In about a week, the prevalence of omicron subvariant XBB.1.5 grew more than 50 percent, according to the latest CDC variant proportion estimates.
The newest omicron relative gaining traction accounted for about 28 percent of cases for the week ending Jan. 7. Updated estimates indicate it has jumped to 43 percent of cases as of Jan. 13.
"XBB.1.5 is no slouch. It is outcompeting a soup of new omicron variants that have arisen in recent months," Eric Topol, MD, founder and director of Scripps Research Translational Institute in San Diego, wrote in a Jan. 8 op-ed for The Washington Post.
Three more COVID-19 updates:
1. COVID-19 hospitalizations are at their highest levels since March. An average of 45,600 patients were hospitalized as of Jan. 12, up 9 percent over the last two weeks, according to HHS data tracked by The New York Times. Overall, COVID-19 hospitalizations are far lower than levels seen during the height of last winter's omicron surge, when the U.S. was reporting more than 150,000 daily hospitalizations. Still, hospitals are under significant capacity strain amid ongoing staffing shortages and an early and severe start to the respiratory virus season.
2. The World Health Organization updated its mask guidance on Jan. 13 to recommend their use "irrespective of the local epidemiological situation." The WHO recommends masks after a recent exposure to someone with COVID-19; when someone has or suspects they are infected; when someone is at high risk of severe disease; and for anyone in crowded or poorly ventilated settings. The WHO also included updated guidelines on reduced isolation periods for COVID-19 patients and extended its recommendation of the Paxlovid antiviral regimen for those with mild to moderate disease.
3. XBB.1.5 does not differ enough from other omicron sublineates to warrant its own Greek letter name, WHO officials said Jan. 11. Available data suggests it is behaving similarly to other subvariants in terms of transmissibility, severity, immune escape and its effect on interventions. When and if that changes as more data becomes available, "We're not afraid to use these Greek letters or to assign different subvariants," Maria Van Kerkhove, PhD, the WHO's technical lead on COVID-19, said.