Salmonella

Multistate Outbreak of Salmonella Saintpaul Infections Linked to Raw Produce

Posted July 30, 2008

Click here to go to the Final Update

This outbreak appears to be over. However, Salmonella is an important cause of human illness in the United States. More information about Salmonella, and steps people can take to reduce their risk of infection, can be found on the CDC Salmonella Web Page.

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, 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.

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 large clusters were 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. More recently, three additional large 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 fresh serrano peppers and fresh tomatoes, but not jalapeño peppers. In the third, illnesses were linked to an item that contained fresh jalapeños and tomatoes. Other clusters are still under active investigation.

It appears likely that more than one food vehicle is involved in this outbreak. It cannot all be entirely accounted for by a single food item. By themselves, tomatoes cannot explain the entire outbreak, nor do jalapeño peppers explain all the clusters. It appears likely that more than one food vehicle is involved. Although rare, more than one food has been implicated in foodborne outbreaks in the past.

At present, information indicates that jalapeño peppers 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 of Salmonella Saintpaul has been isolated twice from jalapeño peppers and once from serrano peppers.

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.

The Laboratory Services Division of the Colorado Department of Public Health and Environment detected Salmonella Saintpaul with the outbreak strain fingerprint pattern 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.

An FDA laboratory detected Salmonella Saintpaul with the outbreak strain fingerprint pattern in a sample of serrano peppers, as well as from a water sample collected on a farm in Mexico that supplied peppers to the distribution center in McAllen, Texas.

Since April, 1319 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 (3 persons), Arkansas (21), Arizona (56), California (11), Colorado (16), Connecticut (5), Florida (4), Georgia (40), Idaho (6), Illinois (116), Indiana (20), Iowa (2), Kansas (21), Kentucky (2), Louisiana (2), Maine (1), Maryland (38), Massachusetts (29), Michigan (26), Minnesota (22), Mississippi (2), Missouri (20), Montana (1), New Hampshire (5), Nevada (13), New Jersey (16), New Mexico (106), New York (39), North Carolina (28), Ohio (10), Oklahoma (25), Oregon (11), Pennsylvania (13), Rhode Island (3), South Carolina (2), Tennessee (10), Texas (502), Utah (2), Virginia (31), Vermont (2), Washington (17), 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 1281 persons with information available, illnesses began between April 10 and July 13, 2008, including 49 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 12. The latest estimated onset date is July 13. 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 255 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 between June 1 and June 7 was 35 per day. The average number of persons who became ill between June 11 and June 18 was 21 per day. The average number of persons who became ill between June 19 and July 3 was 12 per day. The outbreak appears to be ongoing, but with fewer new illnesses reported 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. Please see the Salmonella Outbreak Investigations: Timeline for Reporting Cases for more details regarding the 2-3 week time period.

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. 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.

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