National Center for Health Statistics

CDC COVID-19 Mortality Surveillance 

Diba Khan1,2 and Lauren Rossen2

1Coronavirus and Other Respiratory Viruses Division, National Center for Immunization and 

Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, U.S.A.; 2

Division of Research and Methodology, National Center for Health Statistics, Centers for 

Disease Control and Prevention, Hyattsville, MD, U.S.A

“Perspectives from the COVID-19 Pandemic”

Federal Committee on Statistical Methods

October 24, 2023

Disclaimer: The findings and conclusions in this presentation are those of the author(s) and do not necessarily represent the official 

position of the Centers for Disease Control and Prevention.
Co-authors and Acknowledgements

Meeyoung Park1, Peter Grillo2,3, B. Casey Lyons7, Sarah Witter2,3, Matthew D. 

Ritchey5, Farida B. Ahmad4

, Paul Sutton4, Bob Anderson4, Jodi Cisewski4, A.D. 

McNaghten8, Adi V. Gundlapalli5

, Nikki Sigalo2, Ross Hamilton2, Amanda Jones5, 

Sylvia Murphy5 and Amitabh B. Suthar8

1Situational Awareness Team, Division of Emergency Operations, Office of Readiness and Response, 

Centers for Disease Control and Prevention, Atlanta, GA, U.S.A. 2Coronavirus and Other Respiratory 

Viruses Division, Centers for Disease Control and Prevention, Atlanta, GA, U.S.A.; 3Booz Allen Hamilton, 

McLean, Virginia, U.S.A.; 4National Center for Health Statistics, Centers for Disease Control and 

Prevention, Hyattsville, MD, U.S.A.; 5Office of Public Health Data, Surveillance, and Technology, Centers 

for Disease Control and Prevention, Atlanta, GA, U.S.A., 6Clinical Surveillance and Epidemiology Team, 

Division of Global HIV and TB, Global Health Center, Centers for Disease Control and Prevention, Atlanta, 

GA, U.S.A., 7Epidemiology and Surveillance Branch, Division of Overdose Prevention (DOP), National 

Center for Injury Prevention and Control (NCIPC), Centers for Disease Control and Prevention (CDC), 

8Division of HIV Prevention, Centers for Disease Control and Prevention, Atlanta, GA, U.S.A.
Objectives

 To describe the systems utilized by the Centers for Disease Control and 

Prevention (CDC) for tracking COVID-19-associated mortality in the United 

States using aggregate COVID-19 case and death counts (ACDC), line-level 

data stream, and National Vital Statistics System (NVSS) during and after 

expiration of Public Health Emergency (PHE), May 11, 2023.
Background

 Mortality surveillance data are instrumental in monitoring rapidly 

developing public health events such as the COVID-19 pandemic

 Mortality surveillance involves systematic death data collection for 

• analysis and interpretation

• providing critical information about the characteristics of and recent 

trends in death

• helping track life expectancy

• helping assess the impact of interventions in place to safeguard the 

public health
CDC COVID-19 Deaths Data Collection

 Three data sources were utilized by CDC to provide COVID-19 provisional 

death counts and mortality trends data for decision making and resource 

allocation.

• Individual case records

• Line-level case report data reported through the Nationally 

Notifiable Diseases Surveillance System and CSV files

• Aggregate Case and Death Counts (ACDC)

• Aggregated counts by state, county, and date of report collected via 

web-scraping, CSV submissions, and application programming 

interfaces

• The National Vital Statistics System (NVSS)

• Death certificate data
Brief history and identification of initial COVID-19 

cases and deaths

 On February 29, 2020, the first confirmed COVID-19 death was reported in 

the United States in Washington State.

 Council of State and Territorial Epidemiologists (CSTE) published their first 

interim case definition for COVID-19 associated deaths on April 5, 2020, and 

later revised the guidance definition in January 2022 and additional 

guidance was provided in November 2022

– Current definition is: “A person whose death certificate lists COVID-19 

disease or SARS-CoV-2 or an equivalent term as an underlying cause of 

death or a significant condition contributing to death”
Brief history and identification of initial COVID-19 

cases and deaths (continued)

 The National Center for Health Statistics (NCHS) provided guidance in 

March-April 2020 on certifying COVID-19—associated deaths

– To ensure consistent collection of COVID-19 information on death 

certificates, facilitate accurate ICD-10 coding, and ascertainment of 

COVID-19 deaths from death certificate data

– NCHS later expanded this guidance in February 2023 to include guidance 

for certifying deaths involving post-acute sequelae of COVID-19 (PASC or 

'long COVID')

 COVID-19 was the third leading cause of death in the United States in the 

years 2020 and 2021, and the fourth leading cause in 2022
COVID-19 Case Surveillance

 State and jurisdictional health departments voluntarily send case data to CDC 

via electronic messaging using the National Notifiable Diseases Surveillance 

System (NNDSS) or through direct CSV submissions.

