Six people who underwent procedures at a clinic in Las Vegas, Navada, have been infected with the blood-borne hepatitis C virus and about 40,000 more should be tested for the virus, as well as for HIV, U.S. health officials said Wednesday.

Five of the people were treated the same day in late September at the Endoscopy Center of Southern Nevada; the sixth is believed to have been infected in July, the Southern Nevada Health District said in a statement.

An investigation found that "unsafe injection practices related to the administration of anesthesia medication might have exposed patients to the blood of other patients," the statement added.

Officials said the unsafe practices had been in place for several years and may have put others at risk. About 40,000 patients who received injections of anesthesia at the clinic will be told of the potential exposure in letters arriving next week.

Anyone who received anesthesia at the clinic from March 2004 to Jan. 11 should be tested for the virus, along with hepatitis B and HIV, chief health officer Lawrence Sands said.

"We are recommending all patients during this time frame to get tested because we cannot determine which patients may have been exposed," Sands said.

Hepatitis C is a chronic, potentially fatal virus that can cause liver ailments, including cancer and liver failure. The health district says it typically receives reports of two acute cases each year. Three of the six cases reported this year are acute, it said.

The virus may have been spread when clinic staff reused syringes and used a single dose of anesthesia medication on multiple patients, the district said.

(Agencies via Xinhua News Agency February 29, 2008)