Merkel Cell Polyomavirus

Merkel cell polyomavirus (MCV or MCPyV), first discovered in January 2008, is one of seven human tumor viruses. It is suspected to cause most of Merkel cell carcinoma which is a rare, aggressive form of skin cancer. Around 80% of Merkel cell carcinoma tumors are found to be infected with MCV. It is found in respiratory secretions suggesting that it may be transmitted by a respiratory route. Usually the tumors with MCV viruses go through at least two mutations that render the virus non-transmissible.

Polyomaviruses are small, non-enveloped, double-stranded DNA viruses. MCV was the fifth polyomavirus that infects humans to be discovered. It is most closely related to African green monkey lymphotropic polyomavirus which is similar to MCV co-evolving with human primates.
Merkel Cell carcinoma is a highly aggressive skin cancer first described by Cyril Toker in 1972. The cancer cell type is a neuroectodermal tumor. It is rare compared to other skin cancers; however, incidences have tripled in the USA between 1986 and 2001. Generally, it is seen in older individuals. People who have Merkel cell carcinoma with this virus are not infectious to others because the virus in the tumor has mutated already and most people are naturally exposed to this virus as children. Prevention is similar to skin cancers such as avoiding sun burns and excess exposure to the sun. People with immunosuppression are at higher risk for this cancer.

Detection is still in the research phase and is not available as a clinical test. PCR is used to detect viral DNA. It is easy to get a false-positive through this process.

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