What a vast topic! You'll probably have to read lots in order to choose a specific topic that can be adequately written about.
and here: http://www.google.com/#hl=en&source=hp&q=health+public+worldwide&aq=f&aqi=g9g-m1&aql=&oq=&gs_rfai=Cjzs4L6V0TOuaEZXcygSRiYEGAAAAqgQFT9AmbmU&pbx=1&fp=93c3c78db929eee0
(Start with the sixth linked article.)
I think the most recent world event is the oil spills. Global warming is another topic. Another big issue is pesticide use and antibiotic use in healthy animals.