LAS VEGAS – A hepatitis C outbreak that prompted the largest public health notification operation in U.S. history has been traced to two patients treated at a Las Vegas endoscopy clinic in 2007, and officials said Thursday that clinic workers knew at least one carried the virus before treatment.

Brian Labus, a senior Southern Nevada Health District epidemiologist, told the district board on Thursday that clinic staff members reused syringes and vials of medicine despite knowing that one patient had hepatitis C, which spread the blood-borne liver disease from patient to patient.

“We know now the chain of transmission,” Labus told The Associated Press as he prepared his presentation to the board. “We know where the virus came from and where it went. We're starting to get a better understanding of what happened at the clinic.”

He said individual patients' identities and information about their treatment would not be made public for health privacy reasons.

“It is important for us to remember that this outbreak is not the result of any actions on the part of the patients, but it is the result of unsafe practices by the staff of these clinics,” Dr. Lawrence Sands, district chief health officer, said in a statement.

DNA tests traced the spread of the incurable virus to people treated July 25, 2007, and Sept. 21, 2007, at the Endoscopy Center of Southern Nevada.

District spokeswoman Jennifer Sizemore said the source patient treated in September was known to be carrying the hepatitis C virus and clinic staff may have known the source patient treated in July was similarly infected, though health officials aren't sure.

Health officials earlier identified the months of July and September when they began notifying 53,000 former clinic patients Feb. 27 to get blood tests to check for hepatitis B, C and HIV, the virus that causes AIDS.

On Wednesday, district officials linked an eighth case of hepatitis C to the Endoscopy Center of Southern Nevada. A ninth case in the outbreak has been traced to an affiliated clinic, the Desert Shadow Endoscopy Center in Las Vegas. The totals don't reflect the two source patients because they had contracted the virus earlier, Sizemore said.

Both outpatient facilities were headed by Dr. Dipak Desai, a member of the Nevada Board of Medical Examiners from 1993 to 2001, and former chairman of the board's investigative committee. Desai has surrendered his license to practice medicine in Nevada pending the results of hepatitis investigations and a Sept. 8 hearing before the board.

Health district officials have said 77 more people contracted hepatitis while being treated at the Endoscopy Center from March 2004 to last Jan. 11. But investigators could not conclusively link those cases to procedures at the clinic.

In all, some 400 former patients of the center tested positive for hepatitis C but officials have determined that most could have contracted the virus through other means, including intravenous drug use, blood transfusions, organ transplants, kidney dialysis, receiving blood clotting agents before 1987, or sexual contact with a person with hepatitis C.

Sands said 6,000 people have enrolled in a hepatitis C exposure registry that the district established in June.

“We are very encouraged by participation in the registry,” Sands said. “Patients are providing us with important information about their procedures, their test results, and health status. The registry will allow us to identify additional cases or exposures at either clinic.”

Hepatitis C results in the swelling of the liver and can cause stomach pain, fatigue and jaundice. It may eventually result in liver failure. Even when no symptoms occur, the virus can slowly damage the liver.

Earlier this week a Nevada judge ruled that patients who were treated at the clinic but weren't made ill can claim emotional distress in a class-action lawsuit. The clinic currently faces 121 lawsuits in Clark County District Court in Las Vegas.

Associated Press writer Oskar Garcia contributed to this report.

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