Symptoms, Transmissibility, and More: What We Know About the BA.2 Subvariant

Experts say what happens in the next few weeks in the U.S. could be critical to whether or not the U.S. will follow in Europe's footsteps

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What is the BA.2 omicron subvariant and will it lead to another surge in the U.S.?

Experts say what happens in the next few weeks in the U.S. could be critical to whether or not the U.S. will follow in Europe's footsteps.



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As most COVID-19 restrictions are relaxed across Europe, including Austria, Britain, Denmark, Germany and France, the numbers of infections have inched higher in recent days. In the last two weeks, COVID-19 hospitalizations and deaths have both risen slightly in Britain.

The uptick is driven in part by BA.2 and by people largely abandoning masks and gathering in bigger groups.

So what is BA.2, what are the symptoms associated with it, where has it been detected and how contagious is it? Here's a breakdown.

What is BA.2?

BA.2, also known as "stealth omicron," is considered a subvariant of omicron.

BA.2 has several key mutations, with the most important of those occurring in the spike protein that studs the outside of the virus. Those mutations are shared with the original omicron, but BA.2 also has additional genetic changes not seen in the initial version.

So far, it has not yet been declared a variant of concern on its own. But that could change.

How contagious is BA.2?

According to several health experts, BA.2 appears to be more transmissible than omicron.

White House chief medical advisor Dr. Anthony Fauci said BA.2 is about 50% to 60% more transmissible than omicron, but it does not appear to be more severe.

"It does have increased transmission capability," Fauci said Sunday on ABC's "This Week." "However, when you look at the cases, they do not appear to be any more severe and they do not appear to evade immune responses either from vaccines or prior infections."

Northwestern University's Dr. Michael Angarone, an associate professor of medicine in infectious diseases, said the increased transmissibility could be particularly strong in close contacts of those infected, but it's still too early to tell.

"We're still trying to figure out why are we seeing this rising number of cases in some of these countries in Europe and that is because there's something markedly different about the virus," he said. "So is it more transmissible? Are more people going to become infected from one infected individual? There might be some markers of that."

How different is the BA.2 subvariant of the coronavirus? Not much, says NBC News medical contributor Dr. John Torres. The subvariant has not been labeled as a variant of concern, and it's not that different from Omicron, Torres says. Here's a metaphor: if a fully new variant is like the virus putting on a full new outfit, a subvariant is just putting on new shoes.

What are the symptoms of BA.2?

Medical experts say the symptoms for BA.2 are similar to those seen in many COVID infections.

These can include:

  • Fever or chills
  • Cough
  • Shortness of breath
  • Fatigue
  • Muscle or body aches
  • Headache
  • Loss of taste or smell
  • Sore throat
  • Congestion or runny nose
  • Nausea or vomiting
  • Diarrhea

But a Centers for Disease Control and Prevention report released late last year showed that omicron tended to cause the following symptoms:

  • Cough
  • Fatigue
  • Congestion
  • Runny nose

For some people, coronavirus causes mild or moderate symptoms that clear up in a couple weeks. For others, it may cause no symptoms at all. For some, the virus can cause more severe illness, including pneumonia and death.

Most vaccinated people either have no symptoms or exhibit very mild symptoms, according to health officials, and the virus rarely results in hospitalization or death for those individuals.

What's going on in Europe and China?

The rise in cases across Europe, from the U.K. and France to Italy and Austria, is being driven by several factors: The lifting of most — if not all — Covid restrictions, waning immunity from vaccines and booster shots, and the spread of the more transmissible omicron subvariant, BA.2.

Germany is seeing a surge in cases and has reported daily tallies of new infections of between 200,000 to 300,000 a day in the last week.

Europe is typically up to a month ahead of the U.S. in its COVID outbreaks.

Meanwhile, China is battling its worst COVID-19 outbreak since early 2020, with local governments pinning the blame on the BA.2 variant.

Mainland China has reported well over 1,000 new confirmed cases a day since March 12, with the number holding above 2,000 for the last three days. That's not including the asymptomatic case count, which can be just as many, or far more, than the number of daily confirmed cases.

Will BA.2 cause a surge in the U.S.?

Experts said they're watching closely, particularly as restrictions continue to lift across the U.S., but many say that even if a surge is seen, it likely won't be to the level seen earlier this year.

"I'm not expecting a big surge here, but we're gonna have to pay close attention and really be driven by data as we have throughout the whole pandemic," White House COVID-19 Response Coordinator Dr. Ashish Jha said last week.

Fauci also said he expects an increase in cases due to BA.2, but not necessarily a massive surge like other variants have caused.

"The bottom line is we'll likely see an uptick in cases, as we've seen in the European countries, particularly the U.K.," he said. "Hopefully we won't see a surge — I don't think we will."

Incoming White House COVID-19 Response Coordinator Dr. Ashish Jha talks about the new omicron sub-variant BA.2 and whether the U.S. will see the kind of surge that Europe and Asia are experiencing.

Do vaccinations work against BA.2?

Preliminary data indicate vaccinations and boosters are similarly effective in preventing symptomatic cases of BA.1, the original omicron variant, and BA.2.

Already, the makers of the two mRNA vaccines currently approved for use in the U.S. are seeking approval for a second booster shot for certain populations.

Drugmaker Moderna asked the Food and Drug Administration on Thursday to authorize a fourth shot of its COVID-19 vaccine as a booster dose for all adults.

The request is broader than rival pharmaceutical company Pfizer's request for the regulator to approve a booster shot for all seniors.

Is BA.2 in New England?

Stealth omicron had already been detected in New England earlier this year, and it's now the dominant strain in the region.

According to the CDC, the BA.2 variant, also known as "stealth omicron," now accounts for 55.4% of COVID cases in New England.

Boston Medical Center's Dr. Sabrina Assoumou said this week that while surges in cases are variable around the world, the U.S. should be prepared for any potential bump.

"We need to be preparing for the possibility of another surge," she said. "We just do not have as many people boosted in the state as we should. What we should do right now is focus on vaccinations and boosting as many people as possible."

Brigham and Women's Hospital's Chief of Infectious Disease Dr. Daniel Kuritzkes said the "big unknown" is how much omicron or vaccine immunity the population has to other variants.

Dr. Shira Doron of Tufts Medical Center said this spring could be similar to last year.

"If you look at this time last year, we saw cases begin to fall in January and then we saw a bump in March," she said. "Some people are predicting a bump not a spike over the next several weeks to months. One of the predictions is that the BA.2 variant could cause a bump but probably not a big spike because of the level of immunity we already have from omicron."

Assoumou said that as Massachusetts prepares for a potential bump, there should be an emphasis on testing.

"The key thing is to make sure we have an infrastructure that we can ramp up quickly if there is an increase in demand and cases," she said. "There is rapid testing available, but they are very costly. We can get tests from the federal government, but you only get a certain number so it is very important that we make sure that testing in a lot of places is widely available."

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