The new, more contagious omicron subvariant is in Miami-Dade. Here’s what to know

A new, more contagious COVID omicron subvariant is quickly taking hold nationwide and has begun to circulate in Miami-Dade County.

Mutations in this new strain, XBB.1.5, enable the virus to spread more easily. The World Health Organization noted the subvariant is particularly adept at evading immunity from vaccination or infection, accounting for its rapid spread.

XBB.1.5 made up about 28 percent of U.S. COVID-19 cases, for the week ending Jan. 7, up from 2 percent in the beginning of December, according to the Centers for Disease Control and Prevention.

“What this variant is displaying is very similar to the previous waves of variants that we have seen since the beginning of the pandemic,” said Dr. David Andrews, associate professor of pathology at the University of Miami Miller School of Medicine.

Viruses are constantly mutating, and in the case of COVID, the mutations have led to waves of new cases over the course of the pandemic. The delta and omicron COVID variants have been particularly virulent.

In XBB.1.5’s case, its ability to evade immunity is giving it a “growth advantage” compared to the dozen other subvariants that have been recorded, and is pushing it to become the dominant subvariant, said Andrews.

What’s the dominant COVID variant in Miami-Dade?

Nomi Health, which operates the COVID test and vaccine sites in Miami-Dade County, said it began detecting XBB.1.5 in its COVID test samples in mid-December. So far, it makes up 2% of COVID test samples sequenced in the county, though the company expects to see a “significant increase” of samples linking to the new subvariant in the near future.

Medical experts rely on a variety of data, including COVID testing, wastewater samples and genetic sequencing to see how much COVID is spreading in the community and which variants are circulating.

Since mid-December, about 50% of COVID test samples from Nomi Health’s Miami-Dade sites were linked to BQ.1, which is the dominant strain in Miami-Dade and the rest of the country. The new subvariant, XBB.1.5, is the second most dominant in the country and is the third most dominant subvariant in the Southeast, according to the CDC’s latest Nowcast estimate.

The CDC estimates XBB.1.5 made up 17% of infections in Alabama, Florida, Georgia, Kentucky, Mississippi, North and South Carolina and Tennessee for the week ending Jan 7. BQ.1.1 makes up about 44% and BQ.1 about 20% in these states. The CDC does not break out the variants by states, only by regions of the country.

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What to expect with new subvariant

Both Pfizer and Moderna’s bivalent boosters were designed to provide some protection against the original COVID strain, as well as omicron. And since the subvariant is a descendant of omicron, the booster should provide some protection against it.

And while COVID cases and hospitalizations are expected to increase in the next few weeks as people return home from holiday gatherings and vacations, it’s “not going to be a wave like we saw a year ago or in the fall of 2021 with omicron and delta respectively,” said Thomas Hladish, an associate research scientist at the University of Florida who developed statistical forecasting models throughout the pandemic.

Instead, Hladish predicts the COVID situation will be closer to the summer wave, which in Florida saw most days with over 4,000 COVID hospitalizations. The most COVID hospitalizations were recorded on July 28, with 5,241.

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“But I am a little bit concerned because it seems to be infecting older people more than the summer 2022 wave,” he said. “And that tends to mean more severe outcomes.”

A variant doesn’t have to be more dangerous than other strains to cause severe disease in certain people, such as seniors, people who are immunocompromised or have preexisting medical conditions, he explained. Waning immunity and people’s behavioral changes over time, such as masking and social distancing, also play a role, he said.

This latest COVID wave has struck those 70 and over, according to the CDC data on U.S. COVID hospitalizations. Among those 70 and over, the rate of new COVID hospital admissions per 100,000 in the United States was 8.71 as of Jan. 9, the CDC says. For those 60-69, the hospital admissions rate was 2.70 and for those 50-59, the rate was 1.40 for this period.

By contrast, the rate of new COVID hospital admissions was 0.69 for people ages 30-39 and 0.51 for people ages 18-29, according to the CDC data.

“People’s behavior changes in response to the threat,” Hladish said.