From April through August 1994, outbreaks of hepatitis B virus (HBV) infection occurred in five chronic hemodialysis centers in California, Nebraska, and Texas. This report summarizes investigations by state and local public health officials and CDC, which suggest that transmission of HBV from hemodialysis patients with chronic HBV infection to susceptible patients resulted from failure to identify and isolate HBV-infected patients during hemodialysis; sharing of staff, equipment, and supplies among patients; and failure to vaccinate susceptible patients against hepatitis B.

In these investigations, a case of acute HBV infection was defined as seroconversion from hepatitis B surface antigen (HBsAg)-negative to HBsAg-positive in a hemodialysis patient during the exposure period defined in each investigation. A susceptible patient was defined as a hemodialysis patient who was negative for HBsAg, antibody to HBsAg (anti-HBs), and antibody to hepatitis B core antigen (anti-HBc). An immune patient was defined as a patient who was positive for anti-HBs as a result of vaccination or positive for anti-HBc and/or anti-HBs as a result of natural infection. A patient with chronic HBV infection was defined as any patient who was positive for HBsAg for greater than 6 months or was positive for both HBsAg and anti-HBc (immunoglobulin M negative).

Hemodialysis Center A, Texas

From April 1 through May 18, 1994, cases of acute HBV infection were identified through routine seroscreening in 14 (70%) of 20 patients at center A, which opened in January 1994. In addition, a case of previously unrecognized chronic HBV infection was identified in a patient who had received hemodialysis nine times at center A from January 26 through February 9, but had not been isolated from other patients during these treatments. All case-patients had shared at least one shift with the patient with chronic infection; however, no single event, day, or shift was associated with transmission to all cases. The source-patient had been transferred from another center where he was known to have chronic infection, but his serologic status had not been reviewed on admission to center A. In addition, although all patients at center A were screened monthly for HBsAg, results were not reviewed routinely. The investigation also indicated that staff frequently handled blood-contaminated items without changing gloves or washing hands and that clean and contaminated supply areas were adjacent to each other. Less than 20% of the patients at center A had been vaccinated against hepatitis B; no cases were detected among those who had been vaccinated.

Hemodialysis Center B, California

From April 1 through June 1, 1994, cases of acute HBV infection were identified in seven (5.3%) of 131 susceptible patients in center B. Of the two patients with chronic infections, one was identified as the source of the transmission through genetic sequencing of virus isolates from all infected patients.

Staff frequently were assigned to provide simultaneous care for the source-patient with chronic infection and for susceptible patients. Common medication/supply carts were moved between stations, and medications and supplies were shared among infected and susceptible patients. Staff had been shared among the implicated source-patient, who received heparin, and two susceptible patients, of whom one received heparin and became infected; the other susceptible patient did not receive heparin and was uninfected. Partially used heparin vials routinely were returned to a common medication cart. A cohort study indicated that HBV infection was associated with a single shift (relative risk {RR}=7.0; 95% confidence interval {CI}=1.5- 42.8) -- the shift following that during which staff had been shared among susceptible patients and the source-patient. In addition, all of the infected patients on that shift had been at stations clustered in one area of the unit. Because one heparin vial probably had been shared among these patients, contamination of a shared multiple-dose vial was considered the most likely route of HBV transmission among patients in this outbreak. Of all patients in center B, none had been vaccinated against hepatitis B.

Hemodialysis Center C, California

Center C opened on April 6, 1994. Based on routine serologic screening during June 13-August 15, seroconversion to HbsAg positivity occurred in four (9.5%) of 42 susceptible patients, including two in June, one in July, and one in August. One patient known to have chronic infection had been dialyzed in an isolated area since the center opened. Although this patient had the same HBsAg subtype as the cases, he was hepatitis B e antigen (HBeAg)-negative, suggesting he had not been the source. Two patients with chronic infection had been admitted to center C on June 20 and 27 (following seroconversion in the first two cases). Risk for infection was not associated with a single event, day, shift, or geographic clustering, and infection-control practices were considered appropriate. All staff were negative for HBsAg, and no patients had been vaccinated against hepatitis B. Based on a cohort study, risk for acute infection was associated only with receipt of hemodialysis as a patient at a community hospital any time during April 1-21 (RR=9.0; 95% CI=1.1-76.0). Limited results of HBV testing of all patients receiving hemodialysis at that hospital precluded determining a source of infection in the hospital hemodialysis setting.

