Disclaimer: There are many diseases, and this list is my personal opinion based on several factors mostly deadliness & contagiousness.
There are no infectious diseases as of now that are highly infectious and also highly deadly.
Simple logic: if there was then we would all be immune to it and therefore low death rate, OR we would not exist we'd have been wiped out long ago :)
Diseases we see as trivial now were probably THE VERY WORSE that wiped out huge numbers are could have ended the human race and deserve respect, but the survivors were immune to it and the rest disappeared of the gene pool, so now they are not very deadly.
Important: I am not a medical doctor, not an expert in diseases, I even dropped biology as soon as I had the option in my first year of high school.