The omicron subvariant XBB.1.5, dubbed by some officials as the most formidable yet due to its growth advantage, has been detected in Honolulu County wastewater samples.

The Hawaii Department of Health’s most recent wastewater surveillance report documents higher concentrations of the virus that causes COVID-19 as well as the arrival of the XBB.1.5 subvariant.

Higher concentrations in wastewater can be an early indicator that the number of COVID-19 infections is increasing, said DOH, because infected people begin shedding virus in their feces two to three days before the onset of symptoms.

“The wastewater data is concerning, but not alarming,” said State Epidemiologist Dr. Sarah Kemble in a newsletter. “The detection of higher virus concentrations means we should closely monitor case counts and hospitalizations for a possible surge in cases and be ready to respond should a surge materialize.”

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The wastewater report found omicron subvariants BA.5, BQ.1 and BQ.1.1 to have the highest relative abundance across all four major counties, followed by BA.2, XBB, BF.11 and others.

The report said XBB.1.5 has not been detected in clinical samples across the state, but was found in Honolulu County wastewater.

Today, the Centers for Disease Control and Prevention updated its Nowcast model for variants in the U.S., and lowered the proportion of XBB.1.5 in new cases to 28%, down from 40.5% last week.

The U.S. Food and Drug Administration today also issued a notice warning that it does not anticipate that Evusheld will neutralize XBB.1.5 for those who are immunocompromised.

“This means that Evusheld may not provide protection against developing COVID-19 for individuals who have received Evusheld and are later exposed to XBB.1.5.,” said the FDA in a statement. “However, we are awaiting additional data to verify that Evusheld is not active against XBB.1.5. We will provide further updates as new information becomes available.”