US COVID markers rise; XBB.1.5 keeps fast pace

COVID swabbing

US Army National Guard, Kevin Torres Figueroa / Flickr cc

Most of the nation's COVID-19 indicators are on the rise after the holidays, with the Omicron XBB.1.5 subvariant spreading quickly, the US Centers for Disease Control and Prevention (CDC) said today in its weekly data summary.

Over the past few weeks, COVID-19 activity in the United States and other nations has been fluctuating due to holiday-related impacts such as delays in reporting. However, global health officials continue their close watch of XBB.1.5—thought to be the most transmissible subvariant so far—that was first identified in the eastern United States in October.

US metrics all on the upswing

In CDC tracking of infections as of Jan 4, the 7-day average for new daily cases is 67,243, up 16.2% compared to the previous 7-day average. Over the same period, the 7-day average for new hospital admission rose 16.1%, and deaths increased 8.3%. Likewise, test positivity is increasing and is at 16%.

Also, the number of locations in the high–COVID-19 community transmission level increased by 10.6%. Overall, 49 of 52 jurisdictions were in the high- or medium-level community ranges, for which the CDC recommends measures such as wearing a high-quality mask or respirator in indoor public spaces and screening in high-risk settings.

Regarding wastewater surveillance, the CDC said about 80% of sites across the country are reporting moderate to high SARS-CoV-2 levels, with 58% recording their highest levels since December 2021.

CDC fine tunes XBB.1.5 proportion estimates

Last week, the CDC in its Nowcast variant proportion estimated that XBB.1.5 made up 41% of sequenced samples. In a new estimate today, it scaled that back to 18%. In its weekly data report, it said that last week's numbers were based on Nowcast estimates, a method it uses to predict variant proportions before more precise weighted estimates are available.

Since last week's projections, the CDC has more data from mid-December and other data that were delayed over the holidays, which led to the scaled back but more certain estimate of 18% for XBB.1.5 on Dec 31.

For this week, the Nowcast prediction for XBB.1.5 is 26%, with a range of 14% to 47%. "These findings demonstrate that XBB.1.5 is spreading quickly," the CDC said, noting that the subvariant is dominant in two regions of the northeast. At the national level, BQ.1 and BQ.1.1 make up an estimated 55.8% of sequenced samples.

On Twitter this week, Ashish Jha, MD, MPH, White House COVID-19 coordinator, said many factors will impact whether the United States will have a XBB.1.5 wave, and if so, how big it will be. They include population immunity and people's actions. He recommended that people get up to date on their COVID-19 boosters, test before attending large gatherings or seeing vulnerable people, wear a high-quality mask in crowded indoor spaces, and improve indoor ventilation.

Jha urged people with symptoms to get tested right away and, if positive, get evaluated for treatment.

In a related development, the National Institutes of Health (NIH) yesterday announced that it will pilot a home-based test-to-treat program starting in Berks County, Pennsylvania, with up to 8,000 eligible participants. The results of the pilot will be used to launch the program on a larger scale to include about 100,000 people across the United States.

Telehealth provider eMED will implement the program, hosting a test-to-treat website where participants can enroll, report symptoms, and receive telehealth and antiviral treatment delivery. The program was first announced by the White House in September 2022.

XBB.1.5 growth advantage, uncertain impact for Europe

In a variant update yesterday, the European Centre for Disease Control and Prevention (ECDC) said XBB.1.5 is estimated to have a large growth advantage over previously circulating lineages in the United States (139%) and Europe (137%), though it included a caveat that the estimates are uncertain.

The ECDC said it's not certain that XBB.1.5 will become dominant in the European region, because North America and Europe have seen differences in variant circulation several times during the pandemic.

It said the growth advantage is likely due to already high levels of immune escape, combined with a mutation in the spike that could give the subvariant a transmissibility advantage, more immune escape, or both. Currently, there are not enough data to assess changes in disease severity.

XBB.1.5 could fuel increases in Europe, but probably not in January, due to very low levels of the subvariant in the region, the ECDC said.

Earlier this week, World Health Organization (WHO) officials said its variant advisory group is assessing the XBB.1.5 developments and will soon weigh in on the assessment.

This week's top reads