What is aspergillus fumigatus? how does it make people sick?

Aspergilus: fumigatus is a fungus, present everywhere, indoors and outdoors, more in damp/humid areas, some people are allergic to its microscopic size spores, the allergic inflammation itself is what causes the problem either in the upper airways (nasal cavity and sinuses) or the lower airways (bronchi) , ranges from simple to severe inflammation with different symptoms, and isn't contagious