Some screenshots from a canadian website:

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See this sinusoidal shape? Why is it there? Shouldn't it be a single curve?

My main guess is when cases are counted: is it possible that they are counted something like every monday or so? I can't believe the virus progression really has sinusoidal-shaped curve.

It is not an error in the website, since other sources seem to show the same thing: worldometers, nbc news, and many others


1 Answer 1


It's a weekly cycle due to reporting disruptions over the weekend.

Use a 7-day moving average to get a better picture. Holidays and such can still be disruptive but the 7-day average solves most of it.

  • $\begingroup$ That's what happened in the UK. Most hospitals didn't report on Saturday / Sunday / Bank holidays, a small number did. The results published were based on the reports of the day before. So Saturday result = normal, Sunday result = low, Monday results = low (because little got reported on Sunday), Tuesday results = very high (most of Saturday / Sunday got reported on Monday), Wednesday results = slightly high (some hospitals didn't manage to report everything on Monday). $\endgroup$
    – gnasher729
    Commented Dec 29, 2022 at 10:08
  • $\begingroup$ And then we had newspapers that reported every weekend how we are beating the virus because the numbers dropped, and every Tuesday how we were struck by total disaster because the numbers went up. $\endgroup$
    – gnasher729
    Commented Dec 29, 2022 at 10:10

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