The outbreak of invasive fungal infections among patients who received injections of contaminated methylprednisolone acetate prepared by the New England Compounding Center (in Framingham, Massachusetts) is a disturbing tragedy, already the largest health care–associated fungal outbreak reported in the United States, with 693 cases and 45 deaths reported as of January 28, 2013.1 Effectively responding to this catastrophic event required rapid actions by clinical and public health practitioners who worked to ensure discontinued use of the suspect medication, notify at-risk patients and their physicians, and decipher the many unknowns about the outbreak to provide the best guidance for minimizing harm.