WASHINGTON (AFP) - US researchers have discovered a new virus they believe may be linked to a rare but extremely lethal type of skin cancer, a study released Thursday said.

Merkel cell carcinoma mostly afflicts the elderly and people with weaker immune systems, including AIDS and transplant patients.

In a study published in the journal Science, a research team from the University of Pittsburgh Cancer Institute said it found a strong link between the rare cancer and a new virus they called Merkel cell polyomavirus (MCV).

"This is the first polyomavirus to be strongly associated with a particular type of human tumor," said Patrick Moore, a member of the research team.

While the researchers emphasized that more study was needed to confirm the link, they said the discovery could lead to new cancer treatments.

The scientists identified the virus's DNA sequence in 80 percent of Merkel cell tumors. The virus penetrates tumor cells in a pattern indicating that the infection precedes the cells' growth into a cancer, they said.

Merkel cancer cases have tripled over the past 20 years to about 1,500 a year, and about half the patients with advanced stages of the cancer live only nine months. Two-thirds die within five years.

The researchers believe the new virus produces a carcinogenic protein and blocks a gene that stops the growth of cancer cells.

"Information that we gain could possibly lead to a blood test or vaccine that improves disease management and aids in prevention," Moore said.

The researchers noted that a vaccine now exists to prevent cervical cancer, which is caused by another virus known as human papillomavirus (HPV).

"MCV is another model that may increase our understanding of how cancers arise, with possibly important implications for non-viral cancers like prostate or breast cancer," said pathology professor Yuan Chang.