 The name was spelled according to the International Code of Zoological Nomenclature, since the organism was believed to be a protozoan.After it became clear that it was a fungus, the name was changed to "Pneumocystis jirovecii", according to the International Code of Nomenclature for algae, fungi, and plants (ICNafp), which requires such names be spelled with double i ("ii").Both spellings are commonly used, but according to the ICNafp, "P. jirovecii" is correct.