Dengue fever infections dropped dramatically in an Indonesian study where a type of bacteria was introduced into disease-carrying mosquitoes, offering hope in the battle against an illness that sickens millions annually around the world.Results of the three-year study, published in the New England Journal of Medicine this week, found that infecting dengue-carrying mosquitoes with a harmless bacteria called Wolbachia led to a 77 percent drop in human cases.Infections requiring hospitalisation