miasma and contagion co-existed in the past -- they were not mutually exclusive. (are they mutually exclusive nowadays?)

"The questions were: Was it anthrax? If so, was it a genetically engineered bioterrorism strain, or a strain that normally lives in the soil? How dangerous was it? And the answers, Dr. Musser realized, could come very quickly from newly available technology that would allow investigators to determine the entire genome sequence of the suspect micro-organism. " Yet the patient in question had died, his lungs weakened from the welding work he did.