COVID-19 rates are on a steady rise in California. Has the fifth wave of virus begun?
A steady increase in coronavirus transmission has continued across most of California during April, recent state health data show, likely fueled by more contagious offshoots of the COVID-19 omicron variant that are gaining ground throughout the U.S.
California’s daily case rate is now 8.7 per 100,000 residents, with test positivity at 2.7%, the California Department of Public Health said in a Tuesday update. Each metric is up about 40% in the past two weeks.
CDPH last Friday reported positivity at 3.1% but in Tuesday’s update revised that day’s figure to 2.8%. It still marked the state’s highest measurement since Feb. 25, after falling as low as 1.2% in late March.
Wastewater monitoring data has shown potentially steeper increases in some well-populated parts of California.
The amount of virus detected in wastewater increased by about 192% in Davis between April 1 and April 17, and by about 140% in Sacramento in the same period, according to CDPH’s wastewater network data dashboard.
During the same stretch, Yolo County’s test positivity rate doubled and Sacramento County’s increased by about 50%.
There have also been significant increases in the Bay Area. Napa, San Francisco, Marin, Sonoma and Contra Costa counties all have test-positivity rates more than double the state average, ranging from 5.7% to 6.7%.
In San Jose, virus levels rose 150% in the wastewater from March 31 to April 16; test positivity spiked nearly 60% in the same stretch, CDPH infection numbers show.
Hospital numbers at the moment remain on a plateau. California on Tuesday reported 950 COVID-positive patients in hospital beds and has fluctuated between about 950 and 1,000 since April 15, state data show. The number of virus patients in intensive care units slid Tuesday to an all-time low of 112.
Both are tiny fractions of the omicron peak in early January, when California saw COVID-19 hospitalizations soar above 15,000 virus patients including 2,600 in ICUs.
Hospital trends throughout the pandemic have tended to lag behind case trends by a couple of weeks, though, meaning hospitalizations could begin to elevate soon given the increase in case rate. ICU numbers typically trail behind overall hospitalizations by an additional week or so.
BA.2 subvariants still on the rise
U.S. health officials have estimated that BA.2 is roughly 40% more transmissible than the original omicron variant, BA.1; and that a related strain called BA.2.12.1 is about 25% more transmissible than BA.2, which would make it about 75% more contagious than BA.2.
The U.S. Centers for Disease Control and Prevention in a weekly update Tuesday said the two subvariants combined for 97% of U.S. virus cases last week, up from 93% the prior week. Of sampled cases nationwide, 68% were BA.2 and 29% were BA.2.12.1, compared to 74% and 19% one week earlier, respectively.
For the CDC region that comprises California, Arizona, Nevada, Hawaii and Pacific island territories, BA.2 made up 82% and the more contagious BA.2.12.1 comprised 15% last week, shifting from 85% and 9%, respectively, the previous week.
The precise prevalence of the two subvariants in California is not yet clear because the CDPH data dashboard for variants does not distinguish between BA.1, BA.2 and BA.2.12.1. All three subvariants remain lumped together as “omicron,” which the state last week said made up 99% of recent specimens sequenced for variants.
One Sacramento-area testing network that does monitor for BA.2, the Healthy Davis Together project in Yolo County, reported BA.2 comprised 93% of positive cases for the week ending April 16, with the remaining 7% BA.1.
BA.2 has increased from 83% on April 9 and 68% on April 2 in Yolo County. The rate of Healthy Davis Together tests returning positive increased by just over double between April 2 and April 16, according to the project website.
Healthy Davis Together data does not yet distinguish BA.2 from BA.2.12.1.
Experts are still working to understand BA.2 and BA.2.12.1, especially the latter, and how they may influence factors like vaccine efficacy and immune protection from previous infection.
Health officials across the U.S. have said in recent weeks that it does not appear that BA.2 causes more severe illness than the original omicron variant.
Sacramento-area numbers by county
Sacramento County’s latest case rate is 6.2 per 100,000 residents, state health officials said in a Tuesday update, a 35% increase from one week earlier.
CDPH reported Sacramento’s test positivity rate at 3.2% as of Tuesday, up from 2.7% last week.
Hospitals in Sacramento County were treating 48 virus patients Monday, state data show, down from 55 one week earlier. The ICU total halved, to four from eight.
The CDC classifies Sacramento County in the “low” level of COVID-19 activity.
Placer County’s latest case rate is 5.2 per 100,000 residents, state health officials said in a Tuesday update, a 26% increase from one week earlier.
CDPH reported Placer’s test positivity rate at 3.7% as of Tuesday, up from 3.5% last week.
Hospitals in Placer County were treating 22 virus patients Monday, state data show, down from 33 one week earlier. The ICU total moved to four from three.
The CDC classifies Placer County in the “low” level of COVID-19 activity.
Yolo County’s latest case rate is 7.0 per 100,000 residents, state health officials said in a Tuesday update, a 9% increase from one week earlier.
CDPH reported Yolo’s test positivity rate at 1.5% as of Tuesday, up from 1.2% last week.
Hospitals in Yolo County were treating one virus patient Monday, state data show, compared to two one week earlier. The ICU total held at zero.
The CDC classifies Yolo County in the “low” level of COVID-19 activity.
El Dorado County’s latest case rate is 4.6 per 100,000 residents, state health officials said in a Tuesday update, a 35% increase from one week earlier.
CDPH reported El Dorado test positivity rate at 4.3% as of Tuesday, up from 2.4% last week.
Hospitals in El Dorado County were treating one virus patient Monday, state data show, compared to zero one week earlier. The ICU total held at zero.
The CDC classifies El Dorado County in the “low” level of COVID-19 activity.
Sutter County’s latest case rate is 3.2 per 100,000 residents and Yuba County’s is 5.0 per 100,000, state health officials said in a Tuesday update, respective increases of 17% and 100% in the past week.
CDPH reported Sutter at 3.3% test positivity, up from 2.4% last week. Yuba’s positivity was 3.1% as of Tuesday, up from 3% last week.
The only hospital in Yuba County, which serves the Yuba-Sutter bi-county area, was treating zero virus patients Monday, state data show, compared to two one week earlier. The ICU total decreased to zero from one.
The CDC classifies Sutter and Yuba counties in the “low” level of COVID-19 activity.
This story was originally published April 26, 2022 at 10:22 AM.
