In my opinion, the 2019-20 flu season did not come to an abrupt end due to viral interference.

Positive tests for flu & other respiratory viruses dropped because associated testing dropped with the focus on/capacity "needs" for SARS-CoV-2 testing.

This has long been my hypothesis, but the best real-time confirmatory testimony I've found is from a 4/6/20 presentation by Dr. James Crawford of Northwell Health Labs, New York, via CDC phone call.
▶️ Crawford: "You can see on the left that we had, in essence, a usual rate of RVP [Respiratory Virus Panel] testing during the flu season. The green is total tests. The red is a positive for a routine respiratory virus. And a gap started opening up on March 3."
⏸️ Pause

Note that Dr. Crawford doesn't say what those "routine respiratory virus" positives are.

Nor does he say why more RVP tests are being administered.

But data for NYC Emergency Department visits ILI (Influenza-Like Illness) give us a hint...
📉 Feb 29, 2020 - ILI visits were down.

The next day, March 1st, officials announced the city's the "first" positive Covid test.
📈 And snap! ED Visits for ILI shot up.
⏸️ Back to this graph for Northwell

Seems fair to deduce the rise in test was fueled by the rise in visits for ILI...which were likely fueled by the public & congregate settings reacting to the 3/1/20 news about the covid case & increasing frenzy.
▶️ Crawford, continued, referring to the SARS-CoV-2 test:

"We turned on our CDC assay March 8. We turned on our semi-automated March 11. And you can see this huge gap in negativity opening up with our RVP testing, what I call the COVID-19 gap."

*annotations mine
▶️ "And in that gap, the majority, a slight majority it's about 55% to 60%-- test positive."

That's a high % positive for a virus that allegedly just arrived.

No info given re: co-infections
▶️ "This is important," Crawford continues. "RVP testing uses up real estate on your machinery, particularly if you're using the semi-automated machines in your hospital sites."

Pay attention to the next part. ⬇️
▶️ "And so we have discouraged use of RVP testing in favor of COVID testing, just to ensure that we're optimizing our laboratory resources"

In other words, testing for the *new* virus was more important than testing for the typical viruses

Fewer RVP tests = Fewer detections
▶️ Crawford: "Another problem we hv on the right [graph] is the fact that hospitalized patients with fevers, the doctors will order blood culture.

While our central microbiology lab is built for around 18K blood bottles per day for a two week period, we exceeded..."
▶️ "...what was a reasonable capacity for blood cultures and were at risk of not being able to provide results should any of our machines gone down. 😳 And you can see on the same scale the amount of COVID testing that was done."
▶️ "We've been messaging very strongly that physicians shouldn't order blood cultures on COVID pts unless there is reason to suspect super infection...fortunately, w/this messaging...the blood culture util. has gone back to...normal values."

[👀 to Covid test orders in Feb ⬇️]
Northwell's RVP testing data (and Dr Crawford's saying RVP testing was being discouraged due to capacity) is consistent with CDC data on tests given for common HCoVs. Note the spike, followed by drop-off.
Authors: "Weekly testing volumes were higher during March 2020, the onset of the COVID-19 pandemic, than during any other week in July 2014 and November 2021"
Authors, cont: "Among the limitations of this investigation, testing patterns for respiratory viruses changed during the 2020–21 season because of delayed routine healthcare and an emphasis on SARS-CoV-2 testing, which affects comparison with earlier seasons."
For cities/states that report the number of flu TESTS GIVEN weekly, I haven't yet found one that didn't see a sudden drop in March or early April 2020.
Chicago is a great example.

The testing drops, as do the positives, in those same March weeks.

SARS-CoV-2 interfered with flu, but it the interference wasn't "viral".
Remember, too, that the advent of Covid-Like Illness (CLI) Emergency Dept visits - which isn't all that different from ILI - was 3/15/2020.

Chicago shows the "handoff" very well

CLI "went away" in June 2021.

More about that on another day...
If anyone has data -- especially for a large CITY, but a state works too -- that does NOT show a sudden drop in the number of flu tests being given in spring 2020, please post.
Link to transcript & slides for April 6, 2020 CDC call. Lots of interesting things in there, besides those mentioned in this thread

That's all for now.

Please forgive any typos.

End 🧵
Exactly right.

Or, if you prefer, covid "bought out" flu for awhile.

Flu tried to clock in, but the clock was broken.

Still went to work & put in the hours tho. Didn't take a vacay.

“Early on, the pandemic disrupted influenza surveillance in most countries, although it recovered in many by early 2021.”
“'Globally, we saw as much or more testing than usual for influenza,* but many countries did struggle to maintain influenza surveillance in the face of the COVID-19 pandemic.'"
- Ann Moen, WHO Chief of Influenza Preparedness & Response

Moen cont'd: “'Some countries did not maintain influenza surveillance for a variety of reasons, such as lack of reagents, prioritization for just COVID-19 testing, and diversion of flu staff to COVID-19 work.'”


Which countries?
“Except for a few places, such as western Africa, ‘the flu was essentially nowhere’ this past fall &winter, virologist Richard Webby, PhD, of St Jude Children’s Research Hospital, 1 of 6 World Health Organization (WHO) Collaborating Centers for influenza, told JAMA.”
“Except for Western Africa”

What happened in Iran’s 2019-2020 season?

That gap is 🤔

Interruption to due to “must find covid” focused, followed by a return to flu/RVP testing b4 end of season?

Lotta “not subtyped” just before & after the break. 🤔

More data from Chicago related to the abrupt "end" of flu in spring 2020

Positive flu tests falling off a cliff was neither a suicide nor viral interference/homicide on the part of another "novel" pathogen.

“Based on published empirical evidence we think that the explanation that flu disappeared b/c of competition from SARS-CoV-2 is wrong &, given this fact, we need to look elsewhere for an explanation for flu’s disappearance.”

Via @MartinNeil9 et al
Interesting claim in comment section of⬆️article.

Tomas Hull says Biofire PCR testing machines in Canadian hospitals were "upgraded" in Mar/Apr 2020 "with a new chip to detect Covid-19."

Can anyone else confirm this occurred, either in Canada or elsewhere?
Canadian flu test data for spring 2020 support such a claim -- as well as my theory that Human Interference, vs. Viral Interference, is the culprit of positive flu tests simultaneously disappearing in many countries.

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Recommendations from around the web and our community.

Great thread with yet more evidence flu “disappeared” only due to panicked new testing protocols.