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Published in final edited form as: Drug Alcohol Depend. 2025 Jul 7;274:112784. doi: 10.1016/j.drugalcdep.2025.112784

Another Carfentanil Fatal Outbreak in Florida?

Chris Delcher 1, Eugene Shin 1, Arjun Iyer 2, Trokon K Johnson 2, Agnes D Winokur 3, Bruce A Goldberger 2
PMCID: PMC12287913  NIHMSID: NIHMS2097674  PMID: 40675009

Abstract

Background

In 2016 and 2017, carfentanil was implicated in the deadliest fatal outbreak involving a fentanyl analog in the United States with 1,190 deaths in Florida alone. Recent surveillance signals suggest that Florida is experiencing a resurgence in carfentanil-involved deaths. The purpose of this paper is to examine carfentanil-involved overdoses using up-to-date medical examiners reports triangulated with carfentanil-related indicators at multiple levels.

Methods

Florida’s medical examiner data were analyzed in three periods (2016, 2017, 2018–2023) to examine changes in decedent demographic, geographic, and toxicologic characteristics. We triangulated six additional state and national data sources which included completed death certificates, the National Forensic Laboratory Information System, Reddit mentions, and clinical urine drug tests positive for carfentanil.

Results

There were 24 carfentanil-involved deaths in a 2-month period (Dec/Nov 2023). Compared to 2017, recent decedents were significantly older (42.9 years old vs. 37.1 years old, p<0.0001) with increased exposure to fentanyl (23.4% to 68.8%, p<.0001) and methamphetamine (8.5% to 20.4%, p=0.0003). The state’s prior three-county epicenter showed limited involvement (6.5% vs. 18.9% total carfentanil deaths) when compared to the prior outbreak. All triangulated national data sources showed strong retrospective concordance. More timely death certificate data suggests that monthly carfentanil deaths were more frequent (mean=4 deaths/mo.) in 2024.

Conclusions

The state may have averted a fatal outbreak as of December 2024, but carfentanil deaths have reached new monthly levels with increasingly active signals in other systems. These systems should be monitored regularly to decrease lag time in fatal overdose surveillance for a faster public health response.

Keywords: Carfentanil, fatal overdoses, Florida, surveillance

1. Introduction

Carfentanil, a synthetic opioid 100 times more potent than fentanyl and used to tranquilize large animals, was implicated in an outbreak of fatal overdoses in the United States that began in June 2016 and largely subsided by the end of 2019(Delcher et al., 2020; O’Donnell et al., 2018). Due to its severity, the two-year period of increasing fatal overdoses was characterized as “hyper-exponential” even against the background of an already exponential polysubstance drug crisis(Jalal et al., 2018; Jalal and Burke, 2020). According to the Centers for Disease Control and Prevention (CDC), 10 states reported 1,236 carfentanil deaths from July 2016 to June 2017and some of those states reported fatalities well into 2018 and 2019 (Bhullar et al., 2022; Noriega et al., 2023). The CDC’s analysis did not include decedents from Florida, the state recognized as one of the epicenters, accounting for 1,181 deaths (41% of all U.S. carfentanil fatal overdoses during that period)(Delcher et al., 2020; O’Donnell et al., 2018). Ultimately, the CDC moved to enhance overdose surveillance for carfentanil and other substances via the State Unintentional Drug Overdose Reporting System (SUDORS) but Florida data is unavailable publicly(“SUDORS Dashboard,” 2022).

A concerning report from the CDC indicated that from January 2021 to June 2024, there were 513 fatal overdoses involving carfentanil with a precipitous increase (503%) towards the end of 2023 and geographic expansion from 10 to 37 states(Tanz et al., 2024). In that report, Florida was one of the states most impacted with >20 deaths reported from January 2023 to June 2024(Tanz et al., 2024). However, no demographic details, epidemiologic comparisons to the prior outbreak period, or triangulation to other relevant data sources were provided.

