Female mosquito larvae (top) are separated from male ones (bottom) at a "sex separation area" inside Sun Yat-Sen University-Michigan State University Joint Center of Vector Control for Tropical Disease, the world’s largest "mosquito factory" which breeds millions of bacteria-infected mosquitoes, in the fight against the spread of viruses such as dengue and Zika, in Guangzhou, China July 28, 2016. REUTERS/Bobby Yip