A report today (June 27) in PLOS Pathogens shows how inhaled fungal spores exit the lung and trigger a fatal infection in mice. The study solves a mystery of mycology: Why are spores of a certain fungal strain deadly while the yeast form of that same fungus is harmless? Study leader Christina Hull, professor of biomolecular chemistry and medical microbiology and immunology at the University of Wisconsin–Madison, focuses on Cryptococcus, the most deadly inhaled fungus. The short answer, she says, is that lung macrophages abandon their posts as bodyguards and begin smuggling spores into the bloodstream.