Given Florida’s history with carfentanil and new questions raised about the drug’s potential re-emergence after an extended period of abatement, we examined the epidemiologic and toxicological characteristics of fatal overdoses reported by the Florida Department of Law Enforcement’s Medical Examiners Commission (MEC) from January 2016 to December 2023 (96 months). Further, we use a framework of epidemiologic data triangulation(Joint United Nations Programme on HIV/AIDS, 2010) with data sources correlated with drug supply, population exposure, and fatal overdoses to enhance the contextual analysis and local surveillance of carfentanil.

2. Methods

Florida’s medical examiners report drug-related deaths to the MEC with case details including cause and manner of death, demographics, and toxicology findings(Chatterton et al., 2020). Reports of specific drugs in deceased persons are published by the MEC. Carfentanil and other fentanyl analog reports were required beginning January 2016 and xylazine in January 2022. A substance was co-occurring if it was toxicologically detected irrespective of whether the medical examiner determined that it caused the fatal overdose. For this analysis, we report deaths as “carfentanil-involved” since causal determination is inconsistently reported for this drug. We examined geography by tabulating fatal overdoses in 1) each of Florida’s 67 counties, 2) Florida’s High Intensity Drug Trafficking Areas (HIDTA)(U.S. Drug Enforcement Administration, 2023) and 3) the Sarasota area (Sarasota, Manatee, and DeSoto counties, prior epicenter).(Delcher et al., 2020)

To examine demographic changes through time, we primarily compared 2017 to the aggregate six-year period January 2018 to December 2023 (post-outbreak period). The aggregation was required to increase sample size. We calculated the percentage of all opioid-involved deaths attributable to carfentanil. Descriptive statistics with distribution tests (Chi-square or Fisher’s exact for categorical, t-tests for numeric, with statistical significance defined as p<0.05) and epidemic curve analysis were conducted using SAS (version 9.4; SAS Institute).

Data triangulation

We triangulated data sources described below by plotting counts/rates at the highest temporal resolution available from January 2016 to December 2024. These state and/or national data sources were largely unavailable during the first carfentanil outbreak investigation (January 2016 to December 2017)(Delcher et al., 2020).

Vital Statistics (Florida)

We examined monthly counts of drug-related deaths from January 2016 to December 2024 from the Florida Department of Health. International Classification of Diseases (ICD) codes X40-X44, X60-X64, Y10-Y14) combined with text mentions for “carfentanil” in the cause-of-death (COD) and descriptions of how injury occurred fields were used. Demographic information for comparison to MEC data was unavailable to the authors.

National Forensic Laboratory Information System (NFLIS)(Florida)

The number of law enforcement samples testing positive for carfentanil from participating crime laboratories in Florida from 2016 to 2024 in 6-month periods are available from the U.S. Drug Enforcement Administration’s NFLIS public data query system (Drug Enforcement Administration, 2025a; Pitts et al., 2023). Details on the chemical analysis of carfentanil samples was provided by the U.S. Drug Enforcement Administration.

Social media posts (national)

From personal communication, we obtained the standardized, monthly rate of the mentions of carfentanil from national substance use forums on Reddit from January 2010 to December 2017(Bowen et al., 2019). This series represents the frequency of posts with the word carfentanil per 100,000 posts to these forums.

Clinical Urine Drug Tests (UDT) (national)

We obtained national-level, monthly UDTs positive for carfentanil, among fentanyl and/or norfentanyl positive specimens, from August 2019 (first testing month) to December 2024 from Millennium Health™ (San Diego, CA)(“Carfentanil Signals Alert | Millennium Health,” 2024). The national, monthly carfentanil positivity rate was calculated as the number of tests with a positive result for carfentanil divided by the total number of specimens tested. Data was provided in February 2025.

The study was exempt from review by the University of Florida and University of Kentucky institutional review boards. The data obtained and analyzed by the investigators were de-identified and are publicly available.

