By Chris Tye

This story has been updated to more accurately reflect the Delta variant’s rise in Illinois

CHICAGO (CBS) — As COVID-19 cases are rising again in Illinois, while the more contagious Delta variant might not yet be the most common strain of the virus, it’s spreading quickly, and officials believe it’s responsible for the latest uptick.

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“We are sounding the alarm today because we are starting to see this uptick,” Mayor Lori Lightfoot said at City Hall Tuesday.An increase that we believe is because of the highly contagious Delta variant of COVID-19.”

But the sound of music will still race through Grant Park next week, and so will an expected 100,000 Lollapalooza attendees. Lightfoot said she does not have second thoughts about green-lighting it despite an uptick in COVID cases.

As of Monday, Illinois had a total of 10,592 COVID-19 variant cases. That is twice as many as it had on May 11.

“I’m a little concerned about what the future could hold,” said Dr. Allison Arwady, commissioner of the Chicago Department of Public Health.

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CBS 2 dug deeper into these numbers to see what the future might hold and discovered that among the six variants tracked by the Illinois Department of Public Health, the Delta variant, which gets the most attention, accounts for just 403 of those cases. The lesser talked about Gamma variant has four times more cases in Illinois — more than 2600 so far.

But those inroads are on a concerning trend line. As of Wednesday, cases of the Delta variant have nearly tripled over the last two weeks, whereas Gamma has risen just a little over 1% over that same period.

Dr. Stefan Green, director of the Genomics and Microbiome Facility at Rush University Medical Center, runs the lab at Rush that the City of Chicago commissioned last winter to track variants.

Green said, whether someone contracts the Gamma or Delta variant, the risk of hospitalization and death are similar, and getting vaccinated is a strong shield of protection against both.

“I think what everybody in my community is worried about is that if we don’t get vaccinated we will eventually get a variant that our vaccines are not effective against,” he said.

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The city also passed along a warning from the FBI Tuesday to people making fake vaccination cards to get into Lollapalooza or other events, saying that is both endangering the person with the fake card and breaking the law.