Hemodialysis Center D, California

From June through August 1994, cases of acute HBV infection were identified in 11 (14%) of 77 susceptible patients at center D. Monoclonal antibody subtyping of HBV isolates from two of three patients with chronic infections and seven of the 11 cases identified two distinct antigen subtypes (adw2 and adw4). Isolates from four cases were subtype adw2; stations at which these patients were treated were clustered geographically, and equipment, supplies, and hemodialysis staff had been shared among these patients and the two patients with chronic infections who also had subtype adw2 infections. The three other cases were infected with subtype adw4; although these patients were not treated at clustered stations, their care entailed shared equipment, supplies, and staff. One of these patients seroconverted 1-2 months before the others; however, the source of this patient's infection was unknown. No patients had been vaccinated against hepatitis B.

Hemodialysis Center E, Nebraska

From March through June 1994, cases of acute HBV infection were identified in two (0.7%) of 303 patients at center E. A patient known to have a chronic HBV infection had been admitted to center E in December 1993. The first case became HBsAg-positive in March 1994; this patient had been hemodialyzed on the same shift and shared staff with the patient with chronic infection on two occasions before seroconversion. The second case became HBsAg-positive in June 1994; this patient had been hemodialyzed on the same shift and had shared staff with the first case-patient on two occasions before seroconversion. The same HBsAg subtype (adw2) was present in the patient with chronic infection and two cases. None of the patients had been vaccinated against hepatitis B.

Reported by: K Hendricks, MD, L Sehulster, PhD, Infectious Disease Epidemiology and Surveillance Div; RL Bell, PhD, J Cousins, W MacNeeley, A Payne, M des Vignes Kendrick, MD, City of Houston Dept of Health and Human Svcs; D Simpson, MD, State Epidemiologist, Texas Dept of Health. M Tormey, MPH, A Itano, MSPH, L Mascola, MD, Los Angeles County Health Dept, Los Angeles; D Vugia, MD, J Rosenberg, MD, Div of Communicable Disease Control, S Waterman, MD, State Epidemiologist, California Dept of Health Svcs. TJ Safranek, MD, State Epidemiologist, Nebraska Dept of Health. Hospital Infections Program and Hepatitis Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases , CDC.

Editorial Note

Editorial Note: HBV is present in extraordinarily high titers in blood and other body fluids of infected patients ( greater than or equal to 10 superscript 9 virus particles per milliliter). Because the virus survives well in the environment, blood-contaminated surfaces that are not routinely cleaned and disinfected represent a reservoir for transmission of HBV (1). Dialysis staff can transfer virus to patients from contaminated surfaces by their hands or through use of contaminated equipment and supplies.

All five outbreaks of HBV infection in chronic hemodialysis centers described in this report were associated with failure of the facilities to adhere to one or more of the recommended infection-control practices for preventing the transmission of HBV and other bloodborne pathogens in such settings. Previous reports consistently have indicated that risk factors associated with HBV transmission among patients in hemodialysis centers include the presence of a patient with chronic HBV infection and failure to isolate such patients by room, machine, and staff (2-4). These reports also have documented that physical separation of HBV-infected patients from susceptible patients substantially reduces the risk for HBV transmission.

Recommendations for infection-control practices were published and disseminated initially in 1977 (5); hepatitis B vaccination has been recommended for susceptible patients since 1982. In 1977, the national incidence of HBV infection among hemodialysis patients was 3.0%; by 1980, the national incidence had declined to 1.0%, and by 1989, to 0.1% (2).

