This man ingested a tapeworm that had cancer. Then it gave him cancer.

When doctors began to examine the rapid-forming lung tumors that swiftly killed a 41-year old, HIV-positive Colombian man, they were shocked to discover that the cancerous cells were not, as one would expect, human.

“We were amazed when we found this new type of disease,”Atis Muehlenbachs, a CDC researcher who treated the unidentified man explained. “Tapeworms growing inside a person, essentially getting cancer, that spreads to the person, causing tumors.” The details of the whole ordeal are described in this month’s New England Journal of Medicine.

The man had previously been hospitalized for respiratory issues and drastic, uncontrollable weight loss. When he was admitted most recently and the cancer was discovered in his lungs, doctors weren’t immediately sure what to make of the tumors. Seventy-two hours after the tapeworm had been discovered and the DNA within the tumors had been matched to the tapeworm’s, the man was dead.

The team of researchers who studied the man explained that his is a highly unusual case. Never forget: nature is terrifying.