Music fans across the globe continue to mourn the death of Prince, who died suddenly on Thursday morning at his estate in Paisley Park, Minnesota.

Details on what caused the singer’s death are scarce.

In a phone interview with MSNBC anchor Brian Williams, Aretha Franklin hailed Prince as one of music’s most unique artists. The Queen of Soul also wondered aloud if his death was related to the Zika virus.

“They’re saying flu-like symptoms,” Franklin said. “I’m wondering if it had anything to do with this Zika virus.”

Williams wisely didn’t continue the speculation, shifting instead to a question about how to handle all of Prince’s unreleased music.

Earlier in the interview, Franklin heaped praise on Prince as a musical genius.

“It’s such a blow,” Franklin said of the singer’s death. “It’s really surreal. It’s just kind of unbelievable […]. He was such an original. He was definitely an original and a one of a kind. There truly was only one Prince.”