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Salmonella

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Investigation of Outbreak of Infections Caused by Salmonella Saintpaul

Cases infected with the outbreak strain of Salmonella Saintpaul, United States, by state, as of August 11, 2008, 9pm EDT

Cases infected with the outbreak strain of Salmonella Saintpaul, United States, by state, as of August 11, 2008, 9pm EDT
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Incidence of cases of infection with the outbreak strain of Salmonella Saintpaul, United States, by state, as of August 11, 2008, 9PM EDT

Incidence of cases of infection with the outbreak strain of Salmonella Saintpaul, United States, by state, as of August 11, 2008, 9PM EDT
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Interpretation of Epidemic Curves During an Active Outbreak

Interpretation of Epidemic Curves During an Active Outbreak

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Update for August 12, 2008 - Case count information as of 9 pm EDT, August 11, 2008

Click Here for Advice to Consumers

CDC is collaborating with public health officials in many states, the Indian Health Service, and the U.S. 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. This was a strong epidemiologic association, and tomatoes from that time period remain under investigation. After the public warning concerning tomatoes on June 7, cases continued to occur, though at a lower rate.

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, raw jalapeño peppers, and raw cilantro. These items were commonly, though not always, consumed together, so that study could not determine which item(s) caused the illnesses.

After the first case-control study was conducted, clusters of infection were detected that were associated with specific restaurants. Most clusters involve fewer than 5 ill persons. As of July 1, three clusters were investigated. In one, illnesses were linked to consumption of an item containing raw tomatoes and raw jalapeño peppers. In the other two, illnesses were linked to an item containing raw jalapeño peppers and no other of the suspect items. More recently, three additional clusters were investigated. Detailed investigations of these clusters indicate that jalapeño peppers do not explain all illnesses. In two of these investigations, illnesses were linked to an item containing raw serrano peppers and raw tomatoes, but not jalapeño peppers. In the third, illnesses were linked to an item that contained raw jalapeños and tomatoes. Other clusters are still under active investigation.

These epidemiological studies indicate that more than one food vehicle is involved in this outbreak. No one food item can explain the entire outbreak. Although rare, there have been outbreaks in the past in which more than one food source has been implicated.

At present, information indicates that jalapeño and serrano peppers grown, harvested, or packed in Mexico are the cause of some clusters and are major food vehicles for the outbreak. Although tomatoes currently on the market are safe, raw tomatoes consumed early in the outbreak are still under investigation. The outbreak strain Salmonella Saintpaul has been isolated twice from jalapeño peppers and once from serrano peppers. These foods were sampled as the result of traceback investigations based on the epidemiologic investigations of clusters. An FDA laboratory detected the outbreak strain Salmonella Saintpaul in a sample of a 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. An FDA laboratory detected the outbreak strain Salmonella Saintpaul in a sample of a serrano pepper and an agricultural water sample collected on a farm in Mexico that supplied peppers to the distribution center in McAllen, Texas. Results from the FDA laboratory therefore confirm that this outbreak was caused by at least two produce items, raw jalapeño and raw serrano peppers. In addition, the Laboratory Services Division of the Colorado Department of Public Health and Environment detected the outbreak strain Salmonella Saintpaul in a jalapeño pepper provided by an ill individual. The state health department is working with the FDA to determine the origin of the jalapeño pepper.

Since April,1405 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 number of ill persons identified in each state is as follows: Alabama (5 persons), Arkansas (21), Arizona (58), California (13), Colorado (17), Connecticut (5), Florida (4), Georgia (40), Idaho (6), Illinois (118), Indiana (21), Iowa (2), Kansas (21), Kentucky (2), Louisiana (3), Maine (1), Maryland (39), Massachusetts (30), Michigan (26), Minnesota (22), Mississippi (2), Missouri (20), Montana (1), New Hampshire (5), Nevada (14), New Jersey (16), New Mexico (110), New York (41), North Carolina (28), Ohio (10), Oklahoma (38), Oregon (11), Pennsylvania (13), Rhode Island (3), South Carolina (2), Tennessee (10), Texas (554), Utah (2), Virginia (31), Vermont (2), Washington (18), West Virginia (1), Wisconsin (13), and the District of Columbia (1). Five ill persons are reported from Canada. Four appear to have been infected while traveling in the United States; the travel status of the fifth ill person is unknown.

