Is the Omicron Subvariant XBB.1.5 Really More Contagious Than Other Variants?
Public health officials are buzzing about a new COVID-19 variant that’s suddenly causing a wave of infections in the U.S. XBB.1.5 has more than doubled the amount of COVID-19 cases it caused each week for the last four weeks, shooting up from causing 4% to 41% of new infections in December, according to the Centers for Disease Control and Prevention’s COVID-19 variant tracker.
XBB.1.5 seemingly came out of nowhere, snatching the title of the most common COVID-19 subvariant in the U.S. from BA.5, BQ.1, and BQ.1.1, which have caused the majority of cases in the country since early fall. White House COVID-19 response coordinator Ashish Jha, M.D., M.P.H., called this a “stunning increase” on Twitter, before noting that public health experts “don’t know” if it’s more dangerous than previous forms of the virus.
So, what’s the deal with XBB.1.5 and how can it potentially impact the rest of your winter? Here’s what you need to know.
What is XBB.1.5?
XBB.1.5 is a subvariant of Omicron, explains Thomas Russo, M.D., chief of infectious diseases at the University at Buffalo in New York. It’s an off-shoot of XBB, which is a hybrid version of two strains of the BA.2 form of Omicron, says Amesh A. Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security.
“It has become more dominant and even has further evolved to become more transmissible,” Dr. Adalja says, noting that it’s shown up more often in places like Singapore and the Northeastern U.S.
How contagious is it?
Experts agree that XBB.1.5 is very contagious—and possibly the most contagious form of COVID-19 yet. “It’s outcompeting the other variants at a fast pace and that’s resulting in widespread spread right now,” says William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine.
Because XBB.1.5 is so contagious, “it’s just simple Darwinian forces that are allowing it to displace other versions of Omicron,” Dr. Adalja says.
XBB.1.5 has a mutation that allows it to bind tightly to the ACE receptor of cells, which can increase its contagiousness, Dr. Russo says. “There’s no question that it’s extraordinarily infectious,” he adds.
As for whether XBB.1.5 is more dangerous, it’s not entirely clear at this point. However, data from Singapore suggests that hospitalizations don’t jump up when XBB.1.5 is heavily circulating and “lab studies indicate that our current vaccines continue to provide protection against severe disease,” Dr. Schaffner says.
XBB.1.5 symptoms
As of now, it doesn’t seem that XBB.1.5 is causing different symptoms from other more recent strains of COVID-19, Dr. Schaffner says. As a refresher, the CDC’s official list of symptoms includes:
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
Worth noting: The ZOE Health Study, which is a research project from scientists at Massachusetts General Hospital, the Harvard T.H. Chan School of Public Health, King’s College London, Stanford University School of Medicine and the health app ZOE, recently reported that these are the most common symptoms of COVID-19:
Sore throat
Runny nose
Blocked nose
Sneezing
A cough without phlegm (aka dry cough)
Headache
A cough with phlegm (aka wet cough)
Hoarse voice
Muscle aches and pains
Altered sense of smell
XBB.1.5 side effects and treatment
As of right now, XBB.1.5 doesn’t seem more likely to cause long COVID than other forms of the virus. However, Dr. Schaffner points out, there is always a risk of developing long COVID after you have the virus.
Treatments for vulnerable people who happen to get the virus are a little different than they’ve been in the past, though. Dr. Russo points out that monoclonal antibody treatments and Evusheld, which is designed to lower the risk of developing severe COVID if you get sick “are all ineffective against XBB.”
However, antiviral medications like Paxlovid are still thought to work, Dr. Russo says.
Overall, Dr. Schaffner recommends making sure that you’re up to date on your COVID-19 vaccines, and considering masking up in public again, particularly when you go to places like the grocery store.
“The waves of RSV and the flu may have pushed back a wave of COVID cases,” Dr. Russo says. “This will hopefully be muted compared to last winter when Omicron first showed up, but we will have to wait and see.”
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