AZ Pandemic Numbers Summary for the Seven Days Ending March 15: Mixed Bag

 

Here are the Arizona pandemic numbers and graph of statewide cases for the seven day period ending Wednesday:



This week's numbers are a mixed bag. Cases are down a little in Maricopa County and up a little more statewide. Hospital beds are up a little.

Deaths increased 115%, but I'm calling B.S. on that one. Probably another stale data dump from AzDHS. We will see next week.

All the wastewater signals are down except Yavapai County. We don't know what the level is in Tempe because once again they are late updating their dashboard. [Updated on 3/17 with Tempe data]

After last week's summary, there was some discussion on Reddit CoronavirusAZ about wastewater numbers. I mentioned that they didn't always seem to me to track the other indicators, and I said I would investigate

I have 47 weeks of data that include wastewater levels. The areas included in that have expanded over time so I just calculated the average of whatever numbers I had for a given week and plotted that against hospital beds (the only really reliable number we have for serious cases). Here is the result:


If we exclude the outlier cases (circled) the correlation here is 0.78, which is a very large correlation. Here is the caveat: It is a zero-order correlation, i.e. it is for the beds for a given week and the wastewater values for the same week.

People who are sick are shedding virus in their feces from the start, but it takes time for the disease to worsen enough for them to go to the hospital. So there should be some lag in the correlation. But I checked the one-week lag (i.e. hospital beds this week vs. wastewater average last week), and the correlation went down.

One possible explanation is that all the wastewater values come with reporting lags (see notes on the table). So it might be that this lag allows for the development of serious disease already. 

I am trying to get an epidemiologist I know to consult on this. If I succeed I'll post more here next week.

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