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In 2021, the U.S. Food and Drug Administration (FDA), the Centers for Disease Control and Prevention (CDC), and state and local health and regulatory partners investigated an outbreak of Salmonella enterica serovar Oranienburg infections linked to bulb onions from Mexico, resulting in 1040 illnesses and 260 hospitalizations across 39 states, the District of Columbia, and Puerto Rico. The Kansas Department of Agriculture recovered the outbreak strain of Salmonella Oranienburg from a sample of condiment collected from an ill person's home. The condiment was made with cilantro, lime, and onions, but, at the time of collection, there were no onions remaining in it. FDA conducted traceback investigations for white, yellow, and red bulb onions, cilantro, limes, tomatoes, and jalapeño peppers. Growers in the state of Chihuahua, Mexico, were identified as supplying the implicated onions that could account for exposure to onions for all illnesses included in the traceback investigation, but investigators could not determine a single source or route of contamination. FDA collected product and environmental samples across the domestic supply chain but did not recover the outbreak strain of Salmonella. Binational collaboration and information sharing supported Mexican authorities in collecting environmental samples from two packing plants and onion, water, and environmental samples from 15 farms and firms in Chihuahua, Mexico identified through FDA's traceback investigation, but did not recover the outbreak strain.. Distributors of the implicated onions issued voluntary recalls of red, yellow, and white whole, fresh onions imported from the state of Chihuahua, Mexico. This outbreak showcased how investigators overcame significant traceback and epidemiologic challenges, the need for strengthening the ongoing collaboration between U.S. and Mexican authorities and highlighted the need for identifying practices across the supply chain that can help improve the safety of onions. • An outbreak of Salmonella Oranienburg infections was linked to onions from Mexico. • U.S. and Mexico regulatory partners collaborated on the outbreak investigation. • Traceback and epidemiologic evidence helped identify the source of the onions. • The investigation included traceback, epidemiology, and produce safety challenges. [ABSTRACT FROM AUTHOR]

Background: Nontyphoidal Salmonella causes ~1 million food-borne infections annually in the United States. We began investigating a multistate outbreak of Salmonella serotype Agona infections in April 2011., Methods: A case was defined as infection with the outbreak strain of Salmonella Agona occurring between 1 January and 25 August 2011. We developed hypotheses through iterative interviews. Product distribution analyses and traceback investigations were conducted. The Food and Drug Administration (FDA) tested papayas from Mexico for Salmonella., Results: We identified 106 case patients from 25 states. Their median age was 21 years (range, 1-91). Thirty-nine of 61 case patients (64%) reported Hispanic/Latino ethnicity; 11 of 65 (17%) travelled to Mexico before illness. Thirty-two of 56 case patients (57%) reported papaya consumption. Distribution analyses revealed that three firms, including Distributor A, distributed papaya to geographic areas that aligned with both the location and timing of illnesses. Traceback of papayas purchased by ill persons in four states identified Distributor A as the common supplier. FDA testing isolated the outbreak strain from a papaya sample collected at distributor A and from another sample collected at the US-Mexico border, destined for distributor A. FDA isolated Salmonella species from 62 of 388 papaya import samples (16%). The investigation led to a recall of fresh, whole papayas from Distributor A and an FDA import alert for all papayas from Mexico., Conclusions: This is the first reported Salmonella outbreak in the United States linked to fresh, whole papayas. The outbreak highlights important issues regarding the safety of imported produce.