A study into people who died of a separate kind of brain disease after receiving injections of human growth hormone suggests that Alzheimer’s may also be a transmissible disease.

The findings have raised questions about the safety of some medical procedures, possibly including blood transfusions and invasive dental treatment, which may involve the transfer of contaminated tissues or surgical equipment.

The investigation has shown for the first time in humans that Alzheimer’s disease may be a transmissible infection which could be inadvertently passed between people.