 Unique recombinant forms (URFs) are mosaic viruses that have not spread geographically.They are also reported in areas where multiple viral clades intersect.In 2004, a study by "AIDS" on sex workers in Nairobi, Kenya reported URF generation in a woman initially infected with clade A, and then 9 years later acquired clade C, which recombined with the initial infecting virus to form a recombinant of clades A and C that fully replaced the parental clade A virions.