In March 1985, during routine investigation of hepatitis B (HB) case reports, an epidemiologist at the Long Beach (California) Department of Public Health noted that three HB patients had each received injections at the same weight-reduction clinic (clinic A) before disease onset. When review of previous case records and questioning of newly reported HB patients identified five additional HB cases among clinic attendees, the California Department of Health Services joined in the investigation of the clinic on July 1, 1985.

Clinic A belonged to a chain of 29 weight-reduction clinics located throughout southern California. Attendees at the clinics typically received a series of daily parenteral injections of human chorionic gonadotropin (HCG). Injections were usually given by jet injectors (Med-E-Jet Corp, Cleveland, Ohio), although some attendees received injections with single-use disposable needles and syringes. A standard regimen consisted of 30 injections; however, individuals varied considerably in duration of treatment and number of injections received.

The investigation focused on a cohort of 341 persons who attended clinic A during the first 6 months of 1985. Clinical history, review of risk factors for acquiring hepatitis B virus (HBV) infection, serologic testing for HBV markers (hepatitis B surface antigen (HBsAg), antibody to HB core antigen (anti-HBc), and IgM anti-HBc) and quantification of parenteral exposures at the clinic were obtained on 287 (84%) of cohort members. For comparison, 93 new attendees (after July 1, 1985) at clinic A and random samples of 100 prior attendees and 70 new attendees at the other Long Beach clinic (clinic B) were tested for markers of HBV infection.

Ultimately, 31 cases of clinical HB were identified among attendees of Clinic A (Figure 1). Onset dates ranged from January 1984 to November 1985, with the majority of cases occurring between February and November 1985. Only two (6%) of the patients with clinical HB had other identified risk factors for acquiring HBV infection in the 6 months before their illnesses.

The serologic study demonstrated that 21% of the cohort that attended clinic A between January 1, and July 1, 1985, had evidence of recent HBV infection, including 27 clinical and 33 subclinical (IgM anti-HBc positive) cases. In contrast, none of the 93 new attendees of clinic A had evidence of recent HBV infection (p 0.01). When all serologic markers of HBV infection were examined, 43% of the cohort that attended clinic A between January 1 and July 1 had evidence of HBV infection, compared with 7% of new attendees at clinic A; 8% of persons who attended clinic B on or before July 1; and 6% of persons who began attending clinic B after July 1.

On initial analysis of the cohort members, exposure to the jet injectors and HCG were both significantly associated with the development of acute HBV infection. However, two lots of HCG used at the clinic during the outbreak (from February 1985 onward) were negative when tested for HBsAg. Furthermore, stratification of cohort members who received HCG by type of parenteral inoculation (jet injector only, compared with syringe only) showed that 24% of those receiving injections by jet injector had developed acute HBV infection compared with none of those receiving injections by syringe only (p 0.01) (Table 1). These two groups had similar numbers of HCG exposures, with the syringe-only group averaging 31, while the jet injector-only group averaged 27.

Some patients at clinic A reported that they had sustained lacerations and bruising in the course of receiving the jet injections. Written protocols at clinic A specified that the Med-E-Jet injector nozzle be wiped with 70% isopropyl alcohol between injections, and that at the end of each day, the nozzle retaining cap and the tip be removed and disinfected. As an adjunct to this investigation, CDC conducted a series of in vitro and in vivo laboratory experiments to assess the potential for a contaminated Med-E-Jet to transmit HBV from patient to patient and to assess the potential for HBsAg contamination of this jet injector during actual use. After contaminating the nozzle tip of the jet injector with a known quantity (0.025 ml) of HBsAg-containing serum, the injector was fired into separate 1-dram vials (to simulate downstream transmission) and swab samples were taken of the exterior and interior surfaces of the nozzle. This procedure was repeated 10 times. A second set of experiments was conducted using the same procedure but with acetone swabbing to provide mechanical cleaning of the tip before discharge into the vials. In the first set of experiments (no acetone swabbing), HBsAg was found in 80% of the injection fluid vials and 87% of the swabs from the exterior and interior nozzle surfaces. Swabbing the contaminated tip of the Med-E-Jet with a cotton ball moistened in acetone did not significantly reduce the frequency with which HBsAg was found in any of these sites. However, the Med-E-Jet did not become contaminated during actual use when five injections were done on an HBsAg-positive chimpanzee. Bleeding did occur at the injection sites, even though injections were carefully done according to manufacturers recommendations.

