As omicron COVID cases continue to surge, with many states across the country reporting record case levels, when could the variant reach its peak?
Chicago's top doctor offered her predictions based on data from around the globe Tuesday, but said, in short, "we don't know when omicron is going to peak." There are some signs experts are watching for, however.
"I've been talking to the modelers and the epidemiologists," Chicago Department of Public Health Commissioner Dr. Allison Arwady said in a press conference Tuesday. "So in South Africa, which was the first place to really detect and see this huge surge of omicron, it took about four weeks for omicron to peak and then another couple of weeks for it to really come back down."
But, she noted, South Africa differs from many countries now experiencing the surge "in a number of ways, including high rates of infection, differing rates of vaccination, a much younger population with a median age under 30."
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"Just a different population overall," Arwady said. "So in a best case scenario, we would be looking probably at a peak in the first half of January, let's say."
Arwady said as of Tuesday she is 85-90% confident Chicago will see omicron cases peak in January, but only 50% confident that the peak will come during the first half of the month.
She said the best indicator of what could happen here comes from watching trajectories in Europe, the UK and even in New York City.
"We are watching really closely what is happening in Europe and in the UK, because sort of after seeing that surge in Southern Africa, the next place we really saw omicron surge was in the UK, in Europe. We have not clearly seen yet a sign of decrease in those settings. It's always a little bit tricky around the holidays because testing just gets disrupted in different ways. We have definitely seen signs of slowed increase, which we have also seen here in Chicago, but I will feel more reassured when I start to see some of those numbers come back down."
Arwady said if numbers begin to drop in Europe over the next two weeks, or in New York, she would expect Chicago to follow "a week or so later."
"We'll know much more in a week or so, I think particularly looking to Europe, but in the meantime, you know now is this time to get vaccinated really truly and especially for protecting the hospitals," she said.
Her predictions follow similar ones from Dr. Anthony Fauci, the top medical adviser for the White House, who on Wednesday predicted that the latest wave could hit its peak in the U.S. by the end of January.
"I would imagine, given the size of our country and the diversity of vaccination versus not vaccination, that it likely will be more than a couple of weeks, probably by the end of January, I would think," Fauci said on CNBC's "Closing Bell."
Chicago Mayor Lori Lightfoot also said this week she expects the omicron variant to peak “certainly by mid-January, if not a little later."
Currently, Chicago is reporting its highest case rate of the entire pandemic, with an average of 4,591 cases per day.
While she noted that the increase is in part due to an increase in testing over the holidays, many of which were done at home or for children in schools, the city's positivity rate sits at 23.6%, "the highest it's been since the first wave of the pandemic."
Intensive care unit hospitalizations are also up, nearing levels reported in December 2020, but remaining below the height of the pandemic.
As of Tuesday, the city was averaging 110 COVID hospitalizations per day.
"If we look at hospitalizations, this of course is what gives me pause, is what I'm watching the most closely," Arwady said. "The fact that we are seeing these high hospitalization numbers is the thing that gives me the most pause."
Arwady added that more than 90% of people hospitalized or in the ICU with COVID are unvaccinated.
It's a trend seen across the state, which on Monday set a pandemic record for hospitalizations.
Gov. J.B. Pritzker has already asked hospitals to pause elective and non-emergency procedures in anticipation of more COVID-19 patients and beefed up staffing at vaccination centers.
Also starting Monday, the city of Chicago and surrounding Cook County began requiring proof of COVID-19 vaccines at indoor venues including restaurants, gyms and museums.