The World Mosquito Project cultivates and releases mosquitoes infected with a bacterium called Wolbachia which is passed down to future generations. The bacterium appears to block mosquitos from transmitting arboviruses (dengue, chikungunya & yellow fever) & Zika. – WTF Fun Facts
Source: Infecting Mosquitoes With A Bacteria Could Help In The Battle Against Dengue : Goats and Soda : NPR