LAS VEGAS, July 24 (UPI) -- Another hepatitis C case linked to a closed Las Vegas endoscopy clinic brings the number of confirmed cases of the disease to nine, health officials said.

However, the latest patient to test positive for the disease didn't become ill within a six-month incubation period, meaning the case is chronic, not acute, hepatitis C, the Las Vegas Review-Journal reported Thursday.

"This is an individual who was treated at the endoscopy center on one of two days,'' either July 25 and Sept. 21 of last year, said Jennifer Sizemore, a Southern Nevada Health District spokeswoman.

District and Centers for Disease Control and Prevention investigators said they think those are the dates nurse anesthetists transmitted hepatitis C to the six patients after contaminating single-dose anesthesia vials with reused syringes, the newspaper said.

In a report in May, Centers for Disease Control investigators reported one of the nurse anesthetists said reusing syringes and single-dose vials of a sedative reflected instructions the clinic staff received.

The outbreak was announced in February and led to the nation's largest patient notification, the newspaper said. About 50,000 patients were notified to be tested for hepatitis strains B and C and for HIV, the virus that causes AIDS.