A romantic adventurer's marriage proposal to his girlfriend on Peru's Inca Trail went perfectly but their plans for a future life together were thrown into jeopardy after he was attacked by a flesh-eating virus.

Adam Spencer, 23, from Veneta, Oregon, was elated when long-term girlfriend Shalynn Pack agreed to marry him while they were on a six-month journey across South America.

Two months into their journey, however, a spot developed on his face after he was bitten by a sand fly while crossing the Bolivian salt flats in the Amazon.

The spot grew and hardened into a scab, before it began weeping pus. He was treated with antibiotics but the spot was still there when he returned to the US.

His GP, Dr Stephan Ames, said: "Adam came in with a wound on the right side of his face. It was firm, but soft and mushy on the inside.

"I was concerned it was a staph infection, which can infect multiple organs and could cause him to die."

He gave his patient penicillin for a week and tests showed no sign of a staph infection but the condition continued to spread, growing closer to his eyes.

The couple became even more concerned when Spencer developed a blockage in his throat and was unable to swallow.

"It was terrifying to think, I'm just watching him die," said his fiancee.

Specialists were called in and diagnosed his condition as an infection by a flesh-eating parasite. Three weeks of treatment eventually cleared it but he was left with a two-inch scar on his cheek.

"Scar or no scar he's still the most handsome man I know," Pack said.

The story will feature on the show Monsters Inside Me on the Discovery Channel.