How We Analyzed Death Records and Found Overdoses Rising

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Jaime Puerta (C), holds a portrait of his son Daniel Puerta-Johnson, who died in April 2020 at the age of 16 from a pill containing fentanyl, during a news conference outside the Roybal Federal Building on February 24, 2021 in Los Angeles. (Patrick T. Fallon/AFP/Getty Images)

For more than a year, reporters from KQED and the Documenting COVID-19 project have been requesting and analyzing mortality data from Bay Area counties to better understand who has died, and why.

While examining the data we realized that the increasing number of people who died in 2020 could not be explained by COVID-19 alone.

We found that since 2018, an increasing number of people had been dying as a result of drug overdoses. We identified a spike in drug overdose deaths in both 2019 and 2020 — indicating that this was not necessarily a trend born of the pandemic, but certainly one that might have been exacerbated by it.

For this report, we analyzed local mortality data from Santa Clara County Office of the Medical Examiner-Coroner, the San Francisco Office of the Chief Medical Examiner and the Alameda County Sheriff's Office Coroner’s Bureau from 2018, 2019 and 2020.

Under California law, these offices are responsible for investigating all sudden, violent and unnatural deaths, such as accidents including overdoses, suicides and homicides. Thousands more deaths that occurred at home are not part of this data set — but those deaths are represented in state data from the California Department of Public Health.


While reporting on infectious disease deaths is normally considered the purview of the medical examiner or coroner, most counties in California assigned the tracking and reporting of COVID-19-related deaths to local health departments.

In Santa Clara County, all COVID-19 deaths were reported to, and reviewed by, the Medical Examiner-Coroner’s Office, regardless of whether an individual lived in the county or elsewhere. This included deaths occurring at home, and in hospitals, long-term care facilities, nursing homes, jails and psychiatric care facilities.

County practices for testing for COVID-19 after a person dies vary widely:

  • Santa Clara County’s medical examiner performs post-mortem COVID-19 tests on decedents received by that office and suspected of having the virus.
  • Alameda County’s sheriff-coroner tests all decedents brought to the county morgue for COVID-19.
  • The San Francisco County Department of Public Health began requiring post-mortem testing of all people who died in the county since June 2020.

Also, mortality data is a snapshot in time in which there’s always a portion of cases where the cause of death is pending test results or investigation. For instance, counties withhold data if a person’s death is being investigated as a crime. During the pandemic, many agencies have also been backlogged.

How We Analyzed the Data

Santa Clara: Since December 2020, members of the Documenting COVID-19 project have filed multiple Public Records Act requests with the Santa Clara County Medical Examiner-Coroner's Office for data of all deaths in Santa Clara County between Jan. 1, 2018 through March 1, 2021.

We flagged any death records that mentioned the case-insensitive words "fentanyl" or "tox" in any field, since variations of the word "toxicity" are commonly mentioned in deaths attributed to drug overdose.

Upon plotting the counts of "fentanyl" and "tox" deaths over time, we found spikes in 2019 and the first half of 2020, but a rather anomalous drop in the second half of 2020. This drop could be due to incomplete mortality data, for instance due to cases that the medical examiner's officer is still investigating. County offices often take months to close pending cases and record the cause of death accurately.

We also found that the median age of people who died from the powerful opioid fentanyl had declined each year. Subsequently, we expanded our analysis to two neighboring counties to look for indications of a similar trend.

The unusual drop in fentanyl fatalities in the second half of 2020 was also echoed in data from Alameda and San Francisco counties. So we reached back out to the Medical Examiner-Coroner's Office in Santa Clara County to ask for a refreshed pull of death records, specifically asking for all fentanyl-related deaths and the ages of the decedents. This new records request was fulfilled on April 29, 2021. Upon plotting the raw count of fentanyl fatalities over time, we no longer saw a sharp drop off in deaths in the second half of 2020, lending us greater confidence that our data more accurately reflected the real number of people who were dying of fentanyl overdoses in Santa Clara County. We used this updated data to corroborate our previous findings about the decreasing trends in the median age of fentanyl decedents.

We found 920 COVID-related deaths in the Santa Clara County death records in 2020. A newer dataset of COVID deaths by county, compiled by California Department of Public Health, revealed that there were 932 total COVID-related deaths found in Santa Clara County. These two tallies are similar, which underscores the accuracy of fentanyl death records for 2018, 2019 and 2020 obtained from the Santa Clara County Medical Examiner-Coroner’s Office in late April 2021.

View the data on deaths in Santa Clara County from 2020, 2019 and 2018.

Alameda County: Similar to Santa Clara, the Documenting COVID-19 team received all mortality data from Jan. 1, 2018 through Feb. 27, 2020 from the Alameda County Sheriff's Office Coroner's Bureau before beginning the investigative process for this story. We realized that in order to characterize trends in the death records accurately — especially those related to fentanyl overdose — we needed to get updated data. The Alameda County Sheriff’s Office Coroner's Bureau filled our latest request on May 3, 2021. We found that the newest data showed six fewer people died of a fentanyl overdose in the second half of 2020 than previous datasets of the same time period.

View Alameda County death data.

San Francisco: Through record requests to the San Francisco Office of the Chief Medical Examiner, the Documenting COVID-19 team had previously received death records from Jan. 1, 2018 through November 2020. In March, we found that of the 1,365 total death records in this date range, 490 (35.9%) had cause of death listed as “pending” or “unknown,” indicating the Chief Medical Examiner’s Office had not closed these case investigations. However, the Accidental Overdose Reports published on the office's website showed that their office had estimated more than twice the number of people who died of a fentanyl overdose in 2020 compared to the records we were provided. We requested updated fentanyl mortality data for Jan. 1, 2018 through March 31, 2021. The Medical Examiner’s Office fulfilled our request on April 29, 2021. These latest records show 396 fentanyl fatalities in 2020. However, the office indicates in a separate report that 515 people died from a fentanyl overdose — an indication that our data, while much more complete than before, still did not reflect all the people who died of fentanyl overdoses in San Francisco. Additionally, their provided records did not show any fentanyl overdoses from January 2018 to July 2018. We are seeking further clarification on this potential data gap and have excluded this time range in our analysis.

View San Francisco County death data.

State Data:
We cross-reference our data with an analysis of California Health and Human Services’ death profiles for 2018, 2019 and 2020.

This analysis showed statewide deaths increased 30.3% (from 2018 and 2019 to 2020). The state includes data on deaths in the county where the person lived, not in the county where they died.


Kyra Senese and Eric Fan of the Documenting COVID-19 project also contributed to this report.