COCOA, Fla. (CNN) – Spencer Rollyson says he experienced mild COVID-19 symptoms in May and didn’t think much of it.

“I had symptoms for a few days and it went away after a couple weeks, and I was fine after that,” said the 21-year-old Rollyson. “So I thought.”

He said initially, his symptoms felt like those of the flu or a cold. Then, just weeks later, he said, he nearly lost his life.

“About a week and a half, two weeks later, I started feeling bad,” Rollyson said.

He said he knew something was wrong when he went to work wearing a jacket to ward off the rain and ended up keeping it on after the rain had stopped despite working outside in Florida heat in the 90s. “I was still freezing,” he said.

Rollyson said he went to the emergency room with a 103.4-degree fever and underwent several tests, including blood work, chest X-rays and CT scans.

He said everything came back clear. “They had no idea what was going on,” he said.

Two days later, he was in the ICU.

“That’s when everything started shutting down,” he said. “In that two days, my body rapidly declined.”

He said doctors told him that as his body was trying to fight off the virus, it went into “a hyperactive mode” and eventually started “attacking” his own body. As a result, he suffered heart failure, acute respiratory failure and severe sepsis.

“I never thought, at 21, I would be on the verge of death,” he said. “I’m healthy and young, no prior health issues.”

Rollyson said after weeks of recovery, he’s still on medication that doctors have told him will likely continue for “the next year or two.”

Health experts have been stressing that while many young people go through the virus without symptoms, there’s still no way to know how they might react to COVID-19.

“All I have to say is just because you’re young doesn’t mean it’s not gonna affect you,” Rollyson said. “It’s not something to play around with. Just be safe, wear your masks, wash your hands. I can’t urge it enough.”

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