The Food and Drug Administration has closed its investigation of an outbreak of infections from Salmonella Typhimurium that sickened more than 250 people without finding a cause for the illnesses.

The FDA first announced the outbreak on August 17, 2022. Patient numbers steadily grew, reaching 274 at the point the investigation was closed this week. 

Agency investigators conducted traceback efforts as well as sample testing and on-site inspections, but the FDA never reported what food or foods were involved in those activities. Similarly, the agency did not report what company was the subject of its on-site inspections.

As is its practice with weekly outbreak updates, the FDA did not report how old the patients were or wher they lived.

In other outbreak news, the FDA continued an investigation into a Salmonella Typhimurium outbreak traced to fresh alfalfa sprouts. The FDA is working with state and local officials as well as the federal Centers for Disease Control and Prevention on the investigation. 

According to the FDA and the CDC, the implicated sprouts are from SunSprout Enterprises in Nebraska. Some of the sprouts had expiration dates as recent as Jan. 7.

SunSprout Enterprises recalled four lots — 4211, 5211, 3212, and 4212 — of raw alfalfa sprouts in 4-ounce clamshells and 2.5-pound packages, with best-by dates between Dec. 10, 2022, and Jan. 7, 2023. An investigation is underway to determine how this alfalfa product was handled and stored after it left its Nebraska production facility, according to the FDA.

As of the most recent patient count update, which was posted by the CDC on Dec. 30, 15 people from three states have been infected. The states and the number of sick people are Nebraska with 8, South Dakota with 6, and Oklahoma with 1. Two patients have been hospitalized. No deaths have been reported.

Of 12 patients who have been interviewed so far by public health officials, all reported eating sprouts in the days before becoming sick. The patients range in age from 19 to 78 years old with a median age of 39. Sixty-seven percent of the patients are female.

Whole genome sequencing has already shown that bacteria from sick people’s samples are closely related genetically. This suggests that people in this outbreak got sick from the same food.

Additional patients will likely be identified.

“The true number of sick people in this outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because many people recover without medical care and are not tested for Salmonella. In addition, recent illnesses may not yet be reported as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak,” according to the CDC.

Anyone who has eaten sprouts and developed symptoms of Salmonella is urged to seek medical attention. It can take several days for symptoms to appear. 

Food contaminated with Salmonella bacteria does not usually look, smell, or taste spoiled. Anyone can become sick with a Salmonella infection. Infants, children, seniors, and people with weakened immune systems are at higher risk of serious illness because their immune systems are fragile, according to the CDC.

Anyone who has developed symptoms of Salmonella infection should seek medical attention. Sick people should tell their doctors about the possible exposure to Salmonella bacteria because special tests are necessary to diagnose salmonellosis. Salmonella infection symptoms can mimic other illnesses, frequently leading to misdiagnosis.

Symptoms of Salmonella infection can include diarrhea, abdominal cramps, and fever within 12 to 72 hours after eating contaminated food. Otherwise, healthy adults are usually sick for four to seven days. In some cases, however, diarrhea may be so severe that patients require hospitalization.

Older adults, children, pregnant women, and people with weakened immune systems, such as cancer patients, are more likely to develop severe illnesses and serious, sometimes life-threatening conditions.

Some people get infected without getting sick or showing any symptoms. However, they may still spread the infections to others.

In another outbreak investigation, the FDA and CDC are working to determine what brand of enoki mushrooms have sickened at least two people, one each in Nevada and Michigan.

The patients are infected with the pathogen Listeria monocytogenes and both have been hospitalized.

There have been numerous recalls of enoki mushrooms this year from a wide variety of companies and importers because of Listeria contamination.

Click on the image to enlarge it. Use the link below to go to the FDA page with links to specific outbreak information.

Additional outbreak information
Click here to go to the FDA page with links to specific outbreak details. The investigations are in a variety of stages. Some outbreaks have limited information with active investigations ongoing, others may be near completion.

A public health advisory will be issued for investigations that have resulted in specific, actionable steps for consumers to take to protect themselves, according to the FDA. Please direct your attention to those pages for the most up-to-date information on the investigation and for consumer protection information.

Outbreak and adverse event investigations that do not result in specific, actionable steps for consumers may or may not conclusively identify a source or reveal any contributing factors. Adverse event investigations rely on self-reported data. Although these reports may name a particular product, FDA will only indicate a product category in the table and will not publicly name a specific product until there is sufficient evidence to implicate that product as a cause of illnesses or adverse events. If a cause and/or contributing factors are identified that could inform future prevention, FDA commits to providing a summary of those findings.