The highly transmissible Delta (B.1.617.2) variant of COVID-19 is spreading so rapidly in the United States that it is expected to become the dominant variant within weeks.

At least 84 COVID-19 cases in Illinois have been linked to the Delta variant as of mid-June, according to Illinois health officials.

“We are very concerned about this variant because it is more contagious and may cause more severe disease,” Jennifer Grant, MD, NorthShore Infectious Diseases physician, said. “While life seems like it’s going back to normal, this variant reminds us all that COVID-19 is still present in our communities and a real threat for the unvaccinated.”

Here, Dr. Grant highlights four things you need to know about the Delta variant.

It’s more contagious and may be more dangerous than other variants.

Delta is believed to be the “fittest” COVID-19 variant yet – meaning it spreads very efficiently and may cause more severe disease. The World Health Organization labeled it as a “variant of concern” in early May.

Delta currently appears to be around 60 percent more transmissible than the Alpha (B.1.1.7) variant, which was the dominant strain in the United States this past spring.

Additionally, early data from the United Kingdom demonstrated that people infected with Delta are around twice as likely to be hospitalized, compared to those infected with the Alpha variant.

Infections caused by the Delta variant are increasing.
Experts report that the Delta variant currently makes up about 20 percent of COVID-19 cases. Two weeks ago, it only represented 10 percent of cases. The rapid increase in cases is leading experts to fear it could lead to another wave of cases this fall.

It may affect young people more often.
Because the Delta variant is more contagious, it is also likely to affect children more so than prior strains, however severe disease in children is still rare. This is concerning because young children are not currently eligible for vaccination, but Dr. Grant expects data and Food and Drug Administration review of COVID-19 vaccines in younger children this fall.

Vaccination is the best way to limit the spread of the Delta variant.
Fully vaccinated individuals are highly protected against the Delta variant. Data currently suggest that the Delta variant is spreading faster in regions of the United States with lower vaccination rates.“Vaccination is our best defense against pockets of outbreaks around the country,” Dr. Grant said.