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.
It is found in respiratory secretions suggesting that it may be transmitted by a respiratory route. But it also can be found shedding from healthy skin, and in gastrointestinal tract tissues and elsewhere, and so its precise mode of transmission remains unknown.
Merkel cell carcinoma is mainly seen in older individuals. It is known to occur at increased frequency in people with immunodeficiency, including transplant recipients and people with AIDS.