3. Results

From January 2018 to December 2023, there were 93 carfentanil-involved fatal overdoses in Florida with 24 (25.8%) deaths in November and December 2023 alone. Compared to the 637 deaths in 2017 (the apex of the prior outbreak), the mean age was significantly older (42.9 years old vs. 37.1 years old, p<0.0001). The percentages of females (26.9% vs. 23.9%, n.s.) and non-White (15.1% vs. 9.6%, n.s.) decedents were slightly higher in the 2018–2023 period but differences were not significant. In terms of the polysubstance composition of carfentanil-involved deaths, the percentage containing the fentanyl parent increased substantially (23.4% to 68.8%, p <0.0001) as did the percentage of deaths involving methamphetamine (8.5% to 20.4%, p=0.0003). Fluorofentanyl composition increased significantly to 8.6% (p<0.0001) from 2 to 8 cases though numbers are small. Xylazine was present in 8 of 36 carfentanil deaths (22%) all of which occurred in the last 3 months of 2023. Xylazine-involved overdoses increased by 16.7% between 2022 and 2023 (472 to 551 deaths, respectively) in Florida.

Over the entire 8-year study period (2016 to 2023), 41 of 67 counties in Florida reported ≥1 carfentanil death. Twenty of those counties reported no carfentanil deaths after the initial outbreak subsided, but four counties (Franklin, Hernando, Okeechobee, and Washington) reported their first deaths (each with one death) from carfentanil after 2018. In 2017, the South Florida HIDTA accounted for 62% of all carfentanil deaths statewide which increased to 68%. Approximately 14% of carfentanil deaths occurred in non-HIDTA counties including the four counties above.

The Sarasota area accounted for 18.9% of the carfentanil deaths (n=225) in the prior outbreak compared to 6.5% (n=6) in the 2018–2023 period. Palm Beach County had the highest carfentanil mortality rate (19.4 per 100,000) in 2017.(Delcher et al., 2020) Similarly, Palm Beach County accounted for 46% of carfentanil-involved deaths in the 2018–2023 period(n=43). Lee County (Fort Myers area), geographically connected to the Sarasota area via large waterways, accounted for 10.7% of the carfentanil deaths (n=10). Lee County joined the South Florida HIDTA in 2023.(Office of National Drug Control Policy, 2025)

During the peak month of October 2016, carfentanil accounted for 36% (165 deaths) of all opioid-involved deaths (454 deaths) in Florida (Figure 1). Since 2018, carfentanil deaths were rare; never accounting for more than 5% of monthly opioid deaths. In November 2019, four carfentanil deaths (0.9% of all opioid deaths, n=408) were reported but subsequently subsided. Suddenly in October 2023, there were 8 carfentanil involved deaths, the highest in a ~67 month period. There was a subsequent increase to 12 deaths reported in both November and December 2023 (most recent data from the MEC). To extend our mortality surveillance window to December 2024 given the lag in MEC data, we triangulated vital statistics which showed another 10 deaths in January 2024, a surge that dissipated inconsistently by the end of 2024. A total of 56 carfentanil deaths occurred in 2024 (mean=4 deaths per month). One of these deaths was adjudicated as “fetal demise” due to maternal drug use.

Figure 1.

Figure 1.

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Panel A. Opioid-caused (n=39,913) fatal overdoses, carfentanil-involved (n=1,283) fatal overdoses, and the percentage attributed to carfentanil (secondary axis), January 2016 to December 2023 (most recent), Florida (Source: Florida Department of Law Enforcement, Medical Examiners Commission). Panel B. Carfentanil-involved fatal overdoses identified from text in cause of death fields (n=1,150 deaths), (Source: Florida Vital Statistics). Panel C. Submissions to the National Forensic Laboratory Information System (NFLIS) positive for carfentanil. Panel D. Carfentanil positive specimens from clinical UDTs positive for fentanyl, August 2019 to December 2024, United States. (Source: Millennium Health™). Panel E. Carfentanil mentions among substance use discussions on Reddit, January 2016 to January 2018 (last available), United States. Source: Bowen et al. (2019). Study years are banded with reference lines showing Florida’s carfentanil outbreak in 2016 and 2017 and the start of the COVID-19 emergency.

The total number of clinical specimens tested for carfentanil was 238,073 with a monthly mean of 3,553 specimens (range: 1,529–5,040). Carfentanil-positive UDTs peaked at 3.5% in October 2019 and remained below 0.05% for several years until a steady increase began in late 2023. Positivity surpassed 1% in October 2024.

