those caused by Shiga toxin-producing E. coli (including O157), Salmonella, Shigella, Listeria, Brucella, and Hepatitis A. The questionnaires are designed to obtain detailed exposure information, including the source and location of purchase.


In 2017, there were 63 cases of foodborne illness included in enhanced surveillance for queso fresco. Instances of homemade cheese were identified in some of the cases, which helped BIDS identify opportunities for outreach and educational campaigns. The results of enhanced surveillance are also shared in quarterly meetings of the Queso Fresco Task Force. The task force is comprised of officials from the Office of Border Health and Department of Environmental Health of San Diego County, the California Department of Food and Agriculture, CDC US-Mexico Unit, and Customs and Border Protection, among others.

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