Rates are well above the threshold marking high levels of transmission signaling another substantial surge is imminent in the coming weeks. The potential size and/or duration of this surge remains uncertain but will likely be at least the size of the summer 2020 outbreak and may approach that of the winter 2021 wave. At 195 cases per 100K residents, Arizona ranks 19^th among the 50 states. Louisiana, Florida, Arkansas, and Mississippi are currently leading the pack with rates 3X higher than ours: 653, 591, 488, and 477 cases per 100K residents per week, respectively. Importantly, the rates in Louisiana have now exceeded their winter 2021 peaks and the rates in the other states are poised to set new records as well.

According to the CDC, 56% of Arizona adults have received 2-doses of vaccine while another 9% have received 1-dose. For a bit of perspective, only 43% of adults were vaccinated against influenza in the 2019-2020 season. On a positive note, about 90 thousand vaccine doses were administered last week which is 10 thousand more than the prior week and 10 thousand more than the week before that. As slow as our vaccination efforts seem, it is important to continue vaccine outreach.

Resumption of in-person instruction (K-12 and universities) in the face of high community transmission, low vaccination rates, prohibition of universal masking, lack of surveillance testing, and minimal physical distancing will undoubtedly lead to frequent school-related outbreaks and accelerating community transmission (see Pima County Health Department). This time last year, COVID-19 rates were lower, 116 versus 195 cases per 100K residents per week, and were improving, -40 versus +51 cases per 100K residents per week. Therefore, August and September are setting up to be difficult months indeed.

As K – 12 schools resume in-person instruction, it is useful to consider trends in childhood case rates (Figure 2b). Historically, children 15 – 19 years of age have had case rates approximating those of adults while prepubertal children have had meaningfully lower rates. Even though mask wearing in classrooms is recommended by the CDC and the American Academy of Pediatrics, but our state isn’t going to follow suit.

Even though considerable attention is being given to childhood cases, it is important to reaffirm that this outbreak, like past outbreaks, is being driven primarily by adolescents and working-age adults (Figure 2c). If our goal is to protect children, the most effective way to accomplish it is to slow transmission among adults.

The overall age distribution, particularly between older adults and children, has only shifted modestly since vaccines became available in December (Figure 2d). For example, children now represent about 15% of cases, up from 10% during the winter 2020 outbreak while older adults now represent about 8% of cases, down from 15% during the winter 2020 outbreak. Incomplete vaccination among older adults, but particularly among working-age adults, means that hospitals remain at risk of being overwhelmed and substantial number of deaths can once again accrue.

Test positivity among those undergoing traditional nasopharyngeal PCR testing rose to 25% this week, another meaningful week-to-week increase (Figure 3). This level indicates testing is inadequate for optimal public health practice and means many cases are going undiagnosed.

As of Aug 4th, 1266 (15%) of Arizona’s 8667 general ward beds were occupied by Covid-19 patients, a 24% increase from the previous week’s 1019 occupied beds (Figure 4 and Figure 5 Panel A). Another 887 (10%) beds remained available for use. The number of available beds is lower than the previous week’s 964 beds.

As of August 4th, 321 (22%) of Arizona’s 1722 ICU beds were occupied with Covid-19 patients, a 4% decrease from the prior week’s count of 335 patients (Figure 4 and Figure 5 Panel B). An additional 175 (10%) ICU beds remained available for use, lower than last week’s 186 beds.

Arizona hospital occupancy remains above seasonal levels. Improvements in ward and ICU occupancy remain stalled at ≥85% occupancy (Figure 6). Undoubtedly, some medically necessary procedures that were previously postponed are still being rescheduled to address the backlog of care. Occupancy will need to fall <70- 75% before conditions will be back to “normal.” However, hospitals should be prepared for >15 -20% COVID-19 occupancy for the foreseeable future as viral transmission remains high.

Now is an appropriate time to compare this outbreak with prior ones. As it happens, the most apt comparison is to the most recent winter 2021 outbreak. By my assessment, the current outbreak can be traced back 65 days to May 29, 2021 (Figure 7a). Similarly, the winter 2021 outbreak had its origin on September 5, 2020. By superimposing these two outbreaks, the similarities between the two become apparent (Figure 7b).

At the beginning of both, the 7-day moving average of new diagnoses was 40 cases per 100K residents per week. Sixty-five days later, the rates for the winter 2020 and summer 2021 outbreaks were 220 and 195 cases per 100K residents per week, respectively. While these two curves may diverge, it would be prudent to assume they won’t unless we intervene to slow transmission. Unfortunately, we are squandering the efforts of the vaccinated and ignoring the sacrifices of the previously ill and dead, to party like it was 1999.

It is also important to point out that the data as presented here hide the heterogeneity that exists across counties (Figure 8a). Currently, Maricopa County is leading the pack with a case rate of 228 cases per 100K residents per week, while Pima County is experiencing 110 cases per 100K residents per week. Maybe a UA- alum should erect an opposing I-10 billboard from Phoenix to Tucson to keep score! If I were a Phoenician, I would be a bit worried as Maricopa County is well ahead of its fall/winter pace (Figure 8b).

Another way to compare the pace of outbreaks is to consider how many hospital and ICU beds were occupied at similar levels of transmission. The best comparison to where we are now (August 1, 2021) is November 5, 2020 and June 16, 2020. The 7-day moving average of daily new diagnoses were 2027, 2061, and 1960, respectively. The corresponding levels of hospital and ICU occupancy (not new admissions) on those dates is presented in Table 1.

In summary, current levels of hospital and ICU occupancy are similar to or slightly ahead of those of the winter 2021 outbreak (+38 and +68, respectively) but well below the levels seen in the summer 2020 outbreak (-353 and -149, respectively). Therefore, current community transmission is impacting hospitals similarly to how it did this past winter despite a high degree of vaccine update among those >65 years. Because herd immunity applies to populations not age groups, high vaccination rates among those >65 years doesn’t provide any protection to those who interact with unvaccinated adults who have much lower levels of vaccination. So, we should not hold a false sense of security that this outbreak will necessarily have less impact on our already overburdened hospital system.

The week ending January 17, 2021 remains Arizona’s deadliest with 1093 deaths (Figure 9). Weekly deaths now tally about 50 and are expected to rise with increased case rates, meaning in 3 – 4 weeks Arizona could be experiencing >100 deaths per week.

For the week ending July 25th, 1151 Pima County residents were diagnosed with Covid-19 (Figure 10). This is a 59% increase from the 722 cases initially reported last week.

New cases are being diagnosed at a rate of 110 cases per 100K residents per week. This rate is increasing by 39 cases per 100K residents per week. Pima County’s rates remain lower than the state average. Trends across the various age groups appear in Figure 11.