Any data on what happens on exposure to other mammals/vertebrates? Since it's killed(woodified?) all humans who came in contact (so far,) wondering if it has a reproductive cycle specifically geared to infect horses. If it does only affect humans, this might imply man-made origin, or at least, conscious design to work only on humans. Though it's notable that the oil in poison ivy and oak seems only to negatively affect humans. Birds & other mammals are usually fine. Did you have that in mind when you wrote this?
Ah- cellular structure! Is there any, or is it made of dead wood? Given, of course, it'd be hazardous to obtain and work with samples. Though truthfully, biopsy results might be better [REDACTED.] Don't want to take out the mystery…