 To protect individuals’ privacy, COVID-19 case data are sent to CDC without 

personal identifiers, such as names or home addresses.

 Office of Public Health Data, Surveillance, and Technology (OPHDST), National 

Center for Immunization and Respiratory Diseases (NCIRD) Surveillance 

Office, and COVID-19 Response Task Force collaborate with state, tribal, local, 

and territorial (STLT) health departments

 A national, standardized case definition is used to define confirmed and 

probable cases of SARS-CoV-2 infections classifications for cases and deaths.
Aggregate Case and Death Counts (ACDC)
ACDC

 Earlier in the pandemic, aggregate jurisdictional-level counts provided the most 

up-to-date, validated numbers on cases and deaths

 CDC worked daily with jurisdictions in a multistep process to collect data and 

confirm COVID-19 case and death numbers

– CDC collected information from official STLT websites (via web-scraping: 

automated data extraction), direct CSV submissions, and application 

programming interfaces.

– CDC performed data quality checks to identify any irregularities, make 

historical corrections, and identify jurisdictions that require further followup to align their counts.

 Collaborative processes within CDC and with jurisdictional stakeholders ensured 

the accuracy of the COVID-19 case and death numbers, which were published 

on CDC’s website.
COVID-19 Aggregate Case and Death Counts (ACDC) pipelines

Cumulative COVID-19 Death Rates per 100,000 population by 

County, January 22, 2020 – May 10, 2023*

*Cumulative COVID-19 deaths reported to CDC by county between January 22, 2020 – May 10, 2023. Data pulled May 12, 2023.
COVID-19 Situational Awareness during PHE

Aggregate Case and Death Counts (ACDC) were available through a common 

operating platform (HHS Protect) and provided essential COVID-19 data used 

to:

• describe trends and geographic patterns in COVID-19 cases and deaths;

• estimate COVID-19 community levels and disease severity;

• identify geographically localized hotspots; and

• guide national and local mitigation efforts, such as face mask wearing, 

screening and testing, and staying up-to-date with vaccinations and 

boosters
Line-level data source
Line-level data 

 Provides detailed clinical, epidemiological, and demographic data for 

more granular analyses and informs emerging scientific questions

 Include patient demographics and information:

– Age

– Race and ethnicity

– Signs and symptoms of illness

– Underlying health conditions

– Hospitalization status

– Laboratory results

– Vaccination history

– Possible routes of exposure

– Death status and date of death
How line-level data are collected

 COVID-19 is a nationally notifiable disease

 Jurisdictional health departments voluntarily transmit individual, deidentified patient case reports to CDC

– Electronic messaging to the Nationally Notifiable Diseases 

Surveillance System (NNDSS) 

– CSV files submissions into HHS Protect/DCIPHER
• Death status is available with suppression in certain public use datasets available on data.cdc.gov

• Death data from line level case surveillance is used in visualizations by demographic groups on 

COVID Data Tracker 

Deidentified data 

• Death status and death date are two of many variables 

collected about each individual COVID-19 case

• Reporting health department may be 

local/state/territorial

Identified data 

*Includes one local health jurisdiction of New York 

City.

COVID-19 Case 

Investigation 

Direct Notification 

to Health 

Department by 

Healthcare 

Providers, 

Laboratories, and 

Hospitals

Vital StatisticsDeath Certificate 

Reporting 

State/Territorial 

Public Health 

Departments Case 

Surveillance 

Database*

Line Level Public Use Datasets

COVID-19 Case

Only Epi 

Taskforce

Surveillance 

Dataset COVID Data 

Tracker 

Visualizations

Jurisdictions Centers for Disease Control and Prevention

Compile and 

Clean Data from 

All Reporting 

Jurisdictions

HL7 messaging 

or CSV

COVID-19 Line-Level Death Counts pipeline

 Takes

National Vital Statistics System (NVSS)
National Vital Statistics System

 The NVSS is the mechanism by which NCHS collects and disseminates the 

Nation’s official vital statistics on births, deaths, and fetal deaths.