Among the 1368 persons with information available, illnesses began between April 10 and July 26, 2008, including 86 who became ill on July 1 or later. These numbers include those with estimated onset dates as well as those with reported onset dates. The latest reported onset date is July 24. The latest estimated onset date is July 26. Patients range in age from <1 to 99 years; 50% are female. The rate of illness is highest among persons 20 to 29 years old; the rate of illness is lowest in children 10 to 19 years old and in persons 80 or more years old. At least 272 persons were hospitalized. A man in his eighties who died in Texas from cardiopulmonary failure had an infection with the outbreak strain at the time of his death; the infection may have contributed to his death. A man in his sixties who died in Texas from cancer had an infection with the outbreak strain of at the time of his death; the infection may have contributed to his death.

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. Please see Interpretation of Epidemic Curves During an Active Outbreak. It shows that the number of persons who became ill peaked during May and decreased in June. The average number of persons who became ill in recent weeks continues to decrease, indicating that the outbreak is ending. The average number of persons who became ill each day between May 21 and June 1 was 38, between June 2 and June 12 was 34, between June 13 and 23 was 21, between June 23 and July 4 was 11, and between July 5 and July 15 was 3. More recent illnesses may not yet be reported because it takes an average of 2-3 weeks. between when a person becomes ill and when the illness is reported. (see the Salmonella Outbreak Investigations: Timeline for Reporting Cases).

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 U.S. 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. The CDC call center was utilized with >200 additional staff, and CDC has sent 39 people to the field, which includes seven Epi-Aid investigations, to work with other public health officials. The overall Salmonella Saintpaul outbreak 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.

Clinical features of Salmonella Infection

Most persons infected with Salmonella develop diarrhea, fever, and abdominal cramps 12-72 hours after infection. Infection is usually diagnosed by culture of a stool sample. The illness usually lasts 4-7 days. Although most people recover without treatment, severe infections may occur. Infants, elderly persons, and those with impaired immune systems are more likely than others to develop severe illness. When severe infection occurs, Salmonella may spread from the intestines to the bloodstream and then to other body sites, and can cause death. In these severe cases, antibiotic treatment may be necessary.

Advice to consumers

FDA is advising consumers that they should avoid raw jalapeño peppers and raw serrano peppers and foods that contain them, if they were grown, harvested, or packed in Mexico. Jalapeño and serrano peppers grown in the United States are not connected with this outbreak. Commercially canned, pickled, and cooked jalapeño peppers are also not connected with the outbreak.

This new advisory is based on evidence gathered during a multi-week, intensive investigation conducted in partnership with FDA and several states to find the source of the contamination which led to the outbreak.

FDA has indicated that tomatoes on the market today are safe to consume.

Consumers everywhere are advised to follow the general food safety guidelines below:

  • Refrigerate within 2 hours or discard cut, peeled, or cooked produce items
  • Avoid purchasing bruised or damaged produce items, and discard any that appear spoiled.
  • Thoroughly wash all produce items under running water.
  • Keep produce items that will be consumed raw separate from raw meats, raw seafood, and raw produce items.
  • Wash cutting boards, dishes, utensils, and counter tops with hot water and soap when switching between types of food products.

Consumers are reminded that vegetables are an important part of a healthy diet and that cooking vegetables kills bacteria, including Salmonella.

FDA information on this investigation can be found at: http://www.fda.gov/oc/opacom/hottopics/tomatoes.html*

More information about Salmonella and this investigation can be found at:

Information on the safe handling of produce can be found at: www.cfsan.fda.gov/~dms/prodsafe.html.*

Previous Updates on this Outbreak

* Links to non-Federal organizations found at this site are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization Web pages found at these links.

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NOTICE: The information on this page is no longer being updated and may have changed. The information is accurate only as of the last page update.

Page last modified: August 12, 2008
Content Source: National Center for Zoonotic, Vector-Borne, and Enteric Diseases (ZVED)