Why does it take joint efforts to eliminate some diseases like malaria?

Although global efforts in the past decade have halved the number of deaths due to malaria, there are still an estimated 219 million cases of malaria a year, causing more than half a million deaths. In this forum article, we asked experts working in malaria research and control to discuss the ways in which malaria might eventually be eradicated. Their collective views highlight the challenges and opportunities, and explain how multi-factorial and integrated processes could eventually make malaria eradication a reality.

Keywords: Malaria, Plasmodium falciparum, Plasmodium vivax, Eradication, Epidemiology, Rapid diagnostics, Drug resistance, Mass drug administration, Vaccines, Vector control, Capacity building

i believe the answer is a