CA governor projecting 25.5M COVID19 cases in CA in 8 weeks [pdf]
There are 1030 known positive CA cases right now according to the JHU map.<p>The governor&#x27;s letter is using a doubling time of 4 days, but there&#x27;s good reason to believe this 4-day time is due to recently increased testing.<p>If the governor instead takes the best-guess mean doubling time from several epidemiological studies[1] of 6.4 days, then, you would have to assume there are are 38.5 actual cases for any one tested positive case right now in order to get to 25.5M.<p>(25.5 * (10 ^ 6)) &#x2F; (1030 * (2 ^ ((7 days&#x2F;wk * 8 wk) &#x2F; 6.4 days_to_double))) = 38.46742327016<p>So to get there, the governor has to be assuming that the current measures being put in place will do absolutely nothing, and also assuming almost actual 40 cases per real case, which is quite possible.<p>If you assume the 4-day doubling time they quoted will continue for 8 straight weeks, and the number of current cases is accurate (again, probably not - probably an underestimate), you still just get to 16.9M cases.<p>Seems to me the more likely situation is that:
 (1) there are more cases than we think right now (Maybe not 40x, but maybe 10-20x?).  
 (2) the doubling time will be affected quite A LOT by the measures being put in place. It might drop the R0 to close to 1.<p>In that case, I would expect the enacted measures to at least half the R0 starting from this week, beginning of a flattening of active case count starting at this point.<p>That new R0 would hugely affect doubling time. But even conservatively estimating that R0 only goes down by 25% vs 50%, in 8 weeks time the projection of cases in CA would still be reduced by almost 60x.<p>TLDR - Best guess 8 weeks from now, CA has between 400k-1M cases. But not anything close to 25.5M. You can downvote me in 8 weeks if I&#x27;m wrong. Hopefully, the real number is closer to mine than to Gov. Newsom&#x27;s.<p>[1] <a href="https:&#x2F;&#x2F;www.thelancet.com&#x2F;journals&#x2F;lancet&#x2F;article&#x2F;PIIS0140-6736(20)30260-9&#x2F;fulltext" rel="nofollow">https:&#x2F;&#x2F;www.thelancet.com&#x2F;journals&#x2F;lancet&#x2F;article&#x2F;PIIS0140-6...</a>