Carfentanil was reported in 813 NFLIS submissions in Florida from 2016–2022, with no reports in 2022, before increasing again in 2023 (n=6) and 2024 (n=24, the highest since 2018). During the prior outbreak, the majority of carfentanil taken into custody by the DEA originated from the West Palm Beach and Tampa areas, 16% and 12%, respectively. Heroin was the suspected drug in most carfentanil samples, but was only confirmed to be present in <8% of samples, and diphenhydramine (e.g., Benadryl) was found in ~14% of samples. More recently (2024), 75% of the carfentanil samples taken into custody were from Escambia County (Pensacola area). One of the 12 statewide carfentanil deaths in December 2023 occurred in Escambia County. In 2024, four carfentanil positive seized drug samples from Florida, analyzed by the DEA, contained fentanyl, and other substances like methamphetamine, cocaine, tramadol, and p-fluorofentanyl.

Limitations

We employed a more sensitive text identification tool in the current analysis and identified nine carfentanil-involved deaths not attributed to the first outbreak, but our prior statistical findings remained the same. Our 2018–2023 sample size was relatively small, despite temporal aggregation, so quantitative measures should be interpreted with caution. The 2024 vital statistics data is considered provisional and subject to change.

4. Discussion

In 2023, carfentanil-involved deaths in Florida suddenly returned to levels unobserved since the state’s last fatal outbreak ended in 2017. Decedents were several years older on average than those previously reported. The findings of increasing co-occurrence of fentanyl, methamphetamine, and fluorofentanyl are consistent with carfentanil deaths in the U.S. and other local studies of illicitly manufactured fentanyl (IMF)(Tanz et al., 2024; Trecki et al., 2022; Truver et al., 2022). Though maternal use of carfentanil has been reported(Griffiths et al., 2021),we identified the first carfentanil-attributed fetal death. Further, we identified the co-occurring mixture of xylazine and carfentanil in Florida’s drug decedents for the first time.

The urgency to determine whether Florida is experiencing a new outbreak required structural data triangulation. One of the limitations of medical examiner data, with few exceptions in the U.S., is the time lag to public dissemination (~18 months)(Delcher et al., 2022; Slavova et al., 2019). For our study, we looked beyond the MEC time frame at more timely counts from vital statistics. As expected, that data strongly followed the long-term epidemiologic curves generated from the MEC data (though vital statistics data may underestimate the absolute number of carfentanil fatalities). Triangulating these two data sources, we determined that carfentanil deaths likely dissipated by December 2024.

Even so, carfentanil’s potency, approximately 100 times that of fentanyl(Delcher et al., 2020), means that fatal outbreaks can start small and escalate rapidly(Rodda, 2024). In Florida, the first outbreak began with just 5 carfentanil deaths (June 2016); a 10-fold increase occurred just one month later (54 deaths), followed by 165 deaths four months later(Delcher et al., 2020). On average, the carfentanil deaths in 2024, while below prior epidemic threshold, have increased to concerning new levels. Thus, even though fentanyl deaths overall are declining precipitously in the U.S.(Garnett et al., 2024), authorities should remain vigilant with deaths involving fentanyl analogs and other synthetic drugs even when just a few local cases are reported. According to the DEA, over 100,000 fake oxycodone pills containing carfentanil were seized in the Los Angeles, CA area in February 2025.(Drug Enforcement Administration, 2025b)

By examining 96 months of surveillance data, we also found that the temporal dynamics of the carfentanil-involved mortality may deviate from the overarching fentanyl-driven opioid epidemic. For example, the deadliest month in the history of Florida’s opioid epidemic was May 2020 with 668 opioid-involved deaths, 598 attributable to fentanyl, yet only 1 carfentanil death occurred that month (see Figure 1). In fact, we found that an important feature of the relationship between fentanyl and carfentanil deaths in Florida is that carfentanil may emerge in periods of lower fentanyl mortality. For example, there were eight carfentanil deaths in October 2023which corresponded to the lowest number of fentanyl-caused deaths observed since the beginning of the COVID-19 pandemic (Figure 1).

