A newly discovered virus may play a role in the development of Merkel cell carcinoma, a rare and lethal skin cancer that afflicts mainly the elderly and those with weak immune systems, according to a study in the latest edition of the journal Science.

The germ, Merkel cell polyomavirus, was uncovered in 80 percent of cancerous tumors and 8 percent of comparison tissue. Another analysis suggested the cells were infected before they became cancerous, showing the virus may be involved in the process, the researchers said.

More study is needed to confirm the findings and clarify details about the virus, a type tied to cancer in animals, the researchers said. If confirmed, it would be the eighth cancer-causing virus in humans, joining others such as the sexually transmitted human papillomavirus tied to cervical cancer.

"This is actually the beginning of a long process because there are so many things that can be done now that we have a target," said Patrick Moore, a professor of microbiology and molecular genetics at the University of Pittsburgh School of Medicine, in a telephone interview. "Within the next couple of years, I would hope there would be a test that would help diagnose infection with this virus and that we could target treatment against this virus."

Mr. Moore led the project with his wife, Yuan Chang, a professor of pathology at the university. In 1993, the two identified the herpes virus that causes Kaposi's sarcoma, a cancer common in Africa and among patients with weakened immune systems.

The researchers chose to focus on Merkel cell carcinoma in their hunts for cancer-causing germs because it also generally affects those with compromised immune systems and the elderly, a group vulnerable to viruses. About 1,500 Americans are diagnosed each year with the condition, one of the most aggressive forms of skin cancer. Half of those patients with advanced disease die within nine months.

The scientists searched through the DNA of cells affected with the cancer and identified Merkel cell polyomavirus, or MCV, with a genetic sequence similar to a known virus.

"Now we need to find out how it works," Ms. Chang said. The virus could produce a protein that spurs cancer or blocks a gene that suppresses tumors, she said.