Arizona likely surpassed the 30,000 cases per week (4,000 per day) threshold this week. This outbreak continues to be broadly entrenched with rapid increases among all age groups including those over 65 years of age (Figure 2).

Note: Data for this report was updated mid-morning Friday, November 27 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.

Figure 2. Newly Diagnosed Covid-19 Cases in Arizona by Age Group March 1 through November 22.

Test positivity among those undergoing traditional PCR testing continues to increase, reaching 17.0% this past week (Figure 3). Increasing test positivity provides additional evidence 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 14.4% this week. Test positivity for saliva testing being conducted by Arizona State University for students and other groups was 8.3% this week.

Figure 3. Weekly Number Patients PCR Tested and Percent with Positive Test March 1 – November 22.

As of November 27th, 2383 (28%) of Arizona’s 8651 general ward beds were occupied by Covid-19 patients, a 24% increase from last week’s 1916 occupied beds (Figure 4 and Figure 5 Panel A). Another 1213 (14%) beds were available for use. This is higher than the 944 beds available last week owing to fewer scheduled admissions over the holiday week.

Figure 4. Arizona Daily Covid-19 General Ward and ICU Census April 20 – November 27.

As of November 27th, 553 (32%) of Arizona’s 1751 ICU beds were occupied with Covid-19 patients, a 27% increase from last week’s count of 435 patients (Figure 4 and Figure 5 Panel B). An additional 196 (11%) ICU beds remain available. This is higher than last week’s 174 beds.

Figure 5. Covid-19 Occupancy as a Percent of Listed General Ward (A, left) and ICU (B, right) Capacity in Arizona April 20 – November 27.

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.

Figure 6. Observed Excess Non-Surge General Ward and ICU Capacity April 20 – November 27.

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 trending up and are near those last observed in May.

Figure 7. Weekly Known Arizona Covid-19 Deaths March 1 – November 22.

For the week ending November 22nd, 3660 Pima County residents were diagnosed with Covid-19 (Figure 8). This represents a 39% increase from the 2624 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 2041 cases to be upwardly revised by 2% (56 cases) this week.

Figure 8. Covid-19 Cases and Individuals Undergoing Diagnostic Testing in Pima County Mar 1 – Nov 22.

Increases in viral transmission are occurring across all age groups (Figure 9).

Figure 9. Covid-19 Cases by Age Group in Pima County from August 9 – November 22.

This “new” deviation is evident in Figure 10 below where actual observed hospitalizations (orange dots) increased faster than predicted (orange line). This observed deviation led the ASU team to update their model.

 

This new model assumes 3 scenarios: current transmission rates remain unabated (β = 0.245), transmission accelerates (β = 0.282), or transmission declines (β = 0.208). The team’s best fit assumes that transmission will continue unabated. The low and high assumptions reflect arbitrary deviances around their best-fit estimate.

Figure 10. ASU Covid-19 Modeling Group Estimate of Hospitalization in Maricopa County through January 21st (November 20 Update).

Assuming current viral transmission rates continue unabated, total Covid-19 hospitalizations in Arizona could exceed the total number of hospital beds by Christmas (Figure 11). This change does not reflect increases that might occur because of Thanksgiving travel and gatherings. If such increases occur, then total capacity could be exceeded even sooner.

If this were to happen, it would represent a humanitarian crisis of unparalleled proportion and would be accompanied by hundreds if not thousands of preventable deaths. In addition to degrading care for those with Covid-19, this crisis would also threaten to delay or prevent those with serious medical conditions from accessing care as well. Allowing a crisis of this magnitude to occur is unthinkable.

In this regard, Arizona should reinstate its shelter-in-place order for the post-Thanksgiving – Christmas period. While more targeted restrictions could have slowed transmission if implemented weeks ago, the potential consequences of an outbreak of this size and trajectory are too dire to rely on half-measures now. Of course, such restrictions will impose severe economic hardship on businesses and families at a time when state and federal governments are doing little to ameliorate them. Therefore, it is imperative that the state also expand its efforts to alleviate food insecurity, to prevent evictions and foreclosures, and to protect access to health services.

Figure 11. ASU Covid-19 Modeling Group Estimate of Total Covid-19 Hospitalization in Arizona through January 21st. Produced by Esma Gel, PhD, Megan Jehn, PhD, Anna Muldoon MPH, Health Ross, PhD, DNP, ANP-BC, and Tim Lant, PhD, MAS (November 24 Update).