COVID-19 Update in Orange County: Why OC Is Off State Watchlist – 29 August 2020

The Mercury News raises a good question in the linked article – how did Orange County come off the state’s COVID-19 watch list while the Bay Area (who has had arguably the most effective coronavirus response in the county) remains on it?

Orange County has taken some notable missteps:

1. June 8th: Residents threatening the life of health director Dr. Nichole Quick after a mandatory face covering order leading to her resignation. [Case rates increase from 5.93 cases per 100,000 population to 26.57 in the month that follows].
2. June 22nd: Sheriff refuses to enforce a face covering mandate saying “We’re not the mask police.” Case rates double from 11.95 to 22.37 that week.
3. July 14th: Orange County Board of Education votes 4-1 for a return to school with no masks and no distancing. Note in their remarks that masks are ‘harmful’. Case rates and mortality rates are at their highest levels since the pandemic began that week.

Yet this week, despite “intense resistance to COVID-19 restrictions amid soaring case rates and hospitalizations just weeks ago has now won the state’s seal of approval to begin a partial return to normal,” according to the Mercury News.

Graphs of case and mortality rates in Orange County are presented below in Figures 1 and 2. Case rates peaked the week of July 3rd and then flattened for the following 3 weeks before starting a steep decline. This is an interesting pattern, somewhat different than that observed in Los Angeles where the case peak occurred the week of 7/17, likely reflecting increased transmission during the July 4th weekend. Given the intense resistance to COVID-19 mitigation efforts in Orange County, the July 4th holiday weekend may not have looked much different than other weekends.

Mortality rates, as expected, take longer to decline given a several week lag time between infection and progression to severe disease. Mortality rates peaked in Orange County in early August and only now are beginning to decline.

But while epidemiologists are concentrating on case and mortality rate graphs, I think the secret to Orange County’s success is in testing – something not mentioned in this article. Testing rates (Figure 3 below in blue) in Orange County have remained above 180 daily tests per 100,000 population since late June. There have been some modest peaks and valleys over the past 8 weeks, but rates remain robust with only a slight downtrend downtrend. I have plotted Los Angeles County testing rates in red; testing has dropped by one third since its 7/17 peak in LA.

Declining case rates in the face of stable testing rates is far more reassuring for opening than lower case rates with less testing.


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