 When two or more viruses , each containing lethal genomic damage , infect the same host cell , the virus genomes can often pair with each other and undergo homologous recombinational repair to produce viable progeny . This process , known as multiplicity reactivation , has been studied in several bacteriophages , including phage T4 . Enzymes employed in recombinational repair in phage T4 are functionally homologous to enzymes employed in bacterial and eukaryotic recombinational repair . In particular , with regard to a gene necessary for the strand exchange reaction , a key step in homologous recombinational repair , there is functional homology from viruses to humans ( i. e. <unk> in phage T4 ; recA in E. coli and other bacteria , and <unk> and <unk> in yeast and other eukaryotes , including humans ) . Multiplicity reactivation has also been demonstrated in numerous pathogenic viruses . 
