Figure 2a shows a sharp decline in transmission among children (dotted) over the past 3 weeks with the smallest gains being observed among the elderly (solid). While difficult to draw causal conclusions, recent mask mandates in certain districts, aggressive case identification, and limited classroom closures are likely helping as the steepest declines were among school-age children 5 – 19 years (Figure 2b). Rumor has it that an important outbreak analysis of schools with and without mask mandates is imminently expected in the MMWR. A judge presiding over the challenge to Arizona’s prohibition of school mask mandates intends to rule before the September 29^th date the law will take effect. Slower declines among working-age and older adults is likely one factor contributing to stubbornly high COVID-19 hospital occupancy (see following sections).

Comparing school reopening this year (in-person) with last year (virtual), levels of community transmission are much higher this year than last, particularly among those <15 years (Figure 2c). Higher transmission among those 15 – 24 years associated with university re-openings was first observed about this time last year (orange bars, ages 15 – 24). Transmission on campus is not an outlier this year which is consistent with the data reported on the UA COVID-19 Dashboard which indicates fewer reported cases on campus this year than last.

Over the past month, the trajectory of the current outbreak and that of the winter 2020/2021 outbreak have meaningfully diverged (Figure 2d). We are now experiencing a more permanent shift away from last year’s trajectory. Nevertheless, future continued improvements are less certain this week than last.

Test positivity among those undergoing traditional nasopharyngeal testing remain unexpectedly high at 22% (Figure 3). This level of positivity indicates that testing is negligently inadequate for public health practice and that many cases are going undiagnosed. Prior troughs in test positivity have preceded increasing transmission rates, so it is possible improvements could slow or reverse in response to Labor Day. Alternatively, fewer people may have been willing to test over the holiday raising the positivity rate but not necessarily transmission.

As of September 15th, 2050 (23%) of Arizona’s 8747 general ward beds were occupied by COVID-19 patients, a 1% decrease from last week’s 2061 occupied beds (Figure 4 and Figure 5 Panel A). Another 695 (8%) beds remained available for use. The number of available beds is similar to last week’s 689 beds.

As of September 15^th, 565 (32%) of Arizona’s 1743 ICU beds were occupied by COVID-19 patients, a 1% increase from last week’s 561 occupied beds (Figure 4 and Figure 5 Panel B). An additional 143 (8%) ICU beds remained available for use, the same as last week’s 143 beds.

As a lagging indicator, hospital occupancy is plateauing but not declining as expected. This may be attributable to persistently high transmission among high-risk groups and/or longer length of stay among younger patients.

Arizona hospital occupancy remains above seasonal levels. Safety margins, as measured by excess available beds, remain quite low (Figure 6). Available excess capacity is nearly as low as it was at the worst of the winter 2020/2021 surge. Because occupancy is not improving in response to declining community transmission, hospitals should be prepared for >20% ward occupancy and >25% ICU occupancy for several more weeks. Even if you are vaccinated, the tail of this COVID-19 surge will still impact your access to healthcare services should you become ill.

Arizona continues to experience >100 COVID-19 deaths per week (Figure 7). The week ending September 5th has recorded 180 deaths so far with the week ending August 22nd close behind with 178 deaths. Even so, the rise in the number of deaths is more muted than expected given the rise in cases. It now appears unlikely that Arizona will reach 300 deaths per week. Instead, the peak should occur at 200 deaths or a bit more per week.

For the week ending September 12th, 1712 Pima County residents were diagnosed with COVID-19 a 4% decline from last week’s initial tally (Figure 8). This marks the 3rd week of declining case counts although the decline is more modest than the state trend.

New cases are being diagnosed at a rate of 165 cases per 100K residents per week and is declining by 13 cases per 100K residents per week. Trends across the various age groups appear in Figure 9. A sharp, sustained drop among children, but not others, is readily apparent.