Nevada hepatitis C outbreak largest in U.S.

By Mary Manning

Thursday, Oct. 23, 2008 | 10:25 a.m.

The Southern Nevada Health District has classified 105 cases of chronic hepatitis C infection as possibly associated with two endoscopy centers in Las Vegas, making it the largest outbreak of the blood-borne illness in the country.

Another nine hepatitis C cases have been directly linked to two endoscopy centers in Las Vegas, bringing the total number of cases revealed in the investigation to 114, said Brian Labus, epidemiologist for the Southern Nevada Health District.

The second largest outbreak of 99 hepatitis C infections occurred in 2003 at a Nebraska cancer clinic where a doctor was accused of using unsanitary practices between March 2000 and December 2001. One of those patients died.

None of the Southern Nevada patients has died.

"Nevada is now No. 1," Labus said. "Maybe now we can be No. 1 in patient safety."

Since the local investigation began in January, Southern Nevada health officials have notified 53,000 people, asking them to enroll in the health district's Hepatitis C Exposure Registry, which began in June, but only 7,331 have done so thus far. That's a response rate of less than 14 percent.

The Endoscopy Center of Southern Nevada at 700 Shadow Lane accounted for seven of the cases tied to the outbreak. Two other cases were linked to the Desert Shadow Endoscopy Center at 4275 Burnham Ave. Both clinics have been closed.

Of those cases "posssibly associated" with the centers, 101 cases were discovered at the Shadow Lane clinic and four at the Burnham Avenue facility, Labus said. He reported the new findings to a monthly meeting of the Southern Nevada Health District Board. That number increased from 77 in July.

Patients who had laboratory-confirmed cases of hepatitis C, verified procedures done at either of the two clinics, no identified risk factors and no history of positive laboratory reports have been classified as "possibly associated" with the clinics involved in the outbreak.

The health district classified 35 laboratory-confirmed cases of the illness as "indeterminate" if a patient reported one or more risk factors associated with hepatitis C infections. This classification does not rule out possible infection at the clinics. However, the health district cannot make any further determination because other likely sources of infection exist.

Labus and his staff evaluated chronic hepatitis C infections by examining a patient's risk over a lifetime. Evaluating acute hepatitis C infections involved examining a patient's risk for six months before the onset of symptoms. To evaluate patients' risk factors and to determine if their infections were related to one of the clinics, the health district developed a set of criteria to classify cases based on whether they were chronic or acute. In addition, classifications concerning the likelihood that the patient was exposed at a clinic were developed to help investigators better understand patient risk factors.

"The registry, the interviews and the criteria developed to identify and classify cases provided the investigators with important information to help us better understand the scope of this outbreak," chief health officer Dr. Lawrence Sands said. "This is the largest disease investigation that our health district has undertaken and we recognize the importance of sharing these results with the community."

In July the health district reported that it had identified two source cases related to the Endoscopy Center of Southern Nevada outbreak. One patient had a procedure on July 25, 2007. The other had a procedure on Sept. 21, 2007. These are the dates that disease transmission were known to occur.

"The identification of these additional cases as well as the identification of the source cases from July and September reinforces our longstanding recommendation for patients of the clinic to get tested for possible infections," Sands said.

Labus said that he expects a few more cases to emerge as he prepares a final report on the outbreak, "but not a hundred."

The health district, state health officials and investigators from the Centers for Disease Control and Prevention began a massive effort to reach patients who may have been exposed to hepatitis B, hepatitis C or HIV from reuse of syringes, using single-dose bottles of anesthesia on multiple patients and in some cases failing to clean equipment thoroughly between patients at the clinics.

Results of genetic testing allowed the health district's epidemiology team to positively identify the two individuals as the source cases among clusters of patients who underwent procedures on the same dates. Samples were tested by the Centers for Disease Control and Prevention.

More hepatitis C information on the outbreak, including the health district's interim report, is available at www.SouthernNevadaHealthDistrict.org.