Mr Norris was the only person to die from an anthrax infection
A medical expert has told a fatal accident inquiry there was no "simple answer" why only one man had contracted anthrax from infected drums.
Christopher "Pascal" Norris, 50, died after attending classes where two drums used were later found to carry spores.
One theory was that Mr Norris, who was in remission for leukaemia, may have had a weakened immune system.
However, a consultant haematologist said that did not explain why he alone had contracted the infection.
Ashok Okhandier said many factors, including the common cold, could weaken the immune system.
Mr Norris, from Stobs near Hawick in the Borders, used a drum he made himself when attending two classes in Roxburghshire days before his death.
He is not thought to have used the infected drums at the class, although people sitting nearby were playing them.
Mr Norris, 50, died in the early hours of 8 July 2006, after being rushed semi-conscious to Borders General Hospital the day before.
Not suspecting anthrax, Mr Okhandier said he feared Mr Norris's leukaemia from 2002 had returned, but blood tests showed no sign of the cancer.
Brain and lung scans revealed Mr Norris had severe pneumonia and meningitis, caused by an unknown infection.
The root of the infection, anthrax, was not known until laboratory tests came back two days after his death.
At the inquiry at Edinburgh Sheriff Court, fiscal depute Martin Macari asked Mr Okhandier if the reason Mr Norris had picked up anthrax could be explained by his earlier leukaemia.
"One of the parts of this inquiry is to establish why Pascal Norris suffered from anthrax when so many other people who were exposed to this did not," said Mr Macari.
"Obviously one major health factor was that he had leukaemia and was in remission.
"Would that explain why he alone was affected?"
The consultant replied: "I don't think there's a simple answer to that."
The inquiry continues.
Anthrax is caused by the spore-forming bacterium Bacillus anthracis.
It most commonly occurs in animals such as cattle, sheep and goats, but can also occur in humans when they are exposed to infected animals.
Health experts have stressed it is not passed from person to person.