Yes, but we can treat/cure Malaria, HIV, and TB. We have establish methods to prevent their spread (sans DDT and political correctness with HIV). We have no prevention methods, treatments or cures for Ebola. And the CDC/administration is refusing to use the best known tools to prevent its spread.
There are DDT and pyrethroids (stuff bed nets are currently treated with) resistant mosquito populations now. So DDT is no longer the saving grace that the chemical happy crowd is always pointing at.
http://www.sciencedaily.com/releases/2014/02/140224204808.htmHIV/AIDS, last time I checked there was no cure, what is interesting it spreads in similar ways of the different Ebola species, not all but many of the way. Currently HIV is a manageable disease but it will kill you eventually, quicker unless you got Magic Johnson's money. Plus if I remember correctly HIV/AIDS had spread to a lot of people before they really knew what it was and how it spread. Not sure how the non politically correct method would have worked, also where would have put all those people infected with HIV? FDR's abandoned internment camps?
Yes, Malaria can be treated, but it is also not contagious, have to be bit by the mosquito that has the malaria parasite.
Maybe things like Marburg and Ebola viruses are nature's way of controlling the population of a certain species? This time its the human species turn for a population reduction? There are a lot more viruses and bacterial species then there is of any vertebrate or invertebrate and they evolve a lot faster than the other animals, I think Darwin would have appreciated the wee nasty beasties.