Merkel cell polyomavirus (MCV or MCPyV) was first described in January 2008 in Pittsburgh, Pennsylvania. It was the first example of a human viral pathogen discovered using unbiased metagenomic next-generation sequencing with a technique called digital transcriptomic subtraction. MCV is one of seven currently known human oncoviruses. It is suspected to cause the majority of cases of Merkel cell carcinoma, a rare but aggressive form of skin cancer.