The fast-spreading COVID-19 omicron variant has rocketed to dominance over the highly contagious delta strain across much of the U.S., jumping from less than 13% of sequenced cases on Dec. 11 to more than 73% in a week’s time, the Centers for Disease Control and Prevention reported Monday.
It was unclear how fast omicron has spread in California — the California Department of Public Health had not updated its variant tracking data and had no immediate comment Monday. But the rapid spread across the rest of the country alarmed infectious disease experts.
“Amazing — this is faster than I expected,” said Dr. John Swartzberg, clinical professor emeritus of infectious diseases and vaccinology at UC Berkeley’s School of Public Health. “I think this is fair to say: This is explosive.”
In the Bay Area, where the first U.S. omicron variant case was reported Dec. 1 in a vaccinated San Francisco resident who had recently returned from South Africa, followed two days later by six cases in Alameda County and one case in Santa Clara County a week later, health officials have been bracing for a surge of infections and urging residents to get booster shots.
Contra Costa County reported its first cases of the variant Monday — three residents, two of whom were fully vaccinated, though none had yet gotten a booster shot. None have been hospitalized so far.
“We knew it was just a matter of time before the omicron variant appeared in Contra Costa County,” said county health Officer Dr. Chris Farnitano in a statement. “We’ve been encouraging anyone who is eligible to get a booster dose of the Pfizer or Moderna vaccine to do so. With today’s news and the holidays just around the corner, that message is even more important. People who get the booster are far less likely to get gravely ill or be hospitalized. That’s our wish for this holiday season.”
Omcron’s rapid spread in South Africa last month alarmed health officials around the world, prompting the World Health Organization to declare omicron a “variant of concern” on Nov. 26. On Monday, the WHO’s director general urged people to cancel holiday gatherings to slow its spread.
“There is now consistent evidence that omicron is spreading significantly faster than the delta variant,” Director General Tedros Adhanom Ghebreyesus said. “There can be no doubt that increased social mixing over the holiday period in many countries will lead to increased cases, overwhelmed health systems and more deaths. … It’s better to cancel now and celebrate later than to celebrate now and grieve later.”
CDC Director Dr. Rochelle Walensky said Dec. 14 that the omicron variant was at “about 3% across the nation” and was “rapidly increasing,” gaining ground on the highly transmissible delta variant that has been dominant since June and drove outbreaks throughout the U.S. over the summer and fall. The agency has since revised its numbers upward for the week of Dec. 11 to 12.6%. The variant has grown fastest in New York and other East Coast states, the Midwest, Great Lakes and the Northwest regions.
CDC data show the omicron variant spread from 0.7% of U.S. cases Dec. 4 to 12.6% by Dec. 11 and 73.2% by Dec. 18. It took delta more than a month to reach that level of dominance across the country.
In California, Department of Public Health data show the delta variant began gaining ground in April. Two months later delta had accounted for less than half of sequenced samples. But just a month after that in July, delta accounted for 93% of cases, peaking at 99.5% last month. As of Dec. 15, delta accounted for 98.6% and omicron, at 49 total cases, 1.4% of samples sequenced in the state.
Swartzberg said omicron is proving to be about five times more transmissible than the delta variant, which itself was more transmissible than earlier variants, and that “it’s hard to imagine” its trajectory in California won’t be similar to its rapid growth nationally.
Health experts across the country urged people to get vaccine booster shots to bolster their immunity. The CDC earlier this month authorized booster shots for everyone age 16 and older.
Dr. Ashish K. Jha, dean of the Brown University School of Public Health, said Monday on Twitter that “omicron is now essentially everywhere.”
“This has become dominant so fast,” Jha said. “Get you booster. Wear a mask in large indoor events. Use rapid tests before gathering. We can get through this, people.”
Much still is unknown about how virulent the omicron variant will prove to be, with some data and reports suggesting a milder illness and short-lived spikes in infection.
Dr. George Rutherford, an infectious disease specialist at the University of California-San Francisco, said figures out of the United Kingdom suggest relatively few hospitalizations and deaths from omicron so far. If the new variant produces milder illness, then seeing it outcompete the deadly delta variant would be a blessing, he said.
Rutherford also noted that data from overseas suggests a short, sharp upturn in cases before the omicron infection wave starts to crash, which also would be merciful.
Swartzberg said a recent study out of Hong Kong indicated that while omicron more easily infected the upper respiratory system, it was less active in the lower respiratory system, where more serious disease is likely to result.
“A upper respiratory disease is a cold — we can live with that,” Swartzberg said. But he added that “flies in the face of” a recent Imperial College London study that found omicron to be no less dangerous than delta. “So we’ll have to wait and see about that.”
Source: www.mercurynews.com