Pathogen fungi (organisms such as bacteria and viruses provoking pathologies), are eukaryotes, that is they belong to the same order of edible fungi and they can live in symbiosis with the animal or vegetal host. If the coexistence often turns out to be mutually beneficial, in some other cases the fungus can be extremely harmful for the host.

Aspergillus fungi, for example, are one of the most common strains, present in any environment and infecting both animals and vegetables as well.
Human beings are therefore constantly in contact with fungi, developing severe pathologies or allergic reactions (as for Aspergillus fumigatus and Aspergillus clavatus). Some strains, however, in the case of immune-deficient patients, can lead to invasive infections or severe pathologies. Another type of widespread fungi belong to the Candida group and they typically affect the women urogenital system. Such microorganisms often play a leading role in severe pathologies, mainly in immune-deficient patients or patients with consistent immune-deficiencies depending on other pathologies.

The spreading of fungi is through direct contact or through the air dispersion of their spores, the most dangerous infection mode as people can be affected by often severe respiratory pathologies, sometimes even leading to death. A correct disinfection can avoid any infection proliferation and spreading as well.