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EpiCenter is a collection of epidemiological cases investigated by public health agencies in Texas. It's focus is to bring awareness to the public regarding current disease information and how public health professionals deal with outbreaks and events on a day to day basis.

Periodically, new investigations will be posted highlighting a recent development or incident that is of public interest in terms of needed awareness and possible prevention.

Queso fresco (sometimes known as queso blanco) is a creamy, soft, and mild unaged white cheese that originated in Mexico. It is made by pressing the whey from cottage cheese. It is very similar to cheeses called pot cheese and farmer cheese and has also been compared to Indian paneer. It is considered to be one of the easiest cheeses to make. It is often used as a topping for spicy Mexican dishes such as enchiladas and empanadas as well as filling for rellenos. (from Wikipedia).

Queso fresco–in its unpasteurized state–along with lunchmeats, hotdogs, unpasteurized milk and soft cheeses, and vegetables can harbor a bacteria, Listeria monocytogenes, that is the cause of the disease Listeriosis. The bacteria can survive in the soil, water, plants, animals and people. Listeriosis can cause a variety of symptoms, but the most common are gastrointestinal illness, meningoencephalitis (fever, headache, nausea, vomiting) and septicemia (fever, aches, bacteria in the blood). The most serious effects are on the elderly (>60 years), immuno-compromised individuals, and fetuses. In the last four (4) years there have been 37 cases of queso fresco linked Listeriosis in Texas which doesn’t seem like a lot, but these are the reported cases, those that have laboratory confirmation. L. monocytogenes isolates sent to the DSHS laboratory in Austin are tested using molecular biology methods (Pulse Field Gel Electrophoresis) to determine strain type

The real problem is the majority of its victims are newborn infants who have acquired the pathogen as fetuses after their mothers’ ingestion of contaminated food. Fully 30% of infants who contract this disease die, with 50% mortality if they are displaying symptoms within the first four (4) days after birth. Additionally, there are reported cases of miscarriages and stillbirths in infected mothers.

In Texas, the majority of the listeriosis cases are the result of the consumption of unpasteurized queso fresco purchased in Mexico at street markets and transported across the border for personal consumption. While this purchase and transportation is completely legal, some of the cheese is subsequently sold illegally in flea and farmer’s markets in the U.S. These sales are not approved by the FDA or the Texas Department of State Health Services.

Queso Fresco associated Listeriosis in Texas, the facts
2003 – 2007 (to date) Summary

• 37 cases
• 12 non-pregnant adults, 25 mother/baby pairs
• 3 adult deaths (not pregnancy related), 1 infant death
• 4 miscarriages
• 11 premature deliveries
• 34 of the cases were Hispanic
• 29 reported eating queso fresco
• 22 cases in Hidalgo and Cameron Counties, 14 cases in Harris County

What should you do about it? Carefully following food safety precautions (see below) can substantially reduce your chances of becoming ill. Thorough cooking will destroy Listeria on foods. People at high risk (see above) should refrain from eating deli items, unless they are reheated until steaming hot; soft cheeses (such as feta, Brie, Camembert, blue-veined cheeses, and "queso blanco" or "queso fresco"); refrigerated pâtés or meat spreads; and, smoked seafood (often labeled as "nova-style," "lox," "kippered," "smoked," or "jerky"), unless it is in a cooked dish. Perishable or ready-to-eat foods should be used as soon as possible.

For more information on Listeriosis.