# Noting the 3 week periodicity of recent cases

**URL:** <https://boards.straightdope.com/t/noting-the-3-week-periodicity-of-recent-cases/931212>\
**Category:** The Quarantine Zone\
**Tags:** covid-quarantine\
**Created:** [January 22, 2021, 2:16pm UTC](https://boards.straightdope.com/t/noting-the-3-week-periodicity-of-recent-cases/931212 "2021-01-22T14:16:34Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\
**Post date:** [January 22, 2021, 2:16pm UTC](https://boards.straightdope.com/t/noting-the-3-week-periodicity-of-recent-cases/931212/1 "2021-01-22T14:16:34Z")

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We became aware early of the weekly periodicity of reported cases and deaths. THis appears to be an artifact of reporting. THere is a spike every 7 days in both reported cases and reported deaths.

I note now from here: [United States COVID - Coronavirus Statistics - Worldometer](https://www.worldometers.info/coronavirus/country/us/) a periodicity of about 3 weeks in the reports. I would venture a guess that these have something to do with Halloween, Thanksgiving, and Christmas; but I’m not really convinced. I don’t see a similar spike coming up related to new years, and halloween didn’t seem to be a popular holiday to break quarantine.  
Anyway, has anyone else noted this? It could be just noise…3 data points is not a strong trend…but any thoughts on what is happening, other than randomness?

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**Author:** ![Fretful\_Porpentine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fretful_porpentine/32/2873_2.png) [@Fretful\_Porpentine](https://boards.straightdope.com/u/Fretful_Porpentine)\
**Post date:** [January 22, 2021, 5:11pm UTC](https://boards.straightdope.com/t/noting-the-3-week-periodicity-of-recent-cases/931212/2 "2021-01-22T17:11:37Z")

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If I’m understanding what I think you’re saying correctly, that looks like it’s clearly Thanksgiving, Christmas, and MLK Day. (Not “new infections that took place _because_ of those holidays,” to be clear, but “days when reporting is lagging behind actual cases because it’s a federal holiday and lots of people aren’t at work.”)