Tokyo: Concerns are mounting that the highly infectious XBB.1.5 omicron variant of the novel coronavirus may spread in Japan, where COVID-19 daily fatalities are staying high.

XBB.1.5, called kraken by some, is spreading rapidly in the United States. The variant accounted for 49.1 pct of new infections over the week to Saturday, up 4.3-fold from a month before, according to the U.S. Centers for Disease Control and Prevention.

In Japan, XBB.1.5 cases have been reported in Tokyo and the western city of Kobe.

XBB.1.5 is an offshoot of XBB, which resulted from a recombination of two BA.2 omicron variants. It may have a stronger ability to escape acquired immunity.

The new variant may “contribute to an increase in cases globally,” the World Health Organization has said.

According to Kyoto University professor Hiroshi Nishiura, XBB.1.5 is believed to have an effective reproduction number, or the average number of people a single carrier infects, 1.47 times that of the currently prevailing BA.5 omicron variant.

“Infections in Japan are on the decline, but there is the risk that XBB.1.5 may start a new infection spike,” Nishiura said.

The new variant is feared to spread in Japan after the country drastically eased its COVID-19 border control measures last autumn.

“XBB.1.5 can attach itself to human cells more easily, and its infectiousness therefore may be stronger than that of previous variants,” Tokyo Medical University professor Atsuo Hamada said. “We need to perform genomic analysis and monitor how it may affect the current eighth wave of infections.”

He stressed the importance of basic precautions, including inoculations, washing hands and gargling.

JIJI Press