Wolbachia is a naturally occurring bacteria with virus-blocking abilities. It stops viruses such as dengue from growing inside the mosquitoes and being passed to humans. The bacteria is harmless to animals, people and the environment. Dengue is transmitted to humans through the bites of infected female mosquitoes from the Aedes aegypti species. In Saudi Arabia, scientists microinjected Wolbachia into Aedes aegypti eggs then released the adult mosquitoes to breed and spread. Since 2021, they’ve released 5 million mosquitoes. In one Jeddah district, the prevalence of mosquitoes resistant to dengue has reached 80%.