Have you ever heard of serratia marcescens bacteria? Today they are a cause of hospital infections. In the 1960s, they were secretly sprayed across Washington, San Francisco, and New York.
Serratia marcescens is a bacteria that has earned a bad reputation for infecting people in hospitals. It may deserve an even worse reputation. It might have made people believe, for hundreds of years, that the blood of Christ was miraculously appearing in communion wafers.