Multidrug-resistant Shigella flexneri outbreak associated with a high-mortality spillover event into nonhuman primates.

Shigellosis is a gastrointestinal infection caused by species of . A large outbreak of serotype 2a occurred in Albuquerque, New Mexico (NM) between May 2021 and November 2023 that involved humans and nonhuman primates (NHP) from a local zoo. We analyzed the genomes of 202 New Mexico isolates as well as 15 closely related isolates from other states, and four from NHP. The outbreak was initially detected within men who have sex with men (MSM) but then predominantly affected people experiencing homelessness (PEH). Nearly 70% of cases were hospitalized and there was one human death. The outbreak extended into Albuquerque's BioPark Zoo, causing high morbidity and six deaths in NHPs. The NHP isolates were identical to those in the human outbreak. All isolates were multidrug-resistant, including towards fluoroquinolones, a first line treatment option which led to treatment failures in human and NHP populations. We demonstrate the transmission of this S. strain between humans and NHPs, causing fatalities in both populations. This study demonstrates the threat of antimicrobial resistant organisms to vulnerable human and primate populations and emphasizes the value of vigilant genomic surveillance within a One Health framework.