As I said though, most historians go along with bubonic rather than either pneumonic or anthrax pandemics.
Still, the majority of historians support the theory that the bubonic plague caused the black death, so counterarguments have been developed.
The uncharacteristically rapid spread of the plague could be due to respiratory droplet transmission, and low levels of immunity in that period's European population. Historical examples of pandemics of other diseases in populations without previous exposure, such as smallpox and tuberculosis transmitted by aerosol amongst indigenous peoples of the Americas, show that the low levels of inherited adaptation to the disease cause the first epidemic to spread faster and to be far more virulent than later epidemics among the descendants of survivors. Also, the plague returned again and again and was regarded as the same disease through succeeding centuries into modern times when the Yersinia pestis bacterium was identified.