Let's not jump to conclusions. That guardian article is about a pre-print study that used frozen brain samples from a single tissue bank, and RNA sequencing was done on a single machine.
There's a lot of controversy around this[1], because contamination is possible and it's known that the blood brain barrier weakens with age. The sample are all from older individuals.
Contamination is possible, but it's hard to explain the results that way. Definitely needs replication, of course.
I don't see the point of the samples all being from older individuals. Even if it exclusively occurs in older individuals (unlikely), it would still mean that the blood-brain barrier is not 100% effective (which we already know to be true).
There's a lot of controversy around this[1], because contamination is possible and it's known that the blood brain barrier weakens with age. The sample are all from older individuals.
[1] https://www.news-medical.net/health/Is-there-a-brain-microbi...