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A note of caution about confirmed case numbers. COVID19 vs Flu

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  • A note of caution about confirmed case numbers. COVID19 vs Flu

    A note of caution about confirmed case numbers.

    I’ve seen lots of people recently comparing coronavirus and flu numbers so I want to do a dive in to each.

    The US publishes an Influenza surveillance update (FluView) each week. https://www.cdc.gov/flu/weekly/index.htm The most recent was published on Feb 27 and covered week 8, the week ending Feb 22 so it’s already a little out of date.
    The data for week 8 indicates 42,587 cases were tested and 11,249 were positive for flu. The CDC also publishes a weekly estimate on the number of flu cases, hospitalizations and deaths in the US. https://www.cdc.gov/flu/about/burden...-estimates.htm The latest estimate was also published Feb 27 and covered the period up to week 8. Between weeks 7 and 8, an estimated 3-4 million influenza cases were added. In other words, CDC testing captures a very tiny 0.4% of all cases.

    Let’s look at hospitalization data. Fluview gives 15,319 confirmed influenza-associated hospitalizations between October 1 and Feb 22. This is an increase of 1,544 over the previous week. In contrast, the CDC estimates that 30,000-60,000 flu hospitalizations actually occurred that week. A figure at least 20 times higher than the captured number. The reasons for this are manifold, but one scenario plays out as follows; someone contracts flu, fights it for a few days, immune system is stressed, overcomes the flu, but develops pneumonia that requires hospitalization. By the time testing is performed, the flu virus is long gone.

    And finally, mortality data. Little known fact, the Week 8 FluView does not give week 8 mortality data. It always gives data from the previous week due to serious lags in compilation and reporting. The data presented represents week 7 (ending Feb 15). Going to the original source of this data, https://gis.cdc.gov/grasp/fluview/mortality.html you find that at the time of publication (Feb 27), the week 7 data (ending Feb 15) was still only 82.3% complete. Still, 313 coded influenza and 2,401 coded pneumonia deaths happened that week. Using CDC estimates for weeks 6-7, an estimated 2-5,000 influenza deaths actually occurred that week.

    In summary, 42,587 influenza tests discovered at best 0.4% of estimated cases, 5% of hospitalized cases, and 16% of fatal cases.

    On Feb 16, the CDC reported that they had performed a total of 479 Coronavirus tests with 15 positives https://flutrackers.com/forum/forum/...296#post830296 , this number dropped to 413 on Feb 20, but increased by Feb 23, to a total of 426 tests performed with 53 positives including 39 repatriated persons from Wuhan (3) and the Diamond Princess (36). I’m guessing that the reduction is due to the realization that the test was faulty, and some test results were thrown out. Either way you are looking at the most at a few dozen tests performed during that week.

    What fraction of cases & fatalities do you think those tests captured?


    Resources:
    Archived flu mortality data & estimates for 2019-20 https://flutrackers.com/forum/forum/...illance-system
    Archived FluView 2019-20 https://flutrackers.com/forum/forum/...luview-2019-20
    Twitter: @RonanKelly13
    The views expressed are mine alone and do not represent the views of my employer or any other person or organization.

  • #2
    Excellent tutorial, Ronan. Thank you.
    I'm sure that in the Seattle area we have missed hundreds of cases by now, if not more. I'm just saying hundreds because that is an expert analysis I saw. Fatalities is a tough one right now. The first death was found by a hospital that is a designated assessment hospital. They used clinical judgement since he did not fit the travel/contact risk criteria.
    Update: I saw a longer interview with the head doctor at Evergreen in Kirkland, where the first US death happened. They DID get an updated criteria on Tuesday. They are supposed to test all unexplained respiratory illnesses.
    Last edited by Emily; March 2, 2020, 03:51 AM. Reason: Update on testing criteria.
    Never forget Excalibur.
    “‘i love myself.’ the quietest. simplest. most powerful. revolution ever.” ---- nayyirah waheed
    Avatar: Franz Marc, Liegender Hund im Schnee 1911 (My posts are not intended as advice or professional assessments of any kind.)

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    • Ronan Kelly
      Ronan Kelly commented
      Editing a comment
      Thanks Emily!

  • #3
    Also, nobody outside of possibly China was testing in December and yet how many thousands were freely traveling to and from Wuhan before the WHO was notified? Now it is speculated that the virus adapted to humans last October, possibly earlier.

    I wonder if tissue samples from P&I deaths that occurred through mid-January outside China will be tested for COVID?
    "I know God will not give me anything I can't handle. I just wish that He didn't trust me so much." - Mother Teresa of Calcutta

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