27 August 2020 Blog Post: COVID-19 Update in Los Angeles County

Headlines such as the one in the linked article below (“Coronavirus trends falling in LA County; health officer says he knows why”) make me very nervous. I think there are a couple of reasons behind my trepidation. First off, I think cautious optimism should be expressed exactly as such. Secondly, the Los Angeles County Health Department doesn’t have the best COVID-19 track records. They mistakenly opened up in person activities such as gyms in mid-June when case rates plateaued but had not dropped. That (and the July 4th weekend) led to the sharp increase in cases through July.
Dr. Davis states – “Cautious reopening means we take to heart the lessons we learned from July and move forward in a new normal of making the infection-control practices part of our day-to-day lives for the foreseeable future.”
Here’s the problem I am having with Dr. Davis’ approach – I don’t at all feel comfortable with the shape of Los Angeles County’s epidemic curve (Figure 1 below). Typically an epidemic curve will follow an S-shaped distribution. Remember months ago when ‘flattenning the curve’ was drummed into our collective consciousness? Well the LA County case curve is no longer flat – it has been decimated. From the 7/17 case peak until now, 5 weeks later, we have dropped back to pre-July surge rates. This is not the usual pattern for an epidemic curve. 
We see a similar trend with mortality rates as well (Figure 2). The drop from 8/7 until 8/21 is really astonishing with almost a 50% decrease in deaths due to COVID-19. But look at the pattern from the May peak of 0.44 deaths per day per 100,000 population – mortality rates slowly trended down over a 6 week period. Now we have learned quite a bit since that time in how to care for severe COVID-19 cases so perhaps this steep drop in mortality is due to better care. Certainly that is one plausible explanation.
But the last curve (Figure 3) is the one that concerns me the most – testing rates. These are down 33% from their mid-July peak. To me it is not surprising that we are seeing fewer cases in the context of less testing. I would be far more convinced of a true decrease in COVID-19 in the County had testing not dropped off so dramatically.

𝗦𝗶𝗴𝗻 𝗨𝗽 𝗳𝗼𝗿 𝗢𝘂𝗿 𝗡𝗲𝘄𝘀𝗹𝗲𝘁𝘁𝗲𝗿

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