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The blight — caused by the bacterium erwinia amylovora — is native to the United States and predates the introduction of apple trees to North America.

Pirhonen, M., Flego, D., Heikinheimo, R. & Palva, E. T. A small diffusible signal molecule is responsible for the global control of virulence and exoenzyme production in the plant pathogen Erwinia carotovora.

According to the CDC’s 2003 Guidelines for Infection Control in Healthcare Facilities, clinicians in a 1974 case suspected that a plant pathogen called Erwinia, identified in a newborn who died from septicemia, had come from plants in the delivery room, but no direct link was established.