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Epidemiologic Notes and Reports Listeriosis Outbreak Associated with Mexican-Style Cheese -- California

Between January 1, and June 14, 1985, 86 cases of Listeria monocytogenes infection were identified in Los Angeles and Orange Counties, California. Fifty-eight of the cases were among mother-infant pairs. Twenty-nine deaths have occurred: eight neonatal deaths, 13 stillbirths, and eight non-neonatal deaths. An increased occurrence of listeriosis was first noted at the Los Angeles County-University of Southern California Medical Center; all cases were in pregnant Hispanics, and all appeared to be community-acquired. A systematic review of laboratory records at hospitals in Los Angeles and Orange County identified additional cases throughout the area.

An analysis of Los Angeles County cases showed that 45 (63%) of the Listeria cases were among mother-newborn pairs. Most (70%) of these women had a prior febrile illness or were febrile on admission to the hospital. Forty-two of the neonatal patients had onset of disease within 24 hours of birth, and all isolates available for testing were serotype 4b. Three of the neonatal patients had late onset disease; only one of the two isolates available for testing was serotype 4b.

The mothers ranged in age from 15 years to 43 years (mean 28 years). The mean gestational age was 33 weeks. Forty-three (96%) of these pairs were Hispanic; one was white; and one was Asian. Table 2 shows the age and race data on the 26 nonperinatal cases.

A case-control study was conducted among the Los Angeles County Hispanic patients who had early onset; mothers with listeriosis were more likely to have consumed Mexican-style fresh cheeses than age-matched controls, Hispanic women who had delivered at the same hospital within 10 days of their matched case (odds ratio: 5.5; 95% confidence interval: 1.2-24.8). Consumption of cheese from one particular manufacturer, Jalisco Products, Inc., was significantly associated with risk of disease (odds ratio: 7.5; 95% confidence interval: 1.4-94.6).

Samples of Mexican-style cheeses from three different manufacturers purchased from markets in Los Angeles were cultured at CDC; four packages of Jalisco cheese products grew L. monocytogenes serotype 4b. The four positive cheese samples were of two varieties, queso fresco and cotija. All four contaminated samples had different expiration dates--ranging from June 28, to August 16, 1985--suggesting a continuing problem with this manufacturer's cheese products.

On June 13, the manufacturer instituted a voluntary recall of the implicated cheese products. Television, radio, and newspaper announcements were made warning the public against ingestion of Jalisco brand cheese products, as well as Guadalajara, Jimenez, and LaVaquita brands manufactured in the Jalisco plant. Currently, the California State Department of Food and Agriculture and the U.S. Food and Drug Administration are conducting studies of the dairy herds, physical plant, and cheese manufacturing processes.

Eighty percent of the cheese made by this manufacturer is distributed to Los Angeles and Orange Counties. However, Jalisco cheese products are distributed to at least 16 other states and most areas of California. Reported by SM James, MPH, SL Fannin, MD, BA Agee, MD, B Hall, E Parker, J Vogt, G Run, MS, J Williams, L Lieb, MPH, Los Angeles County Dept of Health Svcs, C Salminen, Los Angeles County-University of Southern California Medical Center, T Prendergast, MD, Orange County Health Dept; SB Werner, MD, J Chin, MD, State Epidemiologist, California State Dept of Health Svcs; U.S. Food and Drug Administration; Div of Field Svcs, Epidemiology Program Office, Respiratory and Special Pathogens Br, Div of Bacterial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Listeriosis is a bacterial disease causing meningitis and sepsis, especially in immunocompromised hosts. Pregnant women may also transmit the infection to their infants, resulting in abortion or early neonatal sepsis. The usual incidence of sporadic listeriosis is 2-3 per million population per year. Epidemics of listeriosis may also occur; recent outbreaks have been associated with ingestion of cabbage and pasteurized milk (1,2).

Listeriosis of the newborn may be preventable by recognition and prompt treatment of maternal listeriosis (3,4). Pregnant women who have consumed the implicated cheese and who develop fever or gastrointestinal symptoms should contact their physicians promptly. Because the cheese is distributed in at least 16 states, physicians throughout the country should consider listeriosis as a diagnosis in symptomatic, pregnant Hispanic women.


  1. Schlech WF III, Lavigne PM, Bortolussi RA, et al. Epidemic listeriosis--evidence for transmission by food. N Engl J Med 1983;308:203-6.

  2. Fleming DW, Cochi SL, MacDonald KL, et al. Pasteurized milk as a vehicle of infection in an outbreak of listeriosis. N Engl J Med 1985;312:404-7.

  3. Hume OS. Maternal Listeria monocytogenes septicemia with sparing of the fetus. Obstet Gynecol 1976;48:33s-4s.

  4. Katz VL, Weinstein L. Antepartum treatment of Listeria monocytogenes septicemia. South Med J 1982;75:1353-4.

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