While the outbreak remains broadly entrenched, there has been some moderation among adolescents, young adults, and working-age adults. However, cases among those >64 years of age who are at highest risk of hospitalization, ICU admission, and mortality continues to increase (Figure 2). Therefore, hospitals are likely to experience increasing occupancy into early January.

Note: Data for this report was updated Monday, December 28 allowing 7 full days to adjudicate cases and keep week-over-week backfill <10%. This allows more interpretable comparisons and graphics. All comparisons are week-over-week changes. The next update will be released on Tuesday.

Test positivity among those undergoing traditional PCR testing has plateaued, at least temporarily. Last week it was 26.6%; this week it was 25.9% (Figure 3). This suggests that there has been some moderation in the pace of viral transmission despite the uncertainty surrounding the precise case count.

As of December 28th, 4475 (53%) of Arizona’s 8505 general ward beds were occupied by Covid-19 patients, an 11% increase from last week’s 4019 occupied beds (Figure 4 and Figure 5 Panel A). Another 765 (9%) beds remained available for use. The number of available beds is higher than last week’s 742 beds.

At 4475 beds and 53% occupancy, Arizona has once again established new records for ward Covid-19 patients and percent occupancy.

As of December 28th, 1053 (59%) of Arizona’s 1779 ICU beds were occupied with Covid-19 patients, a 12% increase from last week’s count of 943 patients (Figure 4 and Figure 5 Panel B). An additional 154 (9%) ICU beds remain available. This is lower than last week’s 161 beds. Covid-19 occupied ICU beds and percent occupancy have never been higher in Arizona.

Arizona hospitals’ safety margin continues to erode in the ward and ICU (Figure 6). Most hospitals have cancelled scheduled procedures to ensure adequate capacity for patients with Covid-19 care.

We are now undergoing the great “displacement” such that hospital services are now being rationed so that patients with severe Covid-19 illness are displacing others who have slightly less severe non-Covid medical conditions.

While the week ending July 19th remains Arizona’s deadliest week with 617 deaths, the week ending December 13^th has now seen 525 recorded deaths (Figure 7). This number will rise further over the coming weeks as more deaths are made known. Covid-19 deaths are expected to exceed 500 weekly for the foreseeable future and may reach a new record by late December. Recall that deaths lag new cases by 14-days and are often only known weeks later. As a rule of thumb, multiplying the number of weekly cases by 1.5%, the case fatality rate, will approximate the number of Covid-19 deaths in 2 – 3 weeks’ time.

For those keeping score, Arizona now has the 32^nd fastest increasing Covid-19 outbreak as measured by Rt.live. This is down dramatically from 10 days ago and Rt.live actually suggests Arizona’s effective viral reproduction number (Rt) is now below the important benchmark of 1.0 suggesting that viral transmission is now declining (Figure 8).

While viral transmission as measured by reported cases has moderated since early December, it is premature to believe we will see a sustained decline into January. It is more likely that Rt.live is capturing the behavioral impact of Christmas on access to testing and willingness to test. This effect is visible during Thanksgiving when the case rate declined but then quickly rebounded (Figure 9). We should be prepared for the possibility of a similar pattern repeating during Christmas. Note: Because this report tracks case counts by date of test collection it does not yet include data from Christmas week. However, Rt.live follows case counts as they are reported and does.

For the week ending December 20th, 7810 Pima County residents were diagnosed with Covid-19 (Figure 10). This represents an 8% increase from the 7237 cases initially reported last week. This tally once again sets a record for cases in a single week. 

Test reporting remains relatively timely with reporting delays causing last week’s initial tally of 7237 cases to be upwardly revised by <1% (29 cases) this week. Increases in viral transmission are occurring across all age groups (Figure 11).