Britain confirmed a case of Legionnaires' disease on Thursday and said the victim had worked at a laboratory at the centre of an outbreak of foot and mouth disease.
However, officials said there was no causal link and the man concerned had made a full recovery.
Legionnaires' is a form of pneumonia usually transmitted via water sources. The victim worked as a contractor at the laboratory site two months ago.
"There's no link between foot and mouth and Legionnaires', it just so happens that the man who contracted Legionnaires' had worked briefly at the Pirbright site," said a spokeswoman for the Health Protection Agency, which is investigating.
"It's just a coincidence."
As part of the investigation into how the man contracted the disease, the HPA is looking at all water sources where he may have been infected, including at the Pirbright laboratories.
"We look at all the different places this person has been," said a spokeswoman for the Health and Safety Executive, another government health department.
"Early findings show that there is nothing to suggest it (the institute) was not meeting the standards we expect it to meet."
The Pirbright site, near Guildford outside London, is where two research laboratories that handle various strains of the foot and mouth virus are located. The site is being investigated as a possible source of Britain's foot and mouth outbreak.
Legionnaires' disease is caught by inhaling small droplets of water suspended in the air that contain the Legionella bacterium.
