The article analyzes whether the recent decline in fentanyl overdose deaths in the US and Canada is related to a sudden supply shock in the illegal trade of the drug.[1] Overdose deaths from synthetic opioids in the US increased more than 25-fold over 15 years, reaching approximately 76,000 annual deaths in 2023, before declining by more than a third between mid-2023 and late 2024.[1] The authors combine data from the US and Canadian governments with an analysis of discussions on the social network Reddit to assess changes in the availability and quality of illegal fentanyl.[1] They noted a sudden decrease in fentanyl purity and availability that coincided with the decline in deaths in both countries.[1] Therefore, they conclude that there was a significant supply chain disruption that hit both the US and Canadian markets at the same time.[1] The article states that available indications point to problems in the supply of precursor chemicals from China, but the exact mechanism and extent of these measures are not clearly identifiable from open data.[1]