The Victim Count Nears 1500, with over 200 Hospitalizations in the Red Onion Salmonella Outbreak – Heath Investigators in Two Countries Scramble to Get it Under Control
The CDC has released new information on the Salmonella red onion outbreak, which has caused 1012 illnesses in the United States, with illnesses in 47 states and 136 infections requiring hospitalizations. In Canada, there have been 457 confirmed cases and 66 individuals requiring hospitalizations with illnesses in the following provinces: British Columbia (107), Alberta (257), Saskatchewan (33), Manitoba (25), Ontario (11), Quebec (23) and Prince Edward Island (1). There has also been one reported death, though officials have not confirmed if the Salmonella infection is the official cause of death, nor if it contributed to it. The CDC has been conducting an epidemiological traceback investigation to determine the cause and source of infection for the outbreak. This has included interviewing victims of the outbreak and analyzing samples taken from each victim.
Whole genome sequencing (WGS) is the method by which investigators obtain a DNA “fingerprint” of an organism, including Salmonella bacteria. By utilizing WGS, the CDC was able to connect the Salmonella outbreak in Canada and in the United States to Thomson International, Inc., red onions. After testing bacteria samples from 732 outbreak victims, scientists found that the Salmonella infections caused by the red onions were also unlikely to be antibiotic resistant.
Through traceback technology, the CDC determined that red onions are the most likely source of the outbreak, though it was necessary to recall all types of onions from Thomson International, Inc., due to concerns of cross contamination. While interviewing victims of the outbreak, 90% reported consuming onions a week before experiencing food poisoning symptoms, with 67% reporting eating red onions, 62% eating white onions, and 56% eating yellow onions, though most reported eating more than one type of onion. In 13 states, 34 illness clusters have been identified, meaning groups of infected people in different households that have reported eating onions from the same source, such as from the same restaurants or purchasing them from the same grocery store. Of these 34 illness clusters, 23 were investigated. All connected restaurants and grocery stores of the 23 illness clusters reported serving/ selling onions, and of the 23 illness clusters, seventeen (74%) served red onions, 13 (57%) served yellow onions, and 10 (43%) served white onions. Several of the onions served and purchased by the illness clusters were then traced back to producer Thomson International, Inc.
Although the cause of contamination is still not fully known with investigations remaining ongoing, the CDC has been able to connect victims of the outbreak to Thomson International, Inc., red onions through their WGS and epidemiological traceback investigation.