CDC mulled other theories in Vegas HCV outbreak
77 more HCV cases now being investigated
Centers for Disease Control and Prevention investigators considered several other theories before concluding that improper needle practices and reuse of single-dose vials of propofol likely caused a recent HCV outbreak among patients at a Las Vegas endoscopy clinic. The outbreak led to the largest "look-back" notification in history, as some 40,000 patients were advised to be tested for hepatitis C and B, as well as HIV.
The CDC officially has confirmed six cases, citing "inappropriate reuse of syringes [and] . . . use of medication vials intended for single-person use on multiple persons" as the most likely source of transmission.1
Since the initial report, the Southern Nevada Health District had identified 77 additional HCV-infected patients that are "potentially linked" to the Endoscopy Center of Southern Nevada. Health investigators also reported a separate HCV case that appears to involve transmission at another Las Vegas clinic, the Desert Shadow Endoscopy Center. "While it has been determined this acute case is linked to the center there is not sufficient information at this time to determine the likely source of disease transmission," the state health officials reported.
Concerning the original investigation into the practices at the Endoscopy Center of Southern Nevada, a May 15, 2008, "trip report" by CDC investigators reveals the agency looked at transmission via endoscopy equipment and considered the possibility that an infected clinician was raiding the drug supply. The latter theory fell down the list rather quickly because no HCV-positive clinic worker was identified. "Transmission of HCV from infected staff has occasionally been reported zand typically involved diversion of narcotics such as fentanyl," the CDC investigators reported. "This route of transmission appears unlikely in the clinic setting given that no staff members have tested positive for HCV infection and propofol is not a commonly abused medication."
Observation of anesthesia administration practices indicated that some staff routinely reused syringes during individual procedures to withdraw anesthesia from single-use propofol vials that were inappropriately used to provide medication for multiple patients, the CDC reported. "Similar practices have previously been implicated in the transmission of bloodborne pathogens," investigators noted. Another possible route that was considered was inadequate endoscope reprocessing.
"Occasionally, patient-to-patient HCV transmission has been attributed to inadequate cleaning or disinfection of patient equipment, but we consider this mechanism less likely in the context of our investigation," the investigators reported.
In the clinic, endoscope reprocessing procedures were generally followed, except that enzymatic cleaning solution was used on more than one endoscope. Manual cleaning with brushes to remove biofilms and high-level disinfection, which are considered most important for reducing potential bloodborne pathogen transmission, were judged adequate, the report notes. "However, because recordkeeping was lacking in some respects, we could not determine whether endoscopes had been processed at the same time or by the same machine (this was not recorded in the charts)," the investigators concluded.
On Sept. 21, 2007, — the day five of the six confirmed HCV cases were at the clinic — patient records indicated that two of the case-patients had procedures performed with one particular endoscope. However, the "clinic staff attributed this to a clerical error," the CDC reported. "In addition, in [previous outbreaks], endoscopic biopsies were found to be an independent risk factor for HCV infection, (though deficiencies in the handling of parenteral medications were also noted)," the report concludes. "In our investigation, only three of six clinic-associated case-patients had a biopsy done, and the needle used was reported to be a single-use disposable item."
Reference
- Centers for Disease Control and Prevention. Acute hepatitis C virus infections attributed to unsafe injection practices at an endoscopy clinic — Nevada, 2007. MMWR 2008; 57; 513-517.
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