As Davangere Dev–anand, a neurologist at Columbia University Medical Center, combed through the reams of scientific data on Alzheimer’s, he stumbled across a surprising idea – could an infection be involved in driving the disease?

“I was looking for an Alzheimer’s treatment approach that had a reasonable shot of working,” he says. “I found this old theory, going back 35 years, which linked herpes viruses to the disease, and there were all these indirect lines of evidence.”

The further Devanand looked, the more he found. Since the mid-80s, a handful of scientists around the world had doggedly pursued the idea that either a virus or a bacterium could play a role in Alzheimer’s, despite almost complete antipathy from those studying more accepted theories about the disease. Colleagues snubbed