Letlow, 41, announced on Dec. 18 that he had tested positive for the novel coronavirus.
"Congressman-elect Luke Letlow, 41, passed away this evening at Ochsner-LSU Health Shreveport due to complications from COVID-19," his campaign manager, Andrew Bautsch, said.
"Letlow was admitted into a Monroe hospital on December 19 after testing positive for the coronavirus and was transferred to Ochsner-LSU Health on Tuesday, December 22 and placed in intensive care," he added.
Letlow, a Republican, won a runoff election on Dec. 5 for the 5th District seat, which represents Northeast and Central Louisiana, and was due to be sworn in on Sunday. He is survived by his wife and two children.
Louisiana Governor John Bel Edwards and U.S. House of Representatives Speaker Nancy Pelosi were among those that expressed sorrow and paid tribute to Letlow.