Epidemic (Epi) Curves for Coronavirus COVID-19

William M. Detmer, MD, supported by the Unbound Medicine Team

Updated: Wednesday, June 03, 2020 08:55 ET

Coronavirus Guidelines

Cases and Deaths for Selected Countries

Total Confirmed COVID-19 Cases in Selected Countries
COVID-19 Case Curves in 8 Selected Countries

Total Confirmed COVID-19 Cases for eight countries (China, Iran, S. Korea, Italy, Spain, United States, UK, and Japan). Note that the left axis is logarithmic rather than linear and represents the cumulative number of cases reported to theEuropean CDC by each country.

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Data sources: European CDC. Our World in Data.[1]

Total Confirmed COVID-19 Deaths in Selected Countries
Total Confirmed Death COVID-19 in Selected Countries

Total number of deaths from COVID-19 in United States, Italy, Spain, UK, Iran, China, South Korea and Japan.

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Source: European CDC, Our World in Data.

U.S. New COVID-19 Cases by Day (CDC)
Coronavirus Epi Curve in the US

New Cases of COVID-19 in the United States by Day - through June 1, 2020. Graph shows new cases based on date of reporting.

Source: Coronavirus COVID-19 Cases in the United States. US Centers for Disease Control.[2]

U.S. Cases and Deaths by State and County
Coronavirus COVID-19 Curves by State and County

Aggregate data from the Centers for Disease Control and Prevention (CDC) and state- and local-level public health agencies. County-level data is confirmed by referencing state and local agencies directly. Confirmed cases and deaths reflect cumulative totals since January 22nd, 2020.

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Source: USAFacts.org.[3]

Projected Deaths from COVID-19 in the U.S.

Projected Deaths in the U.S. from COVID-19: May 28
Projected Deaths in the U.S. from COVID-19

Projected deaths from COVID-19 in the United States. Left: Cumulative reported COVID-19 deaths since February and forecasted deaths for the next four weeks in the United States. The CU models make various assumptions about the effectiveness of current interventions. All other models assume that existing social distancing measures will continue through the time period shown. Right: “Ensemble” forecasts summarize the information from the individual forecasts. The national ensemble forecast suggests that the rate of increase in cumulative deaths is likely to slow but still exceed 115,000 by June 20.[4]

Click to download State-Level Forecasts (PDF from CDC).

Sources: Institute for Health Metrics and Evaluation (IHME), an independent global health research center at the University of Washington,[5] Laboratory for the Modeling of Biological + Socio-technical Systems (MOBS), Columbia University (CU), Imperial College, London (Imperial), University of Geneva (Geneva), and University of Texas, Austin (UT). For other models see [4].

Global Epidemic Curve for COVID-19

Global COVID-19 Epidemic Curve (WHO)
Global Epi Curve for COVID-19 (WHO)

Epidemic curve of confirmed COVID-19 cases by WHO Region. Graph shows cases by date of case reporting through June 2, 2020.

Source: Coronavirus disease (COVID-2019) situation reports. World Health Organization.[6]

World Health Organization Regions
WHO Regions

WHO Member States are grouped into six regions. Each region has a regional office. The map shows the WHO regions and the location of the regional offices.

What is an Epidemic (Epi) Curve?

  • An epidemic curve, also known as an epi curve or epidemiological curve, is a statistical chart used to visualize the onset and progression of a disease outbreak.[7]
  • Epi curves typically display a graph of the onset of illness among cases in an outbreak.
    • Horizontal x-axis shows the date of illness onset among cases.
    • Vertical y-axis shows the number of cases.
  • For the COVID-19 outbreak, major agencies display cases differently:
    • World Health Organization (WHO) – show graphs based on the date of case reporting.[6]
    • US Centers for Disease Control (CDC) display cases by onset of illness. For COVID-19 the CDC has also started to report cumulative cases based on date of reporting.[2]

Flattening the COVID-19 Epidemic Curve

Flattening the COVID-19 Epidemic Curve
Flattening the COVID-19 Epidemic Curve

See below for explanation.

Source: US Centers for Disease Control (CDC), adapted by Unbound Medicine.

  • Without speedy and coordinated public health actions such as rapid testing, isolation of cases, "social distancing" and stay-at -home policies, the number of COVID-19 cases could rise beyond the capacity of the healthcare system to handle severe cases (see red curve in relation to healthcare system capacity line in figure above). This occurred in Wuhan, China and is happening now in parts of Italy.
  • The goal is to "flatten" the curve (green curve above) – reduce the daily rate of new cases so that the number of severe cases can be handled effectively by the healthcare system.
  • Note that public health actions taken to "flatten the curve" do not guarantee the reduction in total number of cases during a pandemic. That will be determined by additional factors such the speed by which other effective prevention measures (e.g., vaccines) are developed.

Infographics

Infographic | Flattening the Epidemic Curve
Flattening the COVID-19 Epidemic Epi Curve Infographic

Slowing the spread of the virus can reduce the chance of infection among high-risk populations and reduce the acute burden on healthcare systems and workers.

Sources: Community Mitigation Guidelines to Prevent Pandemic Influenza.[8] WHO Situation Reports.[6]

Infographic: Unbound Medicine

Tutorials

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References

  1. Total confirmed cases of COVID-19. Our World in Data. [https://ourworldindata.org…]
  2. Coronavirus Disease 2019 (COVID-19) in the U.S. United States Centers for Disease Control and Prevention. [https://www.cdc.gov…]
  3. Coronavirus Locations: COVID-19 Map by County and State. USAFacts.org. [https://usafacts.org…]

  4. COVID-19 Forecasts. U.S. Centers for Disease Control and Prevention. [https://www.cdc.gov…]
  5. United States COVID-19 Hospital Needs and Death Projections. Institute for Health Metrics and Evaluation (IHME), University of Washington, Seattle. 2020. [https://covid19.healthdata.org…]
  6. Coronavirus Disease 2019 (COVID-19) Situation Reports. World Health Organization. [https://www.who.int…]
  7. Interpretation of Epidemic (Epi) Curves during Ongoing Outbreak Investigations. US Centers for Disease Control and Prevention. [https://www.cdc.gov…]
  8. Qualls N, Levitt A, Kanade N, et al. Community Mitigation Guidelines to Prevent Pandemic Influenza - United States, 2017. MMWR Recomm Rep. 2017;66(1):1-34.  [PMID:28426646]
  9. Quick-Learn Lesson: Create an Epi Curve. US Centers for Disease Control and Prevention. [https://www.cdc.gov…]

Last updated: June 3, 2020