Fungal infections do not commonly occur in people with normal immune function. Systemic infections are the most serious and the most difficult to treat of the fungal infections. Some fungi only exist as yeast. Thermally dimorphic fungi are molds at room temperature and are yeast at body temp. It means the fungal microbe can adjust to body conditions and thrive there.
Fungal pneumonias are very serious.
More so than bacterial or viral. Of the modes of action we discussed it is only the cell membrane acting antimicrobial drugs that will be effective on most fungal infections. Usually we inhale the fungal spores . The spores lodge in the respiratory tract and germinate into the yeast phase which loves body temperature and thrives there. Usually fungal pneumonias are misdiagnosed as bacterial or viral and the wrong therapy is started.