An electrician working on a lengthy project at a farm caught a disease caused by a fungus that spreads from bird feces particularly if the feces are mixed with soil over an extended period. Following Sarti v. Salt Creek, Ltd. (2008) 167 Cal.App.4th 1187 and distinguishing Miranda v. Bomel Construction Co., Inc. (2010) 187 Cal.App.4th 1326, this decision holds that the trial court erred in granting defendant summary judgment. Here, as in Sarti, circumstantial evidence allowed a reasonable inference that defendant’s negligent actions were a substantial factor in transmitting the disease. The farm was infested for many years with flocks of swallows that roosted in a barn. Defendant swept the accumulating bird feces onto the dirt surrounding the barn, creating perfect conditions for growth of the fungus. While he worked on the farm, the electrician was housed in an RV parked near the barn the birds infested. Since it was reasonable to infer that the fungus originated in the soil around the barn, the trial court erred in excluding the testimony of plaintiff’s experts as speculative.