As early as 1984, scientists reported seeing herpesvirus-like structures in KS tumors examined under electron microscopy. Scientists had been searching for the agent causing KS, and over 20 agents were proposed as the possible cause, including cytomegalovirus and HIV itself. The pathogen was ultimately identified in 1994 by Yuan Chang and Patrick S. Moore, a wife and husband team at Columbia University, through the isolation of DNA fragments from a herpesvirus found in a KS tumor in an AIDS patient. Chang and Moore used representational difference analysis, or RDA, to find KSHV by comparing KS tumor tissue from an AIDS patient to his own unaffected tissue. The idea behind this experiment was that if a virus causes KS, the genomic DNA in the two samples should be precisely identical except for DNA belonging to the virus. In their initial RDA experiment, they isolated two small DNA fragments that represented less than 1% of the actual viral genome. These fragments were similar (but still distinct from) the known herpevirus sequences, indicating the presence of a new virus. Starting from these fragments, this research team was then able to sequence the entire genome of the virus less than two years later.