Will COVID surge this spring? California sees a spike as new omicron strains hit US
As more contagious subvariants of the coronavirus emerge and begin to dominate new caseloads, and with restrictions loosening statewide and nationally, California has seen a steady increase of COVID-19 activity in recent weeks.
The California Department of Public Health on Tuesday reported a daily case rate of 6.9 per 100,000 residents, up 33% compared to three weeks earlier. The state’s test positivity has doubled to 2.6% from 1.3% since late March, as the pace of lab testing slows.
The latest numbers represent a small fraction of the peaks from winter’s omicron surge, during which California’s case rate soared from 20 to 300 per 100,000, and positivity rocketed from 3% to 23%, in less than a month.
But the metrics are now trending consistently upward for the first time since omicron first emerged in December, prompting some concern as to whether a fifth wave of the pandemic could soon arrive.
A family of new omicron subvariants makes up a fast-growing proportion of new cases and appear to be substantially more contagious than original omicron. Health officials are still working to determine if that means another surge is afoot, and if so, of what magnitude.
A weekly update Tuesday from the Centers for Disease Control and Prevention showed that two contagious omicron subvariants known as BA.2 and BA.2.12.1 combined for an estimated 93% of all U.S. virus cases for the week of April 10 to April 16, up from 79% two weeks earlier.
For the CDC region that includes California, Nevada, Arizona and Hawaii, BA.2 and BA.2.12.1 have increased to 94% from 80% in the past two weeks. Four weeks ago, they comprised only 42%.
The more transmissible of the two, BA.2.12.1, made up only 8.8% in the CDC region that includes California last week, compared to 52% for the region with New York and New Jersey.
But the new subvariant’s prevalence has more than quintupled in the Western region in the past two weeks, up from 1.7% on April 2. It took the subvariant four weeks to rise from 9% to more than half of cases in the New York-New Jersey region, CDC data show.
Hospital numbers tend to lag behind infection trends by at least a couple of weeks, meaning a spike in patients may emerge in the coming days or weeks.
California’s hospital numbers remained at a very low baseline Tuesday, with state health officials reporting 964 virus patients in hospital beds including 141 in intensive care units, California’s lowest ICU tally of any point in the pandemic.
What the numbers for new BA.2 subvariants mean
Health experts have recently estimated that the BA.2 strain is about 30% to 40% more contagious than the original omicron variant, BA.1.
The other emerging subvariant, BA.2.12.1, is quickly growing in prevalence in parts of the East Coast and has been determined as even more transmissible than BA.2.
In New York, state health officials last week announced the emergence of BA.2.12.1 and a closely related sublineage, BA.2.12, and said preliminary data point to the two subvariants being about 23% to 27% more transmissible than BA.2.
Coupled with the 30% to 40% boost from BA.2 over BA.1, that means experts believe BA.2.12.1 could be about 60% to 80% more contagious than the original omicron variant, which is already one of the most contagious viruses ever documented.
New York’s state health department in an April 13 news release said its “findings are the first reported instances of significant community spread due to the new subvariants (BA.2.12 and BA.2.12.1) in the United States.”
“At this time, there is no evidence of increased disease severity by these subvariants, though the Department is closely monitoring for any changes,” the statement from New York health officials continued.
The severity of a potential BA.2 and BA.2.12.1 surge in California will depend on how much immune protection residents have maintained from prior infection during the BA.1 surge, and how quickly that protection begins to fade. Health experts are still working to determine those factors, especially for the newer BA.2.12.1.
The exact prevalence in California is not yet clear for either new subvariant. CDPH maintains a data tracker showing the proportion of cases broken down by variant of concern but, as of a weekly update last Friday, it still did not distinguish between the various omicron subvariants including BA.1, BA.2 and BA.2.12.1, instead noting 100% of recent cases as omicron.
Health officials nationwide continue to say vaccines and boosters continue to give solid protection against infection and high efficacy against severe illness and death, even with the new subvariants.
COVID spiking in California wastewater
CDPH earlier this year launched a data dashboard tracking the levels of virus found in sewer water in several large California cities and metro areas. The data comes from multiple sources, including a Stanford-based research effort as well as a broader, nationwide wastewater surveillance network maintained by the CDC.
The latest wastewater readings tracked by CDPH show significant spikes in viral loads at some sites compared to early March, though they remain a sliver compared to peak levels from early January.
Wastewater data show virus levels have roughly tripled in the past month at a treatment plant serving the eastern half of San Francisco, more than doubled at a site in Orange County and spiked by close to 50% in Sacramento.
Gov. Gavin Newsom and state health leaders made wastewater surveillance a key tenet of the state’s “SMARTER” plan, sometimes referred to as California’s endemic plan for COVID-19.
In that plan, a spike discovered via wastewater surveillance is mentioned as a potential first trigger for further actions, such as deploying test supplies or arranging to send hospital surge staff to hard-hit regions.
The plan does not, however, give any specific numbers or thresholds for what would constitute the beginning of the surge and kick off those sorts of surge preparations.
Lagging booster rates and relaxed restrictions
The intensity of a BA.2 surge will also depend on vaccination and booster rates.
CDPH reports California recently surpassed a milestone: Just over 75% of residents 5 and older are now considered fully vaccinated against COVID-19, meaning they have had an initial series of the vaccines from Pfizer, Moderna or Johnson & Johnson, but not necessarily a booster dose. Another 9% of the eligible age group has had one dose of the two-dose mRNA vaccines from Pfizer or Moderna, meaning 84% are at least partially vaccinated.
But only 58% of Californians who are fully vaccinated and in the eligible time frame to receive a booster dose have been boosted, according to CDPH.
Additionally, many of California’s COVID-related restrictions have been dropped or significantly loosened in recent weeks.
After dropping the indoor mask mandate for the fully vaccinated in mid-February, state health officials ended the requirement for the unvaccinated on March 1. The state then dropped mandatory masking at K-12 campuses on March 12.
On April 1, CDPH ended a health order requiring businesses and venues to acquire proof of vaccination from attendees for indoor “mega” events with more than 1,000 people.
And on Monday, a federal judge in Florida overturned a CDC order mandating masks while on airplanes and other forms of public transportation. Major airlines and airports began to drop mask policies earlier this week.
Indoor masking is still required in California in several settings including hospitals, other health care settings, prisons, nursing homes, and emergency and homeless shelters.
This story was originally published April 19, 2022 at 4:21 PM.
