What Are Symptoms of ‘Stealth' Omicron or BA.2 as Subvariant Now Dominant Strain

With the BA.2 omicron subvariant now the dominant strain across Chicago and the U.S., what symptoms should you be watching for?

BA.2, also known as "stealth omicron," is considered a subvariant of omicron, but, according to Chicago's top doctor, the suvariant is now making up at least two-thirds of the city's COVID cases.

"By far, most of what we are seeing is BA.2," Chicago Department of Public Health Commissioner Dr. Allison Arwady said Thursday. "Not a surprise it is more contagious than B.1.1, but nothing leading to a major surge."

The city has seen its case metrics climbing in recent weeks.

As of Monday, the city was averaging 336 new COVID cases per day, up from 257 one week prior. The positivity rate is also up to 1.8%, an increase from the 1.5% reported last week. Hospitalizations and deaths have declined over the last week, though officials previously noted those metrics often lag behind a rise in cases.

Illinois has also seen a consistent rise.

"We are starting to see a steady increase in cases," Dr. Amaal Tokars, acting director for the Illinois Department of Public Health, said during a COVID briefing Tuesday. "Hospitalization in most places continues to be stable. We are seeing some just some bubbling up here and there and that's important to keep an eye on, but overall stable. Death continues to be stable. Again, here in Illinois, we are seeing these rising cases and a context of much lower cases than we had seen in the winter. But still notable and important to point out"

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.

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 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.

 Dr. Gregory Huhn, an infectious disease physician and the COVID-19 vaccine coordinator for Cook County Health, 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