Brain Amoebas. Organ Transplants. Brrr. | Wired Science | Wired.com

Nightmare scenario: New disease arises. It's rare enough that there aren't many known patients, and so it isn't well-studied — and because it isn't well-studied, there aren't agreed-upon treatments or accurate tests for it, and there isn't a good understanding of situations where the infected might pose an unusual risk to others.

Situations, for instance, like organ transplants.

The CDC's weekly bulletin today describes that nightmare scenario come true. Last year, four people received the kidneys, heart and liver of a 4-year-old boy who died in Mississippi of encephalitis that was assumed to be a rare reaction to flu infection. Weeks after the transplant, the two kidney recipients developed neurological symptoms — spasms, seizures, visual disturbances — and were hauled back to hospitals for evaluation. MRIs showed ring-shaped lesions in both their brains. That sent investigators back to re-examine the boy's death — and revealed that while he did have encephalitis, it wasn't because of flu.

It was because he was infected with a newly recognized pathogen, Balamuthia mandrillaris, a species of amoeba. It had passed to the four recipients via his organs, and grew in them with an assist from the immune-suppressing drugs they were taking to prevent rejection.