To prevent transmission of bloodborne pathogens in general health-care settings, universal precautions were initially recommended in 1985 and updated in 1988 (6); the recommendations emphasized the use of barriers (e.g., gowns, gloves, and eyewear) and adherence to routine hand washing, appropriate disposal of needles and other sharp instruments, and disinfection and sterilization procedures. To prevent transmission of bloodborne pathogens in hemodialysis settings, both universal precautions and the following hemodialysis-specific infection-control practices recommended in 1977 should be used: 1) Serum specimens from all susceptible patients should be tested monthly for HBsAg, and these results should be reviewed promptly. 2) HBsAg-positive patients should be isolated by room, machine, instruments, medications, supplies, and staff. 3) Instruments, medications, and supplies should not be shared between any patients. When sharing of multidose medication vials is necessary, medications must be prepared in a clean centralized area separate from areas used for patient care, laboratory work, or refuse disposal. 4) Routine cleaning and disinfection procedures should be followed, including clear separation of areas established to handle clean and contaminated items. Blood specimens should be handled with gloved hands and stored in designated areas away from medication preparation or central supply areas.

Hepatitis B vaccine has been recommended for all susceptible hemodialysis patients since it became available in 1982 (7). However, by 1993 only 29% of hemodialysis patients in the United States had been vaccinated (2). In 1993, vaccination coverage among patients in the southern California region was 13%, lower than in northern California or any other state in the United States (2). Among immunocompetent persons, a protective antibody response develops in 90%-95% of vaccine recipients, protection against HBV infection persists even when antibody titers subsequently decline, and booster doses are unnecessary (7). In contrast, the proportion of vaccinated hemodialysis patients who develop a protective antibody response is lower (50%-60%), and booster doses are necessary to maintain protection against hepatitis B when antibody titers decline below protective levels (7,8). However, greater than or equal to 50% of hemodialysis patients can be protected from hepatitis B by vaccination, and maintaining immunity among these patients will reduce the frequency and costs of serologic screening (9,10).

References

1. Favero MS, Maynard JE, Peterson NJ, et al. Hepatitis B antigen on environmental surfaces. Lancet 1973;2:1455.

2. Tokars JI, Alter MJ, Favero MS, Moyer LA, Miller E, Bland LA. National surveillance of dialysis-associated diseases in the United States, 1993. Am Soc Artif Intern Organs J 1996 (in press).

3. Niu MT, Penberthy LT, Alter MJ, Armstrong CW, Miller GB, Hadler SC. Hemodialysis-associated hepatitis B: report of an outbreak. Dialysis & Transplantation 1989;18:542-6,555.

4. Alter MJ, Ahtone J, Maynard JE. Hepatitis B virus transmission associated with a multiple-dose vial in a hemodialysis unit. Ann Intern Med 1983;99:330-3.

5. CDC. Hepatitis-control measures for hepatitis B in dialysis centers. In: Hepatitis surveillance report no. 41. Atlanta, Georgia: US Department of Health and Human Services, Public Health Service, CDC, 1977:12-7.

6. CDC. Update: universal precautions for prevention of transmission of human immunodeficiency virus, hepatitis B virus, and other bloodborne pathogens in health-care settings. MMWR 1988;37:377-82,387-8.

7. CDC. Hepatitis B virus: a comprehensive strategy for eliminating transmission in the United States through universal childhood vaccination -- recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1991;40(no. RR-13).

8. Stevens CE, Alter HJ, Taylor PE, et al. Hepatitis B vaccine in patients receiving hemodialysis: immunogenicity and efficacy. N Engl J Med 1984;311:496-501.

9. Moyer LA, Alter MJ, Favero MS. Hemodialysis-associated hepatitis B: revised recommendations for serologic screening. Seminars in Dialysis 1990;3:201-4.

10. Alter MJ, Favero MS, Francis DP. Cost benefit of vaccination for hepatitis B in hemodialysis centers. J Infect Dis 1983;148:770-1.

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