How pathogens can survive in aquatic environments

This article may give some insights into how P. ramorum can persist in a stream environment:

Islands of Germs: Researchers Discover Pathogens Floating on Tiny Clumps of Aquatic Detritus

Researchers have found evidence that "marine snow"--aggregates of organic material floating in water bodies--may act as microscopic, island-like refuges for pathogens, or disease-causing organisms. This detritus may skew water sampling procedures and mathematical models used to predict the transmission of waterborne diseases to humans.

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