Wastewater Surveillance Shows Plateauing in Viral Concentrations

With more individuals using over-the-counter or OTC tests to assess COVID-19 infections, the county COVID-19 case rate, which doesn’t include the results from OTC tests, may underestimate the level of transmission. Fortunately, Public Health is able to utilize wastewater surveillance to detect significant changes in viral loads or new variants.

Presently, there are four wastewater treatment plants that perform viral surveillance for SARS-CoV-2.

The two largest plants are the Hyperion Water Reclamation Plant and the Joint Water Pollution Control Plant, serving about 7.5 million LA County residents across most of the county.  At the Hyperion Plant, although viral concentrations declined notably in the first half of September, there was a small increase this past week. The Joint Water Pollution Control Plant reported small decreases throughout September.

The two smaller plants, the Lancaster Water Reclamation Plant that serves Lancaster and Palmdale, and the Tapia Water Reclamation Facility, serving Calabasas and surrounding areas, reported stable concentrations with small increases the past few days.

While the plateauing in viral concentrations in wastewater may signify that viral transmission is no longer decreasing, because most of the other early alert signals indicate low concern, Public Health reported being hopeful that transmission is not increasing at this time. However, the plateauing does highlight the need to carefully monitor the other signals to see if there are any additional signs in the next couple of weeks that suggest changes in transmission patterns or illness severity. 

Overall, the county continues to report improved COVID-19 metrics. The 7-day average case count in the county is 1,297, an 8% decline from one week ago when the 7-day average of 1,397 cases was reported.

Over the past seven days, the average number of daily COVID-positive patients in LA County hospitals was 499, a 17% decline from one week ago when the average number of daily COVID-positive patients per day was 602.

Deaths, which typically lag hospitalizations by several weeks, remained stable at an average of 11 deaths reported each day this past week, nearly the same as an average of 12 daily reported deaths a week ago. The 7-day average test positivity rate remains stable at 4.3% over the past week.

The Omicron variant continues to account for 100% of Los Angeles County sequenced specimens, and the BA.5 subvariant of Omicron, remains the predominant subvariant. 

Details: http://www.publichealth.lacounty.gov