Kahlefeldt complained of pains in the left side of his chest after completing the world series race at Mission Beach on Sunday and underwent immediate chest scans.
“The x-rays showed there was a shadow on the left side of his lung and he is undergoing a CAT Scan and other tests to determine the diagnosis,” Triathlon Australia’s high performance manager Michael Flynn said.
“The Triathlon Australia team doctor spoke to Brad and the doctor at the hospital in San Diego and he will hopefully have some answers within the next 24 hours. He has told us that there is a possibility that Brad could have tuberculosis or even pneumonia – the next day or so will confirm that.
“For the moment we have to assume that it is tuberculosis and Brad has to remain in isolation until they determine the diagnosis one way or the other.”
Kahlefeldt and his former girlfriend, dual world champion Emma Moffatt, took an extended holiday in Vietnam and Cambodia at the end of the last international season and there is concern that he may have contracted the disease then.
Moffatt is showing no symptoms and finished a solid ninth in San Diego, but will also be thoroughly checked out if Kahlefeldt is diagnosed with tuberculosis.
The 31-year Beijing Olympian was having some chest symptoms and coughing up blood even before he raced in San Diego, but chose to ignore them so he could compete.
He was in the top ten at the end of the 40km cycle leg but faded to 24th in the 10km run to the finish line as he felt the pain in his chest.
Kahlefeldt was due to fly out for a training camp in Spain before for the next round of the world series in Madrid on May 26 and 27 but Triathlon Australia will not allow him to travel or train until he is receives a medical clearance.
Any serious medical condition would undermine his preparation for the London Olympics, given the proximity of the Games.