Emerging and waning health threats. Polio and HIV are two of the most devastating diseases of our time – but they’re waning or, in the case of polio, on the verge of eradication. At the same time, Zika virus, Ebola flare-ups and other unexpected threats will make headlines in 2016, and pose challenges to global health security. For many health systems around the world, these dangers are already in the back yard.