Monday, March 30, 2020

Back of the Envelope Coronavirus Calculations

* I know that many of these assumptions are wrong.  This is a VERY ROUGH calculation of the order of magnitude, not an epidemiology journal article.

CDC estimates that the burden of illness during the 2018–2019 season included an estimated 35.5 million people getting sick with influenza, 16.5 million people going to a health care provider for their illness, 490,600 hospitalizations, and 34,200 deaths from influenza (Table 1).Jan 8, 2020

The Influenza Like Illness surveillance system (ILInet), which is displayed in "FluView", captures roughly 6 million visits/year.  At the peak weeks (52 and 6), 30% and 26% of samples tested positive for influenza, and 7-8% of office visits were for influenza-like illnesses.  The CDC estimates that approximately half of people with influenza seek medical care.  (All these numbers are from ILInet.) 

This flu season so far, ILInet has captured 36 million visits, of which 1.6 million tested positive for influenza overall.  This year's low estimate is 38 million cases of influenza, so ILI is capturing roughly 4% of the cases.  Let's say they're getting 10% of coronaviruses as ILI visits, for the sake of argument (yes, I have made up a number, because nobody knows).  

This past week, 6.9% of samples were positive for influenza.  So for Week 12, there were 76,654 ILI visits, of which 5289 were influenza-positive.   However, there were the same percentage of office visits for ILI as in the two peak weeks (52 and 6), even though influenza cases are decreasing. Say 25% of ILI visits were real positives, just like influenza peak, but the rest were coronavirus. Now we're at 19,000 cases, of which 14,000 were coronavirus.Now remember that we're capturing 4-10% of influenza like illnesses this way.  That's 140,000 to 350,000 cases of coronavirus last week.  
That means that a truly enormous number of people have, almost certainly, already had coronavirus in the last month.

Vote for a president who's not a clown, y'all.


  1. Yup. Anecdotally, about 50% of the people my sister knows in NYC have had it or currently have it, and none of them have been tested. That's without the asymptomatic carriers, who made up 40-50% of infected people in most studies.
    The number of actual infections will never be known, but it is staggering.

    1. Someone will eventually do a boatload of serology, but yeah. What a fucking disaster.


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