Epidemic (Epi) Curves for Coronavirus COVID-19
Updated: March 29, 2020 21:15 EDT
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COVID-19 Epidemic Curves for Selected Countries
COVID-19 Epidemic Curves for six countries (China, Iran, S. Korea, Italy, United States, and Japan) showing the period March 15–29. Note that the left axis is logarithmic rather than linear and represents the cumulative number of cases reported to WHO by each country. The availability of COVID-19 testing and speed of reporting cases to WHO influence the slope of each line, especially in the initial days of reporting. However, the overall slope of the line in the epidemic acceleration phase (compare Japan to others) and the time of graph "flattening" (compare S. Korea to others) are areas that are influenced by public health measures.
Graph by: Unbound Medicine
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.
- Epi curves typically display a graph of the onset of illness among cases in an outbreak. In a point-source outbreak of a known disease, for instance, an epi curve can identify the most likely time period of exposure that led to the outbreak.
- For the COVID-19 outbreak, major agencies display cases differently:
Flattening the Epidemic Curve
- 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.
Global Epidemic Curve for COVID-19
U.S. Epidemic Curve for COVID-19
Infographics and Tutorials
- Interactive tutorial on epidemic curves – from the CDC
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- Coronavirus Disease 2019 (COVID-19) Situation Reports. World Health Organization. [https://www.who.int…]
- Total confirmed cases of COVID-19. Our World in Data. [https://ourworldindata.org…]
- Interpretation of Epidemic (Epi) Curves during Ongoing Outbreak Investigations. US Centers for Disease Control and Prevention. [https://www.cdc.gov…]
- Coronavirus Disease 2019 (COVID-19) in the U.S. United States Centers for Disease Control and Prevention. [https://www.cdc.gov…]
- 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]
- Quick-Learn Lesson: Create an Epi Curve. US Centers for Disease Control and Prevention. [https://www.cdc.gov…]