The men, both of Rochester, were cultivating cannabis for personal use when their health started to deteriorate, according a case published in the journal, Open Forum Infectious Diseases.

One of them, a 59-year-old man with a history of emphysema as well heavy tobacco and marijuana use, was hospitalized after suffering serious weight loss over the course of about six weeks. He also had a sore throat when he was admitted to Strong Memorial Hospital which had been making it increasingly difficult to swallow.

Doctors initially suspected carcinoma after scans showed a mass on his larynx — but a biopsy sample ultimately tested positive for a histoplasmosis infection.

The other man, who was 64 years old, was meanwhile hospitalized for hypo-osmolar hyponatremia — a condition in which sodium levels in the blood are abnormally low — difficulty eating, and severe weight loss. He also had a long history of tobacco and marijuana use and previously underwent a bypass surgery to better facilitate blood flow to his legs.

Doctors eventually determined he too was suffering from a histoplasmosis infection, a type of pneumonia caused by breathing in spores of histoplasmosis capsulatum.

He told doctors there was “a heavy bat infestation of his attic,” which, as a result, was covered in bat feces, or guano. He said he decided to use the waste to fertilize his marijuana, and then relayed his plan to the 59-year-old, who purchased his own guano online.

It is likely that during the fertilization process, the men breathed in harmful fungus spores released by the guano, leaving them both with pneumonia.