. >> reporter: university of florida professor phil lounibos has studied mosquitoes and the diseases they carry for over 40 years. he's not involved with the proposed g.m. experiment in the keys. >> we believe, those of us who have worked with mosquitoes, that the probability of something going wrong is not very high. >> reporter: lounibos is convinced the trial would be safe, but he questions its effectiveness. he says other mosquito species can carry dengue, and the local bugs could evolve to outsmart the genetically modified males. >> in the absence of dengue, the absence of a really significant threat of dengue, i see the oxitec implementation in the keys in the context of strong public opposition to be inappropriate. >> reporter: globally, dengue has surged 30-fold in the past 50 years, and increased travel from endemic areas along with warmer temperatures means the threat is spreading. i asked de mier what might happen if she blocks the trial and there's another, more serious dengue outbreak in the keys. do you worry that someone would call you up and say "mila you stood in the