Market prices for IMF appear to be declining (depending on geographic region) along with purity which could drive demand for more potent alternatives including analogs like carfentanil(Drug Enforcement Administration, 2025b; Kilmer et al., 2022). This might be akin to the substitution to heroin and oxymorphone that occurred immediately after OxyContin® was reformulated to a less “potent” abuse-deterrent product(Delcher et al., 2024). Early in the U.S. opioid epidemic, a similar dynamic was observed when heroin purity declined and deaths from fentanyl increased(Hempstead and Yildirim, 2014). Also, we found a rising prevalence of methamphetamine in carfentanil overdoses which may reflect an increasingly volatile stimulant market.(Wagner et al., 2023)

Beginning in 2018, there was an extended period of quiescence from carfentanil in Florida that we corroborated by triangulating multiple data sources. Carfentanil disappeared so abruptly from national UDTs early in the pandemic that it was described as a “collapse”(The COVID-19 Connection: Millennium Health Signals Report, 2021). This rapid and sustained dissipation may be associated with responses at multiple levels.. For example, from February 2017 to March 2018, China announced export controls on carfentanil, the United Nation’s placed controls on precursors to the production of IMF(United Nations, 2017; U.S. Drug Enforcement Administration, Diversion Control Division, 2017) and carfentanil was scheduled internationally(United Nations, 2018). These regulatory actions coincide with the end of the outbreak in Florida and other jurisdictions, but it is unclear if the carfentanil supply was equally disrupted in all markets. For example, in Cuyahoga County, Ohio (another prior epicenter), carfentanil deaths rose unexpectedly and peaked at 80 deaths in late 2019(Jalal and Burke, 2020; Noriega, 2023). We also recognize state/local efforts to deploy naloxone around this time. From Q2 2016 (Apr-Jun) to Q3 2016 (Jul-Sep) naloxone use increased by 30% in Florida, one of the largest increases on record from 2015 to 2024(“FLHealthCHARTS.gov,” 2025).

This extended period of quiescence was interrupted periodically. For example, four carfentanil-involved deaths were reported in November 2019, an increase that was correlated with distinct spikes in published reports of carfentanil positive NFLIS submissions in the state(Cano et al., 2023). This was consistent with research demonstrating a strong correlation between NFLIS fentanyl submissions and opioid-involved overdoses(Zibbell et al., 2023). National carfentanil positive UDTs also peaked in October 2019 at 3.4%, abating by the end of the COVID-19 emergency period. Though three triangulated data sources “alerted”, that temporary spike in carfentanil deaths never materialized into an outbreak in Florida as the COVID-19 pandemic hit.

During the prior outbreak, carfentanil mentions on Reddit increased from approximately 1 post per 100,000 to 13 posts per 100,000 posts on substance use message boards from 2015 to 2016, respectively(Bowen et al., 2019). When we examined monthly posts obtained directly from the authors, remarkably, we found the increase started in June 2016; precisely aligned with the beginning of the outbreak (Figure 1). In June 2024, Reddit users reportedly began posting concerns of a carfentanil resurgence. (Dunn et al., 2025). Simultaneously, UDTs in Florida have been increasing. Carfentanil was reported from a U.S. community drug-checking program for the first time in March 2024 and as recently as June 2025.

5. Conclusions

Carfentanil has clearly reemerged in the illicit drug supply in Florida and the U.S. even in the broader context of declining fentanyl mortality(Vasan, 2024). Evidence of a new state-level outbreak is inconclusive but monthly deaths from carfentanil have reached concerning new levels and signals from other systems were active in late 2024 into 2025. Florida’s fatal drug trends are structurally correlated with these other state and national level systems so public health authorities should closely monitor these external data sources alongside fentanyl analog overdoses in the state.

Table 1.

Characteristics of carfentanil-involved overdose deaths — Florida, 2016, 2017 and 2018–2023.