The jet injectors were removed from use at clinic A on July 2. No cases have been identified among persons treated at clinic A after this date, and no cases associated with any of the other clinics in the chain have been identified to date. Both the manufacturer and the U.S. Food and Drug Administration have been informed of these findings. Reported by R Shah, MD, K Mackey, MPH, H Wallace, DrPH, K Yawata, Long Beach Dept of Public Health, R Roberto, MD, J Meissinger, MSPH, Infectious Disease Br, M Ascher, MD, S Hagens, MA, Viral and Rickettsial Disease Laboratory, J Chin, MD, State Epidemiologist, California Dept of Health Svcs; Div of Field Svcs, Epidemiology Program Office, Hepatitis Br, Div of Viral Diseases, Nosocomial Infections Laboratory Br, Hospital Infections Program, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: This is the first reported outbreak of any disease in which any kind of jet injector has been implicated as the vehicle of transmission. The CDC experiments reported here suggest that the Med-E-Jet, if contaminated, could transmit HBV but that it does not become contaminated easily during actual use. Once contaminated, however, the Med-E-Jet could not be easily cleaned by a simple swabbing technique, probably because of inaccessibility of contaminated surfaces of the nozzle tip and under the nozzle retaining cap. Furthermore, wiping the nozzle tip with a swab soaked in alcohol or acetone would not be expected to inactivate HBV. To ensure proper decontamination, disassembly and sterilization of the nozzle tip would be necessary.

Other investigators have attempted to assess the risk of HBV transmission by applying jet injections, using another model of jet injector, to two human chronic hepatitis B carriers and evaluating injection sites and the injection nozzle for contamination with HBsAg (1). All swab samples from injection sites and the exterior surface of the nozzle were negative for HBsAg. One other study, however, demonstrated transmission of the lactic dehydrogenase (LDH) virus between mice by subcutaneous jet injection with a Med-E-Jet (2). In the CDC studies, the estimated volume of contaminating material transferred in downstream injections was 0.53 ul (0.53 x 10))-3))ml). Therefore, it can be estimated that viruses that circulate in high titers in blood, such as HBV (10((8))/ml) and LDH virus (10((7))/ml), could be transferred during a procedure if gun contamination occurred. The probability of transferring microorganisms present in lower concentration ( 10((3))/ml) would be correspondingly lower.

The extensive transmission of HBV infection in this outbreak appears to have resulted from the unusual circumstance of multiple repeated jet gun injections in a cohort of patients. The initial likelihood of a highly infectious (HBeAg-positive) HBV carrier attending the clinic was low, but after initial disease transmission from such a carrier, patients incubating disease could serve as sources of infection for others, amplifying infection risk through several cycles and ultimately leading to high attack rates in the study cohort. Nevertheless, the magnitude of this outbreak can be explained only if the jet injector became contaminated repeatedly during use at the clinic.

Before this outbreak, virtually all epidemiologic observations have indicated that the jet-injector method of administering parenteral fluids, when properly done, is safe and effective. The current data suggest that, if this type of jet injector (Med-E-Jet) becomes contaminated with blood, disease transmission can occur and indicate a need for further assessments of the possibilities of disease transmission by other types of jet guns. Proper design of jet injectors to minimize risk of blood contamination of the nozzle tips, training in use of guns, and care in cleaning and disinfection if blood contamination occurs is necessary to ensure the continued safe use of these instruments.

References

1. Abb J, Deinhardt F, Eisenburg J. The risk of transmission of

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