Nationwide, omicron subvariant BA.5 accounted for just 7.6 percent of COVID-19 cases in the U.S. as of June 4, according to the CDC's latest variant proportion estimates, but some Southwestern states are seeing higher proportions of cases involving the strain.
The strain is making larger week-by-week jumps than other variants that went on to become dominant, Deadline reports. The CDC estimates show its prevalence rose from 4.2 percent to 7.6 percent in one week, marking an 81 percent rise.
BA.5's prevalence is currently highest at 13.2 percent in HHS region 6, which includes Arkansas, Louisiana, New Mexico, Oklahoma and Texas, the CDC estimates show. The World Health Organization in April began monitoring "sister variants" BA.4 and BA.5. The latter was first identified in South Africa in February.
The highly contagious BA.2.12.1 omicron sublineage is still the dominant U.S. strain, accounting for an estimated 62.2 percent of cases for the week ending June 4. It's estimated to have a 25 percent growth advantage over BA.2, which is already more transmissible than the original omicron strain.
Some experts predict the BA.4 and BA.5 "sister variants" will outpace BA.2.12.1.
"BA.4/BA.5 has more immune evasiveness than BA.1.12.1, more transmissibility, and [is] more pathogenic in the lab and experimental model," Eric Topol, MD, founder and director of the Scripps Research Translational Institute in San Diego, said in a June 6 tweet, alongside data from the University of Minnesota Genomics Center. His tweet included an accompanying graph showing a steep rise in levels of BA.4 and BA.5 in wastewater samples from Minneapolis and St. Paul, Minn. Together, the variants accounted for a quarter of cases, based on the latest available data through May.
Dr. Topol said the graph based on Minnesota data "is where we are headed."
Two more updates:
1. COVID-19 hospitalizations may stabilize in June after climbing steadily since mid-April, CDC modeling suggests. Nationwide, admissions are projected to remain stable or have an uncertain trend in the next four weeks, with 1,200 to 10,900 new admissions likely reported June 24, according to the agency's ensemble forecast.
2. Northeastern states are seeing a drop in COVID-19 hospitalizations, a sign the latest wave is abating in the region, The New York Times reported June 7. Hospitalizations in Vermont have dropped more than 40 percent over the past two weeks. In Massachusetts, numbers have declined more than 20 percent. In Maine, Connecticut and New York, they've dropped about 10 percent.