There was a surge in epidemiologists saying there would be a surge in post holiday cases of Covid-19. There was also a surge in news reports saying that California’s expanding cases were due to the holiday surge.

Except that was not true.

Let’s take a look.

  • Peak day of new cases was Dec 20th.
  • The 2nd and 3rd highest days were Dec 17 and Dec 18th.
  • The 7-day moving average peaked on Dec 22.
  • Cases began rising in October and rose steadily thereafter.

Cases then began falling. BEFORE CHRISTMAS.

Note that the rise in cases began in late October and rose at a steady, slightly exponential rate. The daily fluctuations have to do with fewer tests done on holidays (like Thanksgiving weekend) and delays in collecting reports through holiday periods. Look carefully and you can see the large white line between Dec 8 and Feb 1 – that is December 25th. Few people were tested and/or the reports did not get processed right away.

The 2nd peak is about Jan 8 to Jan 10th. As colleges and universities resumed after the holidays, most tested all returning students (including often both on campus and off campus) and all staff members, causing a rise in positive tests due to just testing more people.

To illustrate – here is the increase in cases at two state universities showing the peaks in the first weeks of classes:

Another problem is they are using a diagnostic test on asymptomatic populations producing sizable numbers of false positives. (WHO has since issued new guidelines to help prevent false positives – however, the colleges in my area were not following those guidelines to reconfirm all asymptomatic positive tests.)

Nationally, the peak day of new cases was also before Christmas.

What happened was epidemiologists made intuitive statements not based on data. It was easy to show a random correlation that kinda sorta felt right – but wasn’t. Another way to think about this is to look at the epicurves of the many states that had peaked earlier or later – and had no specific correlation with Christmas holidays. It was luck of the draw that California peaked near the holidays, and sloppy science pretended to see a correlation that wasn’t.

I hope this post puts an end to the surge in epidemiologists and news reports proclaiming a holiday surge in cases.

I am a brain injured idiot who knows nothing about health care. I make observations and ask stupid questions.

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Coldstreams Skeptic