The new COVID-19 variant NB.1.8.1, which was linked to a large surge of hospitalizations in parts of Asia, could now make up more than 1 in 3 cases across the United States, the Centers for Disease Control and Prevention projected this week.

Last month, the CDC’s airport surveillance program had detected cases of the variant in arriving international travelers from several countries. The agency now says that nearly half of the COVID infections detected in that program the last week of May were the NB.1.8.1 variant.

The CDC cautioned that “precision in the most recent reporting period is low” for their estimates, meaning the projections carry a wide margin of error. Still, the estimated increase in prevalence in the U.S. highlights the variant’s high transmissibility — something experts had warned about as soon as it began spreading in this country.