What is the BA.2 omicron subvariant and will it lead to another surge in the U.S.? Dr. Michael Angarone, the associate professor of medicine in infectious diseases at Northwestern Medicine, weighs in.
News about the BA.2 omicron subvariant continues to grow as it becomes the dominant COVID strain not just in the Midwest but across the U.S., but what should you be watching for?
Chicago's health department said it is monitoring a "slight increase" in cases as BA.2 now represents more than 50% of Midwest COVID cases, according to estimates from the Centers for Disease Control and Prevention.
Chicago's top doctor had already said BA.2 would likely make up a majority of the city's cases by the end of the month, a transition health officials are watching closely.
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 as several countries report outbreaks similar to levels seen during Chicago's omicron surge in January.
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.
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"BA.2 is part of omicron," Dr. Isaac Ghinai, medical director for lab-based surveillance at the Chicago Department of Public Health, said Thursday. "Omicron is a variant of concern, therefore BA.2 is a variant of concern. Same as BA.1 is a variant of concern."
But that could change.
"People are looking very closely at whether or not BA.2 needs to be classified separately and monitored separately," Ghinai said. "But even without that it is a variant of concern, it's being monitored very closely at the local levels, at the state levels and at the national levels."
How contagious is BA.2?
According to several health experts, BA.2 appears to be more transmissible than omicron.
"There's four unique mutations in the spike protein that are distinct in BA.2, and different from BA.1. ... It seems that these mutations will propel the transmissibility to about a 30% to 50% higher degree of contagiousness than the BA.1 variant," said Dr. Gregory Huhn, an infectious disease physician and the COVID-19 vaccine coordinator for Cook County Health.
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'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."
What are the symptoms of BA.2?
According to Angarone, the symptoms for BA.2 are similar to those seen in many COVID infections.
"So this is the same virus, so SARS Coronavirus 2, so we're seeing the same symptoms," he said.
Huhn noted that while omicron led to more upper respiratory symptoms, it remains too early to tell if BA.2 will continue that trend.
"I don't know if we, right now, know the particular features that are distinct for BA.2 versus BA.1. I mean, for BA.1, we knew that it was mostly an upper respiratory-type infection rather than the lower respiratory infections that can lead toward pneumonia and further and greater complications," he said.
Still, NBC News reported symptoms associated with BA.2 seem to largely mirror a small number of symptoms commonly reported in omicron infections. Those include:
- Cough
- Fatigue
- Congestion
- Runny Nose
Anecdotal reports have suggested that dizziness could be a possible symptom, but they are so far unfounded.
"We will have to wait and see what exactly that means," said Dr. Rachael Lee, an associate professor of infectious disease and a health care epidemiologist at the University of Alabama at Birmingham. Infections in general can cause dizziness if people become dehydrated, she said.
"When we are sick and our body is taking care of the infection, we can get things like fever," Lee said. "If you have fever, in particular, and if you're sweating a lot, you're losing a lot of fluid."
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.
Still, omicron presented a shift in common symptoms for many.
Dr. Katherine Poehling, an infectious disease specialist and member of the Advisory Committee on Immunization Practices, told NBC News in January that a cough, congestion, runny nose and fatigue appear to be prominent symptoms with the omicron variant.
But unlike the delta variant, many patients were not losing their taste or smell. She noted that these symptoms may only reflect certain populations.
The symptoms COVID infections, according to the CDC, 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
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 uptick in cases" due to BA.2, but not necessarily a massive surge like other variants have caused.
"This is different than the switch from delta to omicron. That truly was a much more drastic change in the virus and that's where we really saw transmissibility increase magnitudes above delta," Huhn said. "This is more of a slight variation and so we're not seeing the transmissibility really accelerate as we did when we switched from delta to omicron."
Ghinai said he doesn't believe BA.2 will lead to a surge like the one previously seen during the omicron peak, but changes are expected "at some point."
"We're at a nearly historic low in terms of COVID here in Chicago, it's very likely that there may be some changes in transmission," he said. "I don't expect it to be a surge like we saw the last few months because of omicron, because of delta."
Huhn said experts will be closely watching as restrictions continue to loosen and some booster immunity may start to wane.
"Now that we've rolled back, you know, we'll see again in the next few weeks if there will be an uptick in cases," he said.
Where has BA.2 been detected?
As most COVID-19 restrictions are relaxed across Europe, including Austria, Britain, Denmark, Germany and France, the numbers of infections have inched higher. Earlier this month, COVID-19 hospitalizations and deaths both rose slightly in Britain.
The uptick was driven in part by BA.2 and by people largely abandoning masks and gathering in bigger groups.
