The yellow fever virus is the infection from a patient with yellow fever. Filterable virus comes from Martinus Beijerinck. After a while the term filterable was dropped and they just used virus.  They are clearly talking about poison. Thomas M. Rivers just said this infection was alive and the cause of disease. This was the greatest medical scam of all time. They used infected mouse brain and mixed it with the blood of a monkey and spun that mess up in a centrifuge machine and called the pellets the virus.