– Collects, processes, and reviews death certificate data to provide the 

most complete information on causes of death

 Data are provided through contracts between NCHS and the 57 vital 

registration jurisdictions (50 States, the District of Columbia, New York 

City, and 5 territories)
 

Physician

(Cause of death 

information for 

natural causes of 

death

Medical examiner 

or coroner

(Cause of death 

information for 

external causes)

Registration of 

death certificates 

by state vital 

registration 

offices

Public Use 

Tabulated Data files 

(data.cdc.gov)

NCHS COVID-19 

Mortality 

Surveillance 

Database

NCHS COVID-19 

Data Visualizations

Jurisdictions National Vital Statistics System,

National Center for Health Statistics

Cause of death

Coding and 

review

(90% 

automatically 

coded, 10% 

manually coded)

Funeral Directors

(Complete 

demographic 

information)

Deidentified aggregated 

data updated on a daily, 

weekly, monthly, quarterly 

basis

CDC WONDER

Record-level death certificate data

Coded data 

shared with 

jurisdictions

COVID-19 National Vital Statistics System (NVSS) 
Death certificate data

Death certificate completed by:

• Funeral director (demographic 

information)

• Physician (cause of death info for 

natural causes)

• Medical examiner/coroner (cause 

of death info for injuries, deaths 

outside of a medical facility)

• After investigation (days to 

months)

Death occurs

Death 

certificate 

completed

Data sent to 

NCHS Data coded Data processed Data released

26

Jurisdictions submit data electronically, 

and ICD-10 codes are assigned to 

cause-of-death information

• ‘Fact of death’ or demographic data 

often available first

• Coding is done by automated 

software and trained DVS staff 

(‘manual coding’)

• Manual coding can take several days

• ~ 12 days currently

Data processed into several SQL 

databases, updated multiple 

times per day

• Weekly tab-delimited files 

created and archived

• Excel ‘cubes’

• Various programs to create 

data files released on the web

• Daily, weekly, monthly, 

quarterly
How long does it take for COVID-19 death certificate data to be 

complete?

Provisional data from 1/3/2021-5/22/2021, United States

NOTE: Mean percentage refers to the sum of the percentages of available death records (i.e., all causes or cause-specific death records in a given week over all cause or cause-specific death records at 52 weeks) across the 20 

reference-week units divided by the total number of reference-week units. A reference-week unit is defined as the week a set of deaths occurred. These data includes deaths that occurred in the United States and may include 

residents of U.S. territories and foreign countries.

DATA SOURCE: NCHS, National Vital Statistics System, January 3, 2021 – May 22, 2021.
NVSS Provisional COVID-19 Death Counts: 

Demographic and Geographic Detail

Causes of Death

 COVID-19

 Pneumonia and Influenza (with and 

without COVID-19)

 Other Selected Causes of Death (with 

and without COVID-19)

Demographic Detail

 Sex

 Age

 Race/Hispanic origin

 Place of death

Counts 1-9

suppressed 

28

Time Detail

 Cumulative for pandemic

 Monthly

 Weekly

Geographic Detail

 National

 HHS Region

 Jurisdiction/state

 County

 Urban/rural
COVID-19 Situational Awareness with NVSS at the end of 

PHE, May 11, 2023

Silk BJ, Scobie HM, Duck WM, et al. MMWR, 2023
NVSS: the primary leading indicator for disease severity

 Post-PHE, provisional mortality data from NVSS is the primary data source on COVID19 deaths based on date of death instead of report date

– Scobie HM, Panaggio M, Binder AM, et al.

– Observed NVSS death trends were 13 days earlier than for ACDC during Apr 1, 2022–Mar 22, 

2023

• Percentage of COVID-19 deaths is a timely disease severity indicator because 

reporting lags for COVID-19 and all-causes are similar

• While COVID-19 death counts from NVSS might be incomplete, the % of total deaths due to 

COVID-19 should be relatively unbiased

• Similar reporting lags in both the numerator and denominator

• CDC COVID Data Tracker: https://covid.cdc.gov/covid-data-tracker/#datatrackerhome
Weekly National COVID-19 Deaths, January 20th, 

2020, to May 13th, 2023*: Line-level, Aggregate Case 

and Death Counts and National Vital Statistics System. 
Weekly Trends in Provisional COVID-19 Deaths (NVSS) in the US 