According to new estimates released Tuesday by the CDC, the BA.2 subvariant of COVID-19, otherwise known as “stealth omicron,” is now the dominant strain of the virus in the Midwest and in the United States.
The data, released Tuesday, reflects estimates of COVID cases diagnosed between March 19 and March 26, according to the CDC’s website.
Those estimates peg the percentage of BA.2 cases at 50.4% of all COVID cases in a six-state region of the Midwest that includes Illinois, Indiana, Michigan, Minnesota, Ohio and Wisconsin. In the United States as a whole, the CDC estimates that 54.9% of all COVID cases are tied to the “stealth omicron” variant.
The variant had already been detected in Illinois earlier this year.
Northwestern Medicine's Center for Pathogen Genomics and Microbial Evolution said the subvariant was found in a Chicago resident who was tested for COVID-19 on Jan. 18.
While cases nationwide have begun to rise in recent weeks, case numbers in the state of Illinois have remained largely stable. As of Tuesday, the state is averaging 1,178 new cases of COVID per day, an increase of 10% in the last week.
Hospitalizations remain near record lows, as do ICU admissions because of COVID, but officials say they will continue monitoring COVID trends in the event that a significant uptick in cases is observed.
Chicago Department of Public Health Commissioner Dr. Allison Arwady said while the COVID risk remains low in the city, data shows the number of cases of the BA.2 subvariant are doubling every week and the the city reports slight increases in daily COVID cases and positivity rates.
"I am pleased that one month after lifting the universal mask mandate and vaccine requirement for certain indoor public settings here in Chicago, the city remains in good control," Arwady said in a statement Wednesday. "It is not surprising to see a slight increase in cases as behavior changes, but we continue to monitor this closely. If the increase in cases does concern people, the most important thing you can do to protect yourself from severe outcomes remains the same: ensure you are up to date with your COVID-19 vaccinations.”
Small increases in overall case rates have also been noted in New York, and in hospital admissions in New England.
While numbers are still low in the city in terms of new COVID cases, the uptick in cases has been noted by health experts.
"At this point, we've not seeing major signs like we're seeing in Europe, but while we continue to watch, we'll have a better sense of this honestly, probably by the end of the month when BA.2 will be predominant here," Arwady said last week.
Why is the U.S. monitoring Europe?
The World Health Organization last week reported that the number of new coronavirus cases increased two weeks in a row globally, likely because COVID-19 prevention measures have been halted in numerous countries and because BA.2 spreads more easily.
There are signs in other countries currently experiencing an uptick in cases due in part to BA.2 that transmission may lead to a rise in hospitalizations and possibly even deaths.
"It is still now taking hold as the dominant variant in many countries ... Denmark, India, Philippines, UK, Switzerland, Sweden, Norway, Belgium, Hong Kong, South Africa and many more regions," said Huhn. "So particularly in the UK, where we now see that this is the dominant strain, we've seen some increased cases over the past several weeks, a doubling in the cases; we've seen increased hospitalizations and a little bit of signal for increased deaths. So with all these variants that have circulated throughout the past two years, many of the trends that start in Europe, and particularly in the UK, eventually, we see that here in the U.S. So that's why we're on heightened alert with the increase in cases of BA.2, increase in hospitalizations in the UK as an early warning signal for what could potentially occur here in the United States."
Numerous countries across Europe, North America and elsewhere recently lifted nearly all their COVID-19 protocols, relying on high levels of vaccination to prevent another infection spike even as the more infectious omicron subvariant is causing an uptick in new cases.
China locked down Shanghai this week to try to curb an omicron outbreak that has caused the country's biggest wave of disease since the virus was first detected in the Chinese city of Wuhan in 2019.
British authorities, however, have said that while they expect to see more cases, they have not seen an equivalent rise in hospitalizations and deaths.
Angarone said Europe is typically up to a month ahead of the U.S. in its COVID outbreaks.
"We often look at Europe as being that kind of bellwether of 2, 3, 4 weeks kind of ahead of us," he said. "So are we going to see this kind of increase in a month or so? And we just don't know."
Arwady said she's "concerned" about the situation in Europe and her team is in communication with officials there.
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.
According to Ghinai, evidence so far also suggests infection with one omicron sublineage is believed to provide protection from other omicron sublineages, but Huhn noted that reinfection is possible, though rare.
"I think it's very likely that what we've seen in Europe, where BA.2 is increasing in relative proportion, is going to happen here," Ghinai said. "We're going to see BA.2 causing an increase in proportion of the number of cases. We've already seen that."
Arwady stressed that while the rise of COVID in other countries could be a sign of what's to come, it's not a guarantee.
"It is not a for sure thing, to be clear, that we will follow. We may, but there are some other countries that have gone through an omicron surge and we've not seen that resurgence yet," she said. "So we're still watching."
