While many people are resuming normal activities after nearly 16 months of pandemic-induced restrictions, scientific experts say the danger from COVID-19 is far from over. The highly contagious Delta variant strain of the virus is spreading across the U.S. at a worrisome pace that has the CDC labeling it a “variant of concern.”

During an appearance on CNN, the former White House adviser on COVID, Andy Slavitt, described it in more colloquial terms, but with no less an emphasis on its potential danger.

“This is like COVID on steroids.”

He pointed out that people who are fully vaccinated have little to worry about from the variant. Those who have not gotten the vaccine however, are at much greater risk of becoming infected, according to Slavitt.

“If you haven’t been vaccinated, or you live in a community where there’s a lot of people who haven’t been vaccinated, this is a more virulent strain.” 

The Delta strain is thought to be 60% more transmissible than a previous variant, the Alpha. Delta was first noticed in India, where it spread rapidly last month to the point that the country’s hospitals were overwhelmed with COVID patients. The same variant made its way to the UK, where it has led to a spike in cases that has pre-empted Britain’s reopening plan. The World Health Organization says the Delta strain has been detected in 80 countries around the world.

“Globally, Delta is the most serious development that we know of in terms of the evolution of the virus,” said William Hanage, a Harvard epidemiologist told USA Today.