What To Know About COVID-19 Variants

Believed to be extremely transmissible, XBB.1.5 is an omicron subvariant and dominant strain
caronavirus mutation

A new omicron subvariant has been making headlines after becoming the dominant strain in the Northeastern United States as of early January.

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Known as XBB.1.5, according to the World Health Organization (WHO), this subvariant was detected in more than 38 countries between October 2022 and January 11, 2023. And according to the U.S. Centers for Disease Control and Prevention (CDC), as of January 28, XBB.1.5 was detected in 53% of all U.S. cases of COVID-19 and is estimated to be detected in 80% of all new cases in the U.S. by the end of February, making it the new dominant strain of COVID-19 in the U.S.

Will this mean we could be seeing another wave of coronavirus infections this year? It’s always a possibility, but as researchers continue to study the development of XBB.1.5, it’s important to understand how and why these subvariants continue to evolve beyond their original mutations.

Microbiologist and pathologist Daniel Rhoads, MD, explains how subvariants work and what the latest news could mean for potential future surges.

How many COVID-19 variants are there?

The CDC monitors all variants and subvariants of the original SARS-CoV-2 virus circulating in the U.S. The original virus has gone through several mutations since it was first detected in 2019 at the start of the COVID-19 pandemic. The CDC continues to monitor these variants, including up-and-coming variants of concern like XBB.1.5. Some of the variants tracked include:

  • Delta: Once the dominant variant in the U.K. and the U.S., it’s now no longer a “variant of concern.”
  • Omicron: This variant became a variant of concern when it was responsible for a global surge that began in November 2021. It and its subvariants are now responsible for nearly all cases of COVID-19 in the U.S.

According to the CDC, the omicron variant spreads faster and more easily than the original virus and the delta variant — and so far, that remains true as it continues to evolve with several subvariants that include XBB.1.5.

Latest subvariants

XBB.1.5 is a hybrid subvariant of the omicron strain of COVID-19 — meaning it carries combined characteristics from other omicron subvariants. And just like those other omicron subvariants, it does a good job of evading your body’s immune system. That’s why it’s currently the dominant strain in the U.S.

“XBB.1.5 is a subvariant that has emerged within the last year,” says Dr. Rhoads. “We don’t have much information yet, but it appears to be much like the same omicron subvariants that came before it. Even the symptoms are generally the same or similar, but the caveat is that the symptoms can look different in any one individual.”

That means you can be asymptomatic or have any number of symptoms that include:

  • Fever or chills.
  • Cough.
  • Shortness of breath or difficulty breathing.
  • Fatigue.
  • Muscle or body aches.
  • Headache.
  • New loss of taste or smell.
  • Sore throat.
  • Congestion or runny nose.
  • Nausea or vomiting.
  • Diarrhea.

How one person handles infection from XBB.1.5 may be entirely different from how someone else handles it, so it’s important to remain aware of any new symptoms you experience.

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How and why viruses mutate

Viruses are ever-changing in an effort to survive and spread. All viruses are made up of a bundle of genetic material (either DNA or RNA) that’s covered by a protective coating of proteins. Once a virus gets into your body — usually through your mouth or nose — it latches onto one of your cells. The virus’s DNA or RNA then enters your cell, where it can make copies of itself that go off and infect other cells. If the virus can copy itself and hijack enough of your cells without being wiped out by your immune system, that’s how you get sick.

With each new mutation that occurs in a virus, new characteristics arise. Some of these mutations cause the virus to stop working effectively, forcing it to die off or become less transmissible. Other mutations can cause the virus to become less detectable by our immune systems, become more transmissible or evade our immune system’s memory.

“I think of it like a dice roll: Every time somebody is infected, there are millions of new viral particles that are put out and there are some mistakes that can be made during the replication of the virus,” explains Dr. Rhoads. “Sometimes, these mistakes are actually helpful. But usually, they’re not.”

The CDC compares the mutation process to the branches of a tree: With each new mutation, a new branch grows, allowing the virus to grow in new directions. From those branches, there are stems, or subvariants, that are further mutations made on the backbone of the main variant. XBB.1.5, for example, is a mutation of the omicron “parent” virus.

“XBB.1.5 has a lot of mutations in its spike protein,” states Dr. Rhoads. “It’s thought that those mutations likely provide some immune escape, meaning if you have an underlying immunity due to vaccination or previous infection, this virus seems like it looks different enough that it can still cause infection.”

So, you can still get reinfected with this subvariant of COVID-19 even if you’ve had another strain of the virus.

Another way to think about variants, subvariants and virus lineages is thinking about a car.

“The original virus, SARS-CoV-2, is like the make of a car,” explains Dr. Rhoads. “Then, there are different models that come out that are a little bit different, even though it’s from the same designer and it’s basically the same thing. Omicron is a model of the original virus.”

And when you add special features to that unique make and model, you’ve got yourself a new subvariant.

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Will there be a surge in the fall or winter?

It’s hard to predict, but so far, a surge in cases, hospitalizations or deaths hasn’t been seen with this new variant. This may be due to a mix of factors, including the new variant itself, increased population immunity from vaccinations and prior infections and co-circulation of other respiratory viruses like influenza.

The CDC provides a helpful weekly update on current and emerging variants. As of February 18, 2023, XBB.1.5 is responsible for more than 80% of COVID-19 cases in the U.S., making it the current dominant variant. Those numbers only take into account the number of cases that have been reported, potentially leaving out a wide swath of cases that are overlooked thanks to the availability of at-home testing.

“Since home tests have become available, we’ve seen less demand for testing in the laboratory. The demand isn’t what it was six months ago,” says Dr. Rhoads. “So, it’s harder to recognize exactly what’s happening in the population because home tests may not be reported to anybody except their family.”

In short, as XBB.1.5 and future subvariants continue to appear, the potential for another surge is possible.

Does the vaccine protect against variants?

In the end, the shape-shifting nature of the coronavirus (and all viruses) is something that experts across the world are keeping a close eye on, but it’s not something you should expect to change the course of the pandemic overnight.

But the contagiousness of newer variants and subvariants is all the more reason to stay careful even as most states roll back social distancing guidelines. As of February 17, 2023, only 69% of U.S. adults are fully vaccinated, and only 16% have had an updated bivalent booster despite the CDC’s recent study that bivalent boosters are highly effective against XBB.1.5 and other omicron subvariants.

While breakthrough infections will occur and it’s possible to get reinfected, the number of cases that result in serious illnesses, hospitalizations or death is relatively low because vaccines are working to suppress the strength and spread of COVID-19. There are also new treatments for COVID-19.

“These new waves of infections show that the pandemic is not close to being over yet,” Dr. Rhoads notes. “At this time, vaccination has proven to be our most effective tool, and vaccines are readily available for many children and adults in the U.S. Vaccinations are our best defense against severe disease that can be caused by these emerging variants.”

What can you do to minimize infection?

The same protocols apply to XBB.1.5 that have applied to every other variant and subvariant of the coronavirus: The best preventive measures include getting vaccinated, wearing a mask during times of high transmission, staying 6 feet apart, washing hands often and avoiding people who are sick.

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