Reported to CDC, Week of June 17, 2023
U.S. Percentage of Provisional Deaths Due to COVID-19 

in the Past Week, by State/Territory
Summary

 Earlier in the pandemic, ACDC provided the fastest accounting of COVID-19 mortality 

burden amongst the three systems at the national, state and county levels

 Due to advancements in vital registration systems over the course of COVID-19 

pandemic, timeliness for the NVSS and ACDC systems have become more similar 

with NVSS COVID-19 death counts at times surpassing that of line-level and 

ACDC systems

 In line-level data, key variables are incomplete (i.e. ethnicity & race combined, 

deaths (underreported), healthcare worker, pregnancy status)

 NVSS provides the most accurate and complete information on COVID-19 mortality

 NVSS suppresses counts of deaths between 1-9; data may be largely obscured at 

lower geographic levels
Summary

 Line level data contains epidemiological information about the course of infection 

and possible exposure

 Can be leveraged to guide individual, clinical, and community health actions

 With wide range of sociodemographic variables, NVSS mortality data are widely 

used to compare mortality across geographies, sex, race/ethnicities, and age groups

 As the timeliness of NVSS continues to improve, supplemental aggregate and linelevel systems will be less necessary

 Mortality data continue to be collected, processed, verified, and made public via 

COVID Data Tracker, NCHS data visualization webpages and data.cdc.gov
Conclusion

 Utilizing details from multiple surveillance systems has helped CDC to 

assess accurate, complete, and timely information on COVID-19—

associated deaths which is used to subsequently develop appropriate 

guidance to inform and safeguard the nation’s health. 
For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.

Questions?

Contact: Diba Khan ild1@cdc.gov

Thanks! Lauren Rossen
References

 Khan D, Park M, Burkholder J, et al. Tracking COVID-19 in the United States with 

surveillance of aggregate cases and deaths. Public Health Rep . Epub March 24, 

2023. https://doi.org/10.1177/00333549231163531 PMID:36960828

 Khan D, Park M, Lerma S, et al. Improving efficiency of COVID-19 aggregate case 

and death surveillance data transmission for jurisdictions: current and future role 

of application programming interfaces (APIs). J Am Med Inform Assoc. 

2022;29(10):1807-1809.

 Silk BJ, Scobie HM, Duck WM, et al. COVID-19 Surveillance After Expiration of the 

Public Health Emergency Declaration ― United States, May 11, 2023. MMWR Morb

Mortal Wkly Rep. ePub: 5 May 2023. 

DOI: http://dx.doi.org/10.15585/mmwr.mm7219e1.

 Scobie HM, Panaggio M, Binder AM, et al. Correlations and Timeliness of COVID-19 

Surveillance Data Sources and Indicators ― United States, October 1, 2020–March 

22, 2023. MMWR Morb Mortal Wkly Rep. ePub: 5 May 2023. 

DOI: http://dx.doi.org/10.15585/mmwr.mm7219e2.
References

 Khan D, et al. CDC Mortality Surveillance for the COVID-19 pandemic in the United 

States. In Journal review.
Appendix
Number of reporting jurisdictions : ACDC

 Jurisdictional level: 50 states, 5 territories (Guam, Puerto Rico, the United 

States Virgin Islands, the Commonwealth of the Northern Mariana Islands, and 

American Samoa), 3 freely associated states (FAS), New York City, and the 

District of Columbia.

 County-level: > 3,200 counties
Number of reporting jurisdictions : Line-Level

 57 jurisdictions: 50 States, the District of Columbia, New York City, and 5 US 

territories (Guam, Puerto Rico, the United States Virgin Islands, the 

Commonwealth of the Northern Mariana Islands, and American Samoa) 
Line-level COVID-19 data collection 
Guidance for Certifying COVID-19 Deaths: Key Points

 If COVID–19 played a role in the death it should 

be mentioned on the death certificate

 It is acceptable to report COVID–19 on a death 

certificate as “probable” or “presumed” –

certifiers should use their best clinical judgement 

in determining if a COVID–19 infection was likely 

and if the infection contributed to death

 Include pre-existing conditions that complicated 

death in Part 2 of the death certificate

https://www.cdc.gov/nchs/data/nvss/vsrg/vsrg03-508.pdf
National Vital Statistics System

