The Cook County Department of Public Health on Aug. 23 reported that in Riverside and North Riverside, the number people testing positive for COVID-19 during the past week was higher than any week in three months.

 Riverside reported 12 new cases in the week ending Aug. 23, the most since the end of May, while North Riverside reported 11 new cases, the largest one-week total since May 11.

The increase in cases mirrors what officials are seeing nationwide, with the highly contagious delta variant of COVID-19 accounting for the majority of new cases. The county health department reported Monday that the delta variant accounted for 99.1 percent of new cases in the prior 14 days, a nearly 20-percent increase in that rate.

The county tracks variant spread through genomic sequencing, according to its online COVID-19 surveillance dashboard, and only a small number of COVID-19 positive specimens are sequenced. 

Since the pandemic began, the alpha variant still accounted for 61.7 percent of all COVID-19 specimens sequenced, the county reported Monday, but the delta variant cases are quickly catching up. 

In the prior 14 days, according to the county, the alpha variant accounted for zero new cases, while the delta variant accounted for 107 of 108 specimens sequenced in suburban Cook County.

The number of new cases in Brookfield in the past week was slightly lower as of Aug. 23, with 22 reported by the county. Within the past three weeks, however, Brookfield has seen 80 new cases. That’s nearly as many cases as Brookfield had recorded during the prior 13 weeks.

As elementary schools reopen their doors this week to full classrooms, local positivity rates are a mixed bag. In Brookfield, the seven-day rolling positivity rate as of Aug. 23 had dipped to 4.45 percent compared to the 14-day rolling rate of 5.11 percent.

In the 60546 ZIP code, which includes both Riverside and North Riverside, the seven-day rolling positivity rate was 6.68 as of Aug. 23, up from the 14-day rolling rate of 4.81.

As of Aug. 23, the Cook County Medical Examiner reported no new fatalities from COVID-19 in any of the villages covered by the Landmark.