Researchers at UC San Diego and Johns Hopkins used CRISPR-Cas9 to introduce a naturally occurring variant in the mosquito FREP1 gene that makes mosquitoes refractory to malaria infection. This single amino acid change prevents Plasmodium parasites from traversing the mosquito gut to salivary glands, halting transmission. The approach employs an allelic-drive system to spread the protective variant efficiently through mosquito populations without inserting foreign genes. This method offers a new strategy distinct from suppression or antibody-based modification of mosquito populations.