Letter: Lake Tahoe Region has three times the number of new COVID cases as El Dorado County

If the Lake Tahoe Region of El Dorado County were its own county, it would be solidly on the state watch list, as its new case rate is even higher than LA County’s rate. Furthermore, El Dorado County should be on the watch list, but it is not. As a result, people think it is safe in Tahoe and thousands of visitors are continuously bringing the virus into the area, overwhelming our health system, and exposing residents.

A county makes the watch list if it has a new case rate of more than 100 new cases per 100,000 people over the past 14 days, but there are different ways to count this case rate. The more common way, used by El Dorado County and the LA Times, is to count the number of cases reported each day over the past 14 days. Using this approach, El Dorado County has been over the watch list threshold since July 21st, and Tahoe since June 29th.

The state uses a different approach that undercounts cases and keeps El Dorado County below the 100-case threshold. The state assigns each new case to its “episode date,” which is the earliest that one of the following events occurred: the patient was tested, showed symptoms, was diagnosed, was hospitalized, or died. Then it allows for only a 3-day testing lag and counts cases by episode date over the previous 14 days. For example, to calculate the rate on August 14 the state includes new cases with episode dates from July 28 to August 10.

But a 3-day lag is not long enough to include all new cases. For new cases reported in El Dorado County on Aug 14th, the corresponding episode dates go as far back as July 11th, and total counts for episode dates after July 30 are not complete. In other words, there is a 15-day lag instead of a 3-day lag. This means that most El Dorado County cases are never included in the state’s calculation of the new case rate. A case reported on Aug 14 for a patient that went in for a test on August 1 but first showed symptoms on July 27 (the episode date) would not be included. In fact, this case would never show up in the state’s new case rate.

As a result, El Dorado County – and the Lake Tahoe Region - may never make the state watch list. Using the more complete method, El Dorado County reported a new case rate of 105 for August 14th. Tahoe’s rate is three times higher, ranking it as the 22nd highest rate among 58 California counties.

Unfortunately, Tahoe suffers from lack of recognition of its COVID severity. Local leaders are not taking adequate measures to protect the community. Larger than normal crowds continue to flood our community, and many people are still not wearing masks. Many high-risk locations are still open. Even while COVID may decline elsewhere, it will continue to flourish under these conditions, prolonging the risk to our community.

These numbers are publicly available and so there is no excuse for the lack of local response to reduce transmission in the Lake Tahoe Region. El Dorado County is thankfully posting a fairly complete set of daily statistics that shows the reporting lag and the Tahoe COIVD surge (see https://edcgov.us/Government/hhsa/Pages/EDCCOVID-19-Cases.aspx). I used these statistics, along with 2018 census data, to estimate that Tahoe’s case rate is three times that of El Dorado County’s rate, and to determine the total reporting lag. It would be nice if El Dorado County would provide the full set of numbers for each region (episode date time series, case rates, etc.).

- Alan Di Vittorio