After one of family members was diagnosed with Lyme disease, actor Chris Meloni had a lot of questions, but he knew one thing for sure: Life as he knew it had changed. "If Lyme disease is part of your life, your life will literally will never be the same," the “Law & Order: Organized Crime” star tells TODAY.com.

As an ambassador for the Global Lyme Alliance, the father of two has recently been focused on raising awareness of the tickborne illness, especially how difficult it can be to diagnose in some people. In the fall, he and attended an event for the organization, where he gave a speech. In an Instagram about the evening, he called Williams "a tenacious warrior" for efforts to help their family member get the care they needed.

In an interview with TODAY.com, Meloni opens up about his family member's journey with Lyme disease and his advocacy work. in his family member were a bit confusing at first, Meloni explains — and there were quite a few of them.

"We first thought we were dealing with the stomach flu," he recalls. Antibiotics seemed to remedy the issue at first, but symptoms soon returned, including brain fog, fatigue, joint pain, migraines and depression. "Before you know it, you’re dealing with a completely debilitated human being," he recalls of his loved one.

After a litany of tests and visits to specialists, from gastroenterologists to neurologists, a diagnosis finally came back. Beforehand, Meloni didn't know much about , a condition that the describes .