Most reported Covid-19 deaths in the U.S. are still from the delta variant, not omicron, Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said Wednesday.
Covid deaths, based on a seven-day moving average, have reached 1,600 per day in the U.S., a 40 percent increase over the previous week, according to CDC data.
Full coverage of the Covid-19 pandemic
Walensky, speaking at a White House Covid-19 Response Team briefing, said she expects most of those fatalities are still lagging deaths from the delta variant wave.
The omicron variant only recently became the dominant strain in the U.S., surpassing delta around mid-December. The new strain now accounts for an estimated 98.3 percent of all new cases, according to CDC data.
Public health officials will monitor "deaths over the next several weeks to see the impact of omicron on mortality," Walenksy said during the briefing. "Given the sheer number of cases, we may see deaths from omicron, but I suspect the deaths we're seeing now are still from delta."
Omicron causes less severe disease
Walensky's comments came a day after researchers released a new study based on data from Kaiser Permanente Southern California that found the omicron variant appears to cause less severe disease than previous strains and shorter hospital stays.
The study, which was posted online to a preprint server and hasn't been peer-reviewed yet, looked at nearly 70,000 Covid patients in California, the majority of whom had illness caused by the omicron variant.
Walensky cited the study at the Wednesday briefing, saying it remains consistent with data from South Africa and the United Kingdom and provides some understanding of what the U.S. can expect in coming weeks.
"The risk of hospitalization remains low — especially among people who are up to date on their Covid vaccines," Walensky said. "However, the staggering rise in cases, over 1 million new cases each day, has led to a high number of total hospitalizations."
Masks provide different levels of protection
While omicron may be less severe, "the sudden and steep rise in cases due to omicron is resulting in unprecedented daily case counts, sickness, absenteeism and strains on our health care system," she said.
The CDC is encouraging all Americans to wear well-fitted masks to protect themselves and others against the new strain.
She said the agency is preparing an update to its website on masks, noting that different masks and provide different levels of protection.
Follow NBC HEALTH on Twitter & Facebook.
