Food Protection Trends - September 2008 - 671

NEWS CDC Investigation of Outbreak of Infections Caused by Salmonella Saintpaul T he CDC is collaborating with public health officials in many states, and the US Food and Drug Administration (FDA) to investigate an ongoing multi-state outbreak of human Salmonella serotype Saintpaul infections. An initial epidemiologic investigation in New Mexico and Texas comparing foods eaten by persons who were ill in May to foods eaten by well persons identified consumption of raw tomatoes as strongly linked to illness. A similar but much larger nationwide study comparing persons who were ill in June to well persons found that ill persons were more likely to have recently consumed raw tomatoes, fresh jalapeño peppers, and fresh cilantro. These items were commonly, though not always, consumed together, so that study could not determine which item(s) caused the illnesses. Recently, many clusters of illnesses have been identified in several states among persons who ate at restaurants. Most clusters involve fewer than 5 ill persons. Three larger clusters have been intensively investigated. In one, illnesses were linked to consumption of an item containing fresh tomatoes and fresh jalapeño peppers. In the other two, illnesses were linked to an item containing fresh jalapeño peppers and no other of the suspect items. Other clusters are under active investigation. The accumulated data from all investigations indicate that jalapeño peppers are likely to be a major cause of this outbreak. Fresh serrano peppers and fresh tomatoes remain under investigation. Investigators from many agencies are collaborating to track the source of the implicated peppers and other produce items. An FDA laboratory detected Salmonella Saintpaul with the outbreak strain fingerprint pattern in a sample of jalapeño pepper obtained from a distribution center in McAllen, Texas. The distributor is working with FDA to recall the contaminated product in the United States. The peppers were grown in Mexico; investigators are working to determine where they were contaminated. Since April, 1,251 persons infected with Salmonella Saintpaul with the same genetic fingerprint have been identified in 43 states, the District of Columbia, and Canada. These were identified because clinical laboratories in all states send Salmonella strains from ill persons to their State public health laboratory for characterization. The outbreak can be visually described with a chart showing the number of persons who became ill each day. This chart is called an epidemic curve or epi curve. The average number of persons who became ill between May 20 and June 10 was 33 per day. The average number of persons who became ill between June 11 and June 20 was 19 per day. The outbreak appears to be ongoing, but with fewer new illnesses each day. Illnesses that occurred recently may not yet be reported due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2–3 weeks. Only 6 persons infected with this strain of Salmonella Saintpaul were identified in the country during April through June of 2007. The previous rarity of this strain and the distribution of illnesses in all US regions suggest that the implicated food is distributed throughout much of the country. Because many persons with Salmonella illness do not have a stool specimen tested, it is likely that many more illnesses have occurred than those reported. Some of these unreported illnesses may be in states that are not on today’s map. Health officials have worked continuously since late May to investigate this outbreak. CDC has sent 29 people to the field to work with other public health officials. The investigation is complex and difficult. One difficult aspect is that people often have difficulty remembering exactly what foods they ate, and remembering specific ingredients in those foods is even more difficult. Although laboratory testing of foods might help identify the source, perishable foods that were consumed by ill persons are often not available to test. When food items are mixed together and consumed in the same dish, all the items may be statistically linked to illness. In that case, determining by statistical means which item caused the illness can be difficult or impossible. Tracing suspect produce items back to processors and growers is an integral part of the effort to identify a single source and a possible means of contamination. SEPTEMBER 2008 | FOOD PROTECTION TRENDS 671

Food Protection Trends - September 2008

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