The Ebola virus that has killed scores of people in Guinea this year is a new strain — evidence that the disease did not spread there from outbreaks in some other African nations, scientists report.

"The source of the virus is still not known," but it was not imported from nearby countries, said Dr. Stephan Gunther of the Bernhard Nocht Institute for Tropical Medicine in Hamburg, Germany.

He led an international team of researchers who studied the genetics of the virus and reported results online Wednesday in the New England Journal of Medicine.

The ongoing outbreak has caused panic and killed more than 120 people in West Africa, mostly in Guinea, according to the World Health Organization.

Ebola causes internal bleeding and organ failure and is fatal in 30 percent to 90 percent of cases, depending on the strain. It spreads through direct contact with infected people, and some earlier cases have been linked to certain fruit bats that live in West Africa.

There is no cure or vaccine, so containing the outbreak has focused on supportive care for those infected with the virus and isolating them to limit its spread.

Earlier, health officials had said the Guinea Ebola was a Zaire strain, different from the kind that has caused cases in other parts of Africa. The Democratic Republic of Congo used to be called Zaire.

The new research analyzed blood samples from 20 patients in the current outbreak and found the strain was unique.

"It is not coming from the Democratic Republic of Congo. It has not been imported to Guinea" from that country or from Gabon, where Ebola also has occurred, Gunther said.

Researchers think the Guinea and other strains evolved in parallel from a recent ancestor virus. The Guinea outbreak likely began last December or earlier and might have been smoldering for some time unrecognized. The investigation continues to try to identify "the presumed animal source," they write.

? eg ?H??.25pt;background:white'>But a number of women's groups — including the American Medical Women's Association and Our Bodies Ourselves — warn that moving to a DNA-based testing model would be a "radical shift" in medical practice that could lead to confusion, higher costs and overtreatment.

"It replaces a safe and effective well-established screening tool and regimen that has prevented cervical cancer successfully in the U.S. with a new tool and regimen not proven to work in a large U.S. population," state the groups in a letter to FDA Commissioner Dr. Margaret Hamburg. The letter, dated Monday, is signed by 17 patient advocacy groups, including Consumers Union, the Cancer Prevention and Treatment Fund and the National Alliance for Hispanic Health.

Chief among the advocates' concerns is that HPV-only testing could lead to overtreatment of younger women who carry the virus but have little risk of developing actual cancer. Most sexually active young people will contract HPV, though their bodies usually eliminate the virus within a few months. Only years-long infections develop into cancer.

"Unfortunately the HPV test by itself isn't very useful because so many young women have HPV that will disappear without any treatment," said Diana Zuckerman of the Cancer Prevention and Treatment Fund. "Having an HPV test without also getting a Pap smear to check for problems is going to scare a lot of women who are not developing cervical cancer."

An FDA spokeswoman said the agency could not comment on the letter since it deals with a product under review.

For decades the Pap test was the only screening option for cervical cancer — and it's had a remarkably successful track record. The number of cervical cancer cases reported in the U.S. has decreased more than 50 percent in the past 30 years, primarily due to increased Pap screening. Still, an estimated 12,000 cases of cervical cancer are expected to be diagnosed this year, a fact that has spurred development of genetic tests like the one from Roche and other test makers.

Medical guidelines have been evolving rapidly to try and incorporate both techniques. Under the latest guidelines from the American Cancer Society, a Pap test is recommended every three years for women 21 to 29 years old. Women 30 and older should have both a Pap test and an HPV test every five years, or a Pap test alone every three years. Women who have had an HPV vaccine should still follow screening guidelines.

HPV screening is not recommended for women in their 20s because it increases the odds of more invasive testing that can leave the cervix less able to handle pregnancy later in life.

But Roche is seeking FDA approval to market its test to women age 25 and up.

That approach was endorsed unanimously last month by a panel of FDA advisers who voted 13-0 that Roche's cobas HPV test appears safe and effective as a first-choice screening tool. The FDA is weighing that recommendation as it considers approval the company's application.

Despite the overwhelming endorsement, patient advocates say FDA approval would fly in the face of current medical guidelines, none of which recommend testing with HPV alone for younger women. They point out that the U.S. Preventive Services Task Force, which sets federal medical guidelines, gave HPV testing a "D'' rating in women under age 30, warning that testing could lead to "unnecessary treatment and the potential for adverse pregnancy outcomes."

Even physicians who support HPV testing as an important option warn that introducing a DNA-only testing regimen may lead to confusion that disrupts care. The American College of Obstetricians and Gynecologists says many physicians are already confused by the two existing testing options: Pap alone or Pap with HPV testing.

"Introducing a third screening alternative will likely further increase confusion, and the risk to women of getting either over or under screened," the group said in comments at the FDA meeting last month. The group, which represents 57,000 U.S. obstetricians and gynecologists, did not sign the letter sent to FDA this week.

Finally there is the cost. An HPV test costs between $80 and $100, at least twice as much as a $40 Pap. And under Roche's proposal, women who test positive for HPV would be referred for colposcopy, a more invasive testing procedure that can cost up to $500.

All these factors have consumer advocates urging the FDA to break from its advisers and deny first-choice status to the Roche test.

"Sometimes the FDA overrules the advisory committee and it's OK," said Dr. Susan Wood, a former FDA official who now directors the Jacobs Institute of Women's Health.