He was detained again in April 2015 for hanging a sign outside his home in protest of municipal elections, he added.
The United States appealed on Tuesday for Cuba to release jailed dissident Vladimir Morera Bacallao, citing his increasingly poor health after he launched a hunger strike in October to protest his imprisonment for expressing political dissent.
State Department spokesman Mark Toner told a news briefing that Washington is "deeply concerned" about Morera Bacallao's deteriorating physical condition and "urgently calls" on Havana to release him from prison.
Morera Bacallao was one of 53 prisoners of concern to the United States who were released shortly after the December 2014 announcement of President Barack Obama's new policy direction on Cuba, Toner said.
But he was detained again in April 2015 for hanging a sign outside his home in protest of municipal elections, he added.
"He's now in the hospital reportedly in very serious condition," Toner said.