 Homologous recombination occurs in several groups of viruses . In DNA viruses such as herpesvirus , recombination occurs through a break @-@ and @-@ rejoin mechanism like in bacteria and eukaryotes . There is also evidence for recombination in some RNA viruses , specifically positive @-@ sense ssRNA viruses like retroviruses , picornaviruses , and coronaviruses . There is controversy over whether homologous recombination occurs in negative @-@ sense ssRNA viruses like influenza . 
