While the outbreak remains broadly entrenched, cases among those >64 years of age who are at highest risk of hospitalization, ICU admission, and mortality continues to increase relative to younger cohorts (Figure 2). For example, the proportion of total cases attributable to those >60 years of age doubled from 11% to 22% between mid-September and late-December.

Note: Data for this report was updated Monday, January 4 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 this Friday.

Test positivity among those undergoing traditional PCR testing increased from 26% the week ending December 20th to 30% the week ending December 27th (Figure 3). This new positivity record suggests that viral transmission is higher than indicated by the case counts alone.

As of Jan 4th, 4789 (56%) of Arizona’s 8604 general ward beds were occupied by Covid-19 patients, a 7% increase from last week’s 4475 occupied beds (Figure 4 and Figure 5 Panel A). Another 666 (8%) beds remained available for use. The number of available beds is lower than last week’s 765 beds.

At 4789 beds and 56% occupancy, Arizona has once again established new records for ward Covid-19 patients and percent occupancy.

As of January 4th, 1096 (62%) of Arizona’s 1777 ICU beds were occupied with Covid-19 patients, a 4% increase from last week’s count of 1053 patients (Figure 4 and Figure 5 Panel B). An additional 136 (8%) ICU beds remain available. This is lower than last week’s 154 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. Arizona hospitals are now relying less on “displacement” and more on triaging by acuity of illness to maintain manageable case loads. A number of patients who would have hospitalized 4 – 8 weeks ago are now being managed in the outpatient setting. Make no mistake, the Covid-19 crisis is now placing a greater share of Arizonans’ at-risk, not just those unfortunate enough to contract Covid-19.

While the week ending July 19th remains Arizona’s deadliest with 617 deaths, the week ending December 20th has now recorded 613 deaths. This number will continue to increase as more deaths are made known in the coming weeks (Figure 7). Covid-19 deaths will continue to exceed 500 per week for the foreseeable future. The uniformly increasing mortality curve in Figure 7 should give us pause as it indicates that viral transmission has been steadily increasing during the holiday period despite the irregularities in case reporting.

Arizona has the fastest growing Covid-19 outbreak as measured by cases reported to the CDC in the past 7-days and the 11th fastest growing outbreak as measured by Arizona’s effective viral reproduction number. As described in this report, estimating viral transmission using reported cases is challenging owing to changes in testing patterns that occurred over the holiday period (Figure 8). Nevertheless, the preponderance of data indicate that viral transmission is increasing and will continue to do so in the coming weeks.

For the week ending December 27th, 5964 Pima County residents were diagnosed with Covid-19 (Figure 9). This represents a 24% decrease from the 7810 cases initially reported last week. However, this decline should be viewed skeptically as test reporting was sharply down during the week.

Last week’s initial tally of 7810 cases was upwardly revised by only 1% (111 cases) this week. Trends are similar across all age groups (Figure 10).