The Alameda County Public Health Department, Los Angeles Department of Public Health, and California Department of Public Health (CDPH) investigated an outbreak of shigellosis associated with a Kaiser Permanente union delegate conference held at the Westin Bonaventure Hotel in downtown Los Angeles from August 21 to August 24, 2023. The event included 269 attendees from across California. This outbreak was assigned the code “OB20233135.”

A total of 32 cases were identified linked to this outbreak. Ages ranged from 41 to 71 years (median 49.5). Seventy-two percent of cases with known information were female. Known illness onset dates ranged from August 24 to August 26, 2023. Four cases were hospitalized, and no deaths were reported.

All but seven of the known cases were at least PCR positive for Shigella. At least 13 of the known cases were positive for Shigella flexneri, type 3. Whole genome sequencing determined that five of these cases were infected with near identical Shigella strains (within 0-1 alleles).

The Los Angeles Department of Public Health distributed a REDCap survey to all conference attendees to collect exposure information. A total of 85 survey responses were recorded as of September 8. The boxed lunch served on August 24, 2023 was the primary exposure of interest.The main kitchen at the Westin Bonaventure was investigated by Los Angeles County Environmental Health. The main kitchen was closed on September 1, 2023. At least one ill worker was identified with an onset of August 25, 2023. One other employee had left work early on an undetermined day. Thirteen out of 14 employees were tested: one asymptomatic employee was positive for Shigella/EIEC, EPEC who had also prepared the chicken curry and tuna salad wrap. One other asymptomatic employee was positive for STEC and did not participate in making the wrap.