UFC's return to South Florida is in need of a new main event.
Kawa said Romero became ill on March 21, with a high fever and pain throughout his body, and that the illness persisted until Sunday, when Romero told him he couldn't open his eyes.
Romero went to hospital on Monday and was diagnosed with a mild case of pneumonia, leading Kawa to pull his fighter from the bout.
Brazilian media outlet AgFight first reported the news.
It's unclear whether Souza will remain on the card, sources said, but UFC is actively seeking a new main event for the card. The promotion has approached other fighters about putting together a headliner that doesn't include Souza because marquee options are limited for the Brazilian.