Three people died in Mammoth Lakes, California, from hantavirus pulmonary syndrome, the disease that suddenly killed actor Gene Hackman’s wife, Betsy Arakawa.

Hantaviruses are a family of pathogens spread by rodents, mostly mice, and excreted from their saliva, urine, and droppings. If left untreated, HPS can progress rapidly and result in low blood pressure, low oxygen levels, and death by organ failure.