An infectious diseases expert on Sunday warned that the new strain of the Omicron Covid-19 subvariant known as "XBB" may already be in the country.

Dr. Rontgene Solante, chief of the Adult Infectious Diseases and Tropical Medicine Unit of the San Lazaro Hospital in Manila, said the subvariant's possible entry may be due to eased border restrictions.

"We cannot rule that out because first of all, the samples we are testing now for sequencing are not that many anymore. Second, we have an open border," Solante said.

"There's a possibility that this variant can also be present here, but we don't know. We don't know yet because it hasn't been detected yet by the Philippine Genome Center," he added.

The Department of Health previously said that the Omicron subvariant, which is believed to be the cause of the recent spike in Covid-19 cases in Singapore, has not yet been detected in the country.

"As of 13 October, we have not detected the said variant in the Philippines," the DoH said referring to XBB, a recombinant of BJ.1 (BA.2.10.1 sublineage) and BM.1.1.1 (BA.2.75 sublineage).

Preliminary studies suggest that the sublineage shows higher immune evasion ability than BA.5, according to the Health department.