 Final Data

– Annual Final Micro-data (record-level) files

– Analytic Reports

• Leading causes of death, life expectancy, trends, and disparities in 

mortality

– Final data available on CDC WONDER

 Provisional Data

– Tabulated counts and estimate based on incomplete data

• Quarterly Provisional Estimates

• Weekly Surveillance of Flu and Pneumonia Deaths

• Monthly Provisional Counts of Drug Overdose Deaths

– Provisional data available on CDC WONDER, updated monthly
COVID-19 Cause of Death Coding: Coding Process

 Coding systems not initially set up to code COVID-19 or to accept ICD-10 

code U07.1

 Establish coding rules

 Initially all COVID-19 records had to be manually coded

 Managing manual coding

– Prioritization

– Increase manual coding capacity

 Systems modified to automatically code some COVID-19 deaths

 Adjust coding rules

– Eventually added post-acute sequelae of COVID-19

 80-90% COVID-19 deaths automatically coded

Ahmad et al., AJPH 2021
Initial comparisons of Cumulative COVID-19 Death 

Counts by Data Source (as of 9/8/2020)

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

200000

2/1/2020 3/1/2020 4/1/2020 5/1/2020 6/1/2020 7/1/2020 8/1/2020 9/1/2020

Number of Deaths

Week ending date

NVSS New York Times

47

New York Times*, 

by date of report

NVSS, by date of 

death

*New York Times case and death data from https://github.com/nytimes/covid-19-data/blob/master/us-counties.csv, September 2020
Initial comparisons of Cumulative COVID-19 Death 

Counts by Data Source (as of 9/8/2020)

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

200000

2/1/2020 3/1/2020 4/1/2020 5/1/2020 6/1/2020 7/1/2020 8/1/2020 9/1/2020

Number of Deaths

Week ending date

NVSS New York Times 48

Because of 

reporting lags, 

recent NVSS 

counts less 

complete than 

other sources

NVSS data show that 

more deaths occurred in 

these weeks than 

initially reported
Initial comparisons between NVSS and ACDC: Cumulative COVID-19 

Death Counts in early 2020, United States

NVSS data show that more deaths 

occurred in these weeks than initially 

reported in ACDC data
Initial comparisons between NVSS and ACDC: Cumulative COVID-19 

Death Counts in early 2020, California
Initial comparisons between NVSS and ACDC: Cumulative COVID-19 

Death Counts in early 2020, Connecticut

For some 

jurisdictions with 

long reporting lags 

in NVSS, ACDC data 

were much more 

complete in recent 

weeks
Provisional NVSS COVID-19 Death Counts: Where to 

Find Them

NCHS webpages

 Coronavirus Disease (COVID-19) Death Data and Reporting Guidance

https://www.cdc.gov/nchs/nvss/covid-19.htm

– Daily Updates of Totals by Week and State

– Weekly Updates by Select Demographic and Geographic Characteristics

– Health Disparities: Race and Hispanic Origin

– Excess Deaths Associated with COVID-19

Download and API Access

 All data is simultaneously posted on data.cdc.gov

– Export in a variety of formats

– API Access - provides programmatic access to this dataset including the ability to filter, query, 

and aggregate data

 Monthly updates on CDC WONDER

52
Index of available NVSS data files

 https://www.cdc.gov/nchs/covid19/covid-19-mortality-data-files.htm
Excess deaths associated with COVID-19

https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm
What is excess mortality? The number of 

deaths

above the 

expected 

number,

for a given place 

and time period

https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm 55
Excess Deaths Directly Due to COVID-19

https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm

COVID-19

All causes 

excluding 

COVID-19

56
COVID-19

All causes 

excluding 

COVID-19

April 11, 2020

January 16, 2021

January 22, 2022

September 4, 2021 December 31, 2022

https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm
Percent of excess deaths due to COVID-19, by 

jurisdiction

February 1, 2020 –May 14, 2022

0%

20%

40%

60%

80%

100%

United States, 80%

https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm 58
Provisional COVID-19 Death Counts: Understanding 

the Numbers

Things to know about the data

 Provisional counts are not final and are subject to change

 Provisional data are not yet complete

 Death counts should not be compared across jurisdictions

Why these numbers are different

 Death certificates take time to be completed

 States report at different rates

 It takes extra time to code COVID-19 deaths

 Other reporting systems use different definitions or methods for counting deaths

https://www.cdc.gov/nchs/data/nvss/coronavirus/Understanding-COVID-19-Provisional-DeathCounts.pdf

59
Timeliness of death certificate data has been improving

Percentage of death records received within 10 days of death from 2013 to 2022

DATA SOURCE: NCHS, National Vital Statistics System, 2013-2022.