A new omicron subvariant — XBB.1.5 — is on Hawaii’s radar as the new year gets underway.

The subvariant, which some scientists have nicknamed the “Kraken” due to its formidable growth advantage, has been detected in Honolulu County wastewater samples, potentially bringing another rise in COVID-19 cases and hospitalizations in the state.

On Wednesday the World Health Organization released a risk assessment of XBB.1.5, noting its rapid increase in the Northeast U.S., and evidence of a growth advantage likely to lead to global predominance.

Omicron subvariant XBB.1.5, first detected in New York, is a descendent of XBB — a recombinant of two BA.2 sublineages that drove up cases in Singapore. WHO has received XBB.1.5 sequences from 38 countries.

There is no data, however, on the severity of XBB.1.5, WHO said, and it does not carry any mutation known to be associated with potential changes in severity.

WHO noted, however, that its confidence was limited because it only has data from one country — the U.S.

Tim Brown, an infectious disease expert at the East-West Center in Manoa, expects another rise in infections and hospitalizations in Hawaii in coming weeks due to the new subvariant if it grows the way it has in the rest of the country.

“I do think we’re going to see an XBB.1.5 wave that’s going to occur probably across the United States,” Brown said during a recent “Spotlight Hawaii” conversation. “Now, exactly how high it will be, we don’t know yet. It may be as high as the BA.5 wave we had earlier this year, it may not be. It may be lower.”

XBB.1.5 now represents three-quarters of all infections in the Northeast, he noted, where hospitalizations among elderly have increased, particularly those ages 70 and older.

Brown said COVID-19 transmission was up in Hawaii over the holidays, even though new case counts appeared stable, when taking positivity rates into account.

A drop in the number of daily tests conducted will result in lower case counts, he said. To get a clearer picture, he looked at positivity rates, or percentage of tests that are positive, SARS-CoV-2 virus concentrations in wastewater, and hospitalizations.

On Wednesday, the state Department of Health reported the state’s seven-day average of new COVID-19 cases at 170 compared with 177 on Jan. 4. The state’s average positivity rate declined slightly to 7.5% compared with 7.9% the previous week.

Hospitalizations, however, have shown an uptick in COVID-19 patients compared with December.

On Wednesday the seven-­day average of COVID-19 patients in hospitals per day was at 88 for the past week compared with 81 the previous week, according to the Healthcare Association of Hawaii. During the week before Christmas, the average was at 60 patients per day.

The latest wastewater report also noted higher concentrations of SARS-CoV-2, the virus that causes COVID-19, in wastewater samples.

Higher concentrations of the virus in wastewater can be an early indicator for an increase in cases because infected people begin shedding virus in their feces two to three days before the onset of symptoms.

Health officials continue to recommend that those eligible get the new bivalent booster for protection against hospitalizations and death from COVID-19.

More studies are emerging that find the bivalent has a better neutralizing antibody response to BA.5 as hoped and anticipated, according to Eric Topol, professor of molecular medicine at Scripps Research, as well as against XBB.

These studies include five live virus studies, which he considers a more reliable assessment, and which “offer consistent evidence of broadened immunity from the BA.5 vaccine that is improved over the original booster shots.”

To date, a total of 267,603 Hawaii residents, or 24% of the state’s eligible population, have received the bivalent booster, according to DOH.

The White House on Wednesday also announced it would extend the COVID- 19 public health emergency through April, according to CNBC, due to concerns over XBB.1.5. The U.S. Department of Health and Human Services must renew the emergency every 90 days to maintain certain health care flexibilities, and has done so since January 2020.

DOH also reported five more deaths, bringing the state’s COVID-19 death toll to 1,770.