2016 2017 2018–2023 All
No. % No. % p No. % p N
Age group (yrs)
< 25 58 10.5 74 11.6 0.9085 4 4.3 0.0006 136
25–34 210 38.0 241 37.8 22 23.7 473
35–44 141 25.5 155 24.3 25 26.9 321
45–54 84 15.2 104 16.3 24 25.8 212
>=55 60 10.8 63 9.9 18 19.4 141
Age (yrs, mean) 37.5 37 0.5455 42.9 <.0001
Sex
Female 117 21.2 152 23.9 0.2659 25 26.9 0.5256 294
Male 436 78.8 485 76.1 68 73.1 989
Race
White 501 90.6 576 90.4 0.9192 79 84.9 0.1041 1,156
Other 52 9.4 61 9.6 14 15.1 127
Manner of Death
Accident 548 99.1 627 98.4 0.4359 89 95.7 0.0904 1,264
Other 5 0.9 10 1.6 4 4.3 19
Co-occurring
Drugs
Opioids
Fentanyl 107 19.3 149 23.4 0.0906 64 68.8 <.0001 320
Heroin 111 20.1 147 23.1 0.2097 21 22.6 0.9154 279
Methadone 23 4.2 20 3.1 0.3473 4 4.3 0.5323 47
Morphine 182 32.9 207 32.5 0.8789 32 34.4 0.7135 421
Oxycodone 56 10.1 48 7.5 0.1144 7 7.5 0.9977 111
Tramadol 30 5.4 14 2.2 0.0033 3 3.2 0.4669 47
Fluorofentanyl 11 2.0 2 0.3 0.0089 8 8.6 <.0001 21
Buprenorphine 14 2.5 21 3.3 0.4359 4 4.3 0.5463 39
Other
Cocaine 283 51.2 277 43.5 0.008 43 46.2 0.6174 603
Methamphetamine 43 7.8 54 8.5 0.6592 19 20.4 0.0003 116
Alprazolam 111 20.1 146 22.9 0.2338 27 29.0 0.1954 284
Ketamine 3 0.5 0 0.0 0.1001 2 2.2 0.0161 5
Prior epicenter
Sarasota 114 20.6 111 17.4 0.1611 6 6.5 0.0070 231
HIDTA (2023)
Non-HIDTA 33 6.0 67 10.5 0.0207 13 14.0 0.0856 113
Central Florida 116 21.0 117 18.4 9 9.7 242
North Florida 31 5.6 26 4.1 7 7.5 64
South Florida 373 67.5 427 67.0 64 68.8 864
All 553 100 637 100 93 100 1,283
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Bolded p-values indicates minimum significance at p =0.10. Fisher’s exact test was used for testing when cell counts were <=5. p-values indicates period testing between (2017 and 2016) or (2018–2023 and 2017)

HIDTA=High Intensity Drug Trafficking Area https://www.hidtaprogram.org/

Other manners of death can include homicide, natural, suicide, and undetermined.

Highlights.

  • In Florida, carfentanil-involved overdose deaths resurged in 2023

  • Recent decedents had increased exposure to fentanyl, methamphetamine, and fluorofentanyl

  • Xylazine and carfentanil were detected together in fatal overdoses for the first time in Florida

  • Carfentanil signals from multiple systems fit the epidemic curve of fatal overdoses

  • Carfentanil still poses a public health concern even as fentanyl deaths decline in the U.S.

Acknowledgments:

The authors acknowledge Whitney Van Arsdale (Florida Department of Health), Daniel A. Bowen (Reddit posts), and Rasaq Oladapo for data assistance. We would also like to thank Millennium Health, LLC for contributing the clinical urine drug testing data as well as Drs. Levi Bolin and Steven Passik at Millennium Health for their insights on these data and helpful comments on the manuscript.

Funding:

Funding provided by the National Institutes of Health - National Institute on Drug Abuse Award U01DA051126; and the South Florida High Intensity Drug Trafficking Areas (HIDTA).

Footnotes

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Declaration of Interest Statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Conflicts of Interest: The authors declare no potential conflicts of interest.

MEC data availability

Publicly available data on fatal drug overdoses in Florida and county/HIDTA maps are available from the University of Florida’s Florida drug-Related Outcomes and Surveillance Tracking (FROST) dashboard at https://frost.med.ufl.edu/.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

Publicly available data on fatal drug overdoses in Florida and county/HIDTA maps are available from the University of Florida’s Florida drug-Related Outcomes and Surveillance Tracking (FROST) dashboard at https://frost.med.ufl.edu/.

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