The outbreak remains broadly entrenched with increases among all age groups. However, the transmission rate among those >64 years of age is concerning given that it is 50% higher than the summer outbreak (Figure 2).

Note: Data for this report was updated Friday, December 4 allowing 4 full working days to adjudicate weekend cases. This should reduce week-over-week backfill to <10% allowing more interpretable comparisons and graphics. All comparisons are week-over-week changes. Given the lengthy reporting delays, future updates will continue to be released on weekends.

Test positivity among those undergoing traditional PCR testing continues to increase, reaching 21.8% this past week (Figure 3). Increasing test positivity indicates that viral transmission continues to increase despite the uncertainty surrounding actual case counts. Test positivity for antigen tests being conducted by the University of Arizona and by some long-term care facilities and retail clinics was 19.0% this week. Test positivity for saliva testing being conducted by Arizona State University for students and other groups was 16.1% this week.

As of December 4th, 2931 (34%) of Arizona’s 8666 general ward beds were occupied by Covid-19 patients, a 23% increase from last week’s 2383 occupied beds (Figure 4 and Figure 5 Panel A). Another 861 (10%) beds were available for use. This is lower than the 1213 beds available during the week of Thanksgiving.

For reference, max Covid-19 ward occupancy was 3517 beds on July 13. If similar weekly increases persist, the previous peak will be reached by Friday, Dec 12th.

As of December 4th, 701 (40%) of Arizona’s 1743 ICU beds were occupied with Covid-19 patients, a 27% increase from last week’s count of 553 patients (Figure 4 and Figure 5 Panel B). An additional 144 (11%) ICU beds remain available. This is lower than last week’s 196 beds.

For reference, max Covid-19 ICU occupancy was 970 beds on July 13th. If similar weekly increases persist, the previous peak will be reached before Friday, December 19th.

Arizona hospitals’ safety margin continues to erode in both the ward and ICU (Figure 6). Hospital occupancy is high not only because of Covid-19 admissions but also because hospitals continue to perform scheduled procedures and because of higher occupancy this time of year due to wintering part-time residents and viral respiratory season.

While occupancy data suggest Arizona hospitals should be under greater strain, the fact that admissions are dispersed across multiple units, not just Covid-specific units, means the workload is more evenly distributed across physicians, nurses and other health professionals. As Covid-19 admissions continue to increase, this advantage will be lost.

With 617 deaths, the week ending July 19th remains Arizona’s deadliest week (Figure 7). Weekly Covid-19 mortality reached a nadir of 46 deaths the week ending October 4th. Because cases have been increasing, deaths are now increasing. Sharper rises are expected over the coming weeks as deaths lag new cases by 14-days and are often only made known weeks later. However, the case fatality rate has held relatively stable at 1.7%. By Christmas, Arizona will be experiencing >500 deaths per week (30000 weekly cases now times .017 = weekly deaths 2 – 3 weeks from now). However, this toll will not be apparent until mid-January when all deaths are accounted for. Unidentified Covid-19 deaths (e.g., excess mortality) are not included in this estimate.

For the week ending November 29th, 3762 Pima County residents were diagnosed with Covid-19 (Figure 8). This represents a 3% increase from the 3660 initially reported last week. This tally once again sets a new record for cases observed in a single week. Test reporting remains relatively timely and case reporting delays only caused last week’s initial tally of 3660 cases to be upwardly revised by 4% (146 cases) this week.

However, the sharp decline in testing suggests additional cases were missed or will be backfilled next week. Increases in viral transmission are occurring across all age groups (Figure 9).

There was no update this week to the ASU Covid-19 model of projected cases, hospitalizations, and deaths through mid-January (full report). The current data continue to track as expected (Figure 10). The main findings are summarized in Figure 10. Assuming current viral transmission rates continue unabated, total Covid-19 hospitalizations in Arizona could exceed the total number of hospital beds by Christmas; however, it is looking more likely to be early January before this could happen (green line). This change does not reflect increases that might occur because of Thanksgiving travel and gatherings.

**A special thank you to the members of the ASU Covid-19 Modeling Group for their efforts to bring greater understanding of the current outbreak and for sharing their report. Readers are encouraged to read the full report which can be found here.