Microbes and the dust they ride in on.
D000349:Africa; D000392:Air Movements; D001267:Atlantic Ocean; D001419:Bacteria; D004391:Dust; D005658:Fungi; D006801:Humans; D006967:Hypersensitivity / Q000209:etiology; D011634:Public Health; D012621:Seasons
D004391:Dust