Invasive fungal infections often cause multisystemic disease including non-specific signs such as anorexia, weight loss, lethargy, and fever unresponsive to antibiotics. For some of the fungal pathogens there are specific non-invasive tests. For many there are not. For the latter, a broad non-invasive biomarker such as Beta-D-Glucan (BDG), might help support the diagnosis. Many opportunistic molds, enzootic dimorphic fungi, Pneumocystis, and even the fungal-like organism Pythium contains BDG in the cell wall.