can you catch alzheimers?

nature |  In the 25 years that John Collinge has studied neurology, he has seen hundreds of human brains. But the ones he was looking at under the microscope in January 2015 were like nothing he had seen before.

He and his team of pathologists were examining the autopsied brains of four people who had once received injections of growth hormone derived from human cadavers. It turned out that some of the preparations were contaminated with a misfolded protein — a prion — that causes a rare and deadly condition called Creutzfeldt–Jakob disease (CJD), and all four had died in their 40s or 50s as a result. But for Collinge, the reason that these brains looked extraordinary was not the damage wrought by prion disease; it was that they were scarred in another way. “It was very clear that something was there beyond what you'd expect,” he says. The brains were spotted with the whitish plaques typical of people with Alzheimer's disease. They looked, in other words, like young people with an old person's disease.

For Collinge, this led to a worrying conclusion: that the plaques might have been transmitted, alongside the prions, in the injections of growth hormone — the first evidence that Alzheimer's could be transmitted from one person to another. If true, that could have far-reaching implications: the possibility that 'seeds' of the amyloid-β protein involved in Alzheimer's could be transferred during other procedures in which fluid or tissues from one person are introduced into another, such as blood transfusions, organ transplants and other common medical procedures.

Collinge felt a duty to inform the public quickly. And that's what he did, publishing the study in Nature in September¹, to headlines around the world. “Can you CATCH Alzheimer's?” asked Britain's Daily Mail, about the “potentially explosive new study”. Collinge has been careful to temper the alarm. “Our study does not mean that Alzheimer's is actually contagious,” he stresses. Carers won't catch it on the job, nor family members, however close. “But it raises concern that some medical procedures could be inadvertently transferring amyloid-β seeds.”