For most people, the coronavirus is no laughing matter. But the Korean star known as Jaejoong of the K-pop group JYJ decided to pretend to have the virus on Wednesday in a misfired attempt at an April Fools’ Day joke.

He made the claim on his Instagram account, which had nearly two million followers, and his legions of fans reacted with shock and concern.

Social media lit up with expressions of support. News outlets and K-pop fan sites immediately covered the announcement. Jaejoong would have been among the biggest celebrities to become infected. South Korea was an early hot spot for the virus and had 9,887 confirmed cases as of Wednesday, including 165 deaths.