A medium throughput approach for single cell copy number variation sequencing towards efficient application in clinics.

Fatal overdoses involving opioids have increased in the US since 1999, with recent decreases beginning in 2023 (; ). Trends in types of opioids involved in fatal overdoses have shifted over time (; Centers for Disease Control and Prevention, 2024). Heroin-involved overdose age-adjusted mortality rates increased from 2002 to 2016, stabilized from 2016 to 2020, then decreased from 2020 to 2023 (). In contrast, rates involving synthetic opioids (e.g. fentanyl) were stable from 2002 to 2013, increased through 2022, and declined in 2023 (). Recent national trends in rates of nonfatal overdoses by opioid type, specifically heroin and fentanyl, are less described in the literature. One study found, while opioid-involved nonfatal overdoses increased overall from 2010 to 2020, those involving heroin decreased from 2016 to 2020 (). However, only one study has looked specifically at fentanyl-involved overdose trends through September 2021 (). Given the rapidly-evolving drug overdose epidemic, more recent data are needed to understand the current trends in nonfatal opioid-involved overdoses to inform overdose prevention and response strategies. Syndromic surveillance data have been used to examine near realtime trends in nonfatal opioid-involved overdoses treated in emergency departments (EDs) (; ). This data source uses chief complaint text and standardized discharge diagnosis codes (e.g., International Classification of Diseases, 10th revision, Clinical Modification (ICD-10-CM)) to identify suspected nonfatal overdose-related ED visits. In October 2020, a new ICD-10-CM code was introduced for fentanyl poisoning (T40.41). Shortly thereafter, the Centers for Disease Control and Prevention (CDC) developed a new syndrome definition () incorporating discharge diagnosis (including T40.41) and chief complaint to capture fentanyl-involved overdoses (; ). These developments provide an opportunity to examine recent trends in the types of opioids (e.g., fentanyl, heroin) involved in nonfatal opioid overdoses.