1. As we look to the coming winter in the Northern Hemisphere, 2 big Qs loom. What's going to happen with Covid? & Will #flu return in a significant way this winter?
@WHO's biweekly flu update suggests transmission remains at low levels globally.
All data below are from @WHO.
2. There are smatterings of #flu here and there around the globe. Some flu B in the Caribbean & Central America. Some flu A in parts of Africa and Asia.
3. How much #flu is out there? Of nearly 276K flu tests run in 88 countries from 8/30-9/12, 1,884 were positive for flu — 0.68%.
During the same 2-week period in 2019 (ie before Covid) 7.4% of tests globally were positive for influenza. In 2020, it was 0.04%, ie almost none.
4. Aside: Another Q about #flu is whether a family of flu B viruses, B/Yamagata, was driven extinct during the pandemic. Two B/Yam viruses were reported in this @WHO report but as @trvrb would say, let's see if sequences get logged into the databases. TBD. statnews.com/2021/06/02/pan…
5. I wanted to see how 0.68% test positivity compared to the rest of the pandemic. The main graph is Aug 2019 (to the left is the 2019-2020 flu season; very active) through Sept 2021. Flu vanished in April 2020. The inset is then on. We're still not back to April 2020 flu levels.
6. We're still not back to April 2020 #flu levels, but the percentage of positive tests is slowly rising.
A caveat I don't know how to adjust for: The denominator varies per 2-wk period. Mostly >100K, sometimes >200K tests, a few times <100K.
7. Another caveat: Pre-Covid, most #flu tests were likely ordered when someone had #flu-like symptoms. In the pandemic, I would imagine a lot of these are tests that look for Covid or flu or other respiratory pathogens. I don't know what that does to the comparability of data.
8. But any way you slice it, there's been a lot of testing for #flu during the pandemic & not much flu found. It appears to be inching (millimetering?) upwards, but it is still well below what it would normally be at this time of year.
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