Two patients have died after contracting a fungal infection linked to pigeon droppings at the Queen Elizabeth University Hospital in Glasgow.

The individuals are thought have caught the airborne disease at the hospital after inhaling the fungus cryptococcus, typically found in soil and pigeon droppings.

NHS Greater Glasgow and Clyde (NHSGGC) has launched an investigation into the outbreak. It said the likely source of the pigeon droppings was a non-public room, thought to contain machinery, which has now been cleaned.

NHSGGC said “control measures” had been introduced. Portable HEPA air filter units have been installed in specific areas as an additional precaution. In addition, a small number of vulnerable paediatric and adult patients are receiving medication to protect them against the airborne infection, which is a Cryptococcus species.

The health board said that the second patient who died was elderly and the death was due to an unrelated matter. It said it could not share further details of the case because of patient confidentiality.

A NHSGGC spokesman said: “Our thoughts are with the families at this distressing time.

“Due to patient confidentiality we cannot share further details of the two cases.

“The organism is harmless to the vast majority of people and rarely causes disease in humans.”

Teresa Inkster, NHSGGC lead consultant for infection control, said: “Cryptococcus lives in the environment throughout the world. It rarely causes infection in humans. People can become infected with it after breathing in the microscopic fungi, although most people who are exposed to it never get sick from it.”

She said there had been no further cases since control measures were put in place. “We are continuing to monitor the air quality and these results are being analysed. It remains our priority to ensure a safe environment for patients and staff,” she added.

Speaking to the BBC, Professor Hugh Pennington, of Aberdeen University, said he was surprised to learn of the infection.

The epidemiologist said: “It is very unusual in the UK.

“It is quite common in other parts of the world, particularly in tropical parts and in the US and in countries like that, where they have more problems with this particular kind of fungus.”

Prof Pennington said people with weak immune systems are most at risk.

He added: “When it gets into the blood stream a lot of people have fairly straightforward infections and it settles in the lungs but the big problem with this is that it can cause meningitis and, as we know, meningitis can be a very serious infection.”

Prof Pennington said anti-fungal drugs are used to treat the infection but warned it can be fatal if it is not diagnosed.

The expert said a key priority would have been stopping the airborne infection from entering the hospital’s ventilation system.

He added: “Obviously they have stopped the pigeons getting into the machine room.

“It surprises me slightly that there was any there in the first place.”