The first confirmed omicron variant case in suburban Cook County has been reported, but what do we know about the person's symptoms and how they were exposed?
Here's a look at what officials said we know so far about the case:
Where was the case reported?
The Cook County Department of Public Health announced the variant was identified in a case Tuesday, but did not specify which suburb the variant was found in. When asked, officials cited privacy concerns for why they could not say which suburb the case was reported in.
"It's not like we're saying there are 20 new cases in this municipality or 30 in another," Dr. Rachel Rubin, co-lead and senior medical officer for the Cook County Department of Public Health, said. "So, this is the only one."
Was the person vaccinated?
The case, the first known case of omicron in suburban Cook County, was reported in a person who had received at least two doses of the coronavirus vaccine, officials said.
Rubin noted the person had received their last dose of the vaccine "several months" ago but could not give a specific date.
"We know that they've had at least two doses of the vaccine. And we don't know yet the status of a booster in this individual, but we're investigating," she said.
How was the person exposed?
According to Rubin, the person had contact with someone else who tested positive for the omicron variant, which led them to get tested despite being asymptomatic.
"It was through a contact with somebody else that had it," Rubin said.
Rubin could not say whether that contact was in the state of Illinois or out of state or the country, however.
Are more cases expected?
Additional cases could soon be identified as "there are other cases that are currently being genotyped for omicron," the Cook County Department of Public Health stated.
"We're investigating positive cases that are also contacts of this case, as well as a couple of other individuals that do not seem to have a direct contact, but these investigations are underway right now," Rubin said.
What do health officials expect next and what is being done to prevent spread?
County officials say delta case counts have significantly increased in the days and weeks before the arrival of omicron, but said they anticipate rapid spread of the new variant.
“As expected, omicron has arrived in suburban Cook County and we must take every possible precaution to prevent this highly-contagious variant from spreading rapidly,” Dr. Rachel Rubin, co-lead and senior medical officer for the Cook County Department of Public Health, said in a statement. "Vaccinations, including booster shots, are vital. Masking indoors in all public spaces is mandated in the county and must continue. And we urge unvaccinated residents to not attend any holiday celebrations or social events during this time.”
What about other cases in Illinois?
So far only one other case has been confirmed in Illinois, according to the state's health department.
The case was reported in a fully vaccinated city resident who had also received a booster dose but was visited by an out-of-state traveler who also tested positive for the variant. The resident did not require hospitalization, is improving and has been self-isolating since their symptoms began, officials said.
“While unsurprising, this news should remind Chicagoans of the ongoing threat from COVID-19, especially as families prepare to come together over the holidays,” Chicago Department of Public Health Commissioner Dr. Allison Arwady said in a statement. “We know how to slow the spread of this virus: get vaccinated, get boosted, get tested if you have symptoms or have been in contact with someone with COVID-19, and stay away from others if you test positive. Wear a mask indoors, avoid poorly ventilated spaces, practice social distancing, and wash your hands.”
Arwady added at the time that test results were pending for city residents who are known contacts of out-of-state or out-of-country omicron variant cases.
"We are following multiple individuals who we know had exposures, whether they were traveling in the U.S. or even internationally, and we have a pretty robust way to share information in a way to protect privacy, but allow us to do case investigation or contact tracing, including over state boundaries," she said.
So far the variant has already been detected in nearly two dozen U.S. states, with cases also reported in Minnesota and Wisconsin.