Case-control study of hepatitis B and hepatitis C in older adults: Do healthcare exposures contribute to burden of new infections?§


  • Potential conflict of interest: Nothing to report.

  • Primary support for this investigation was provided by the Division of Viral Hepatitis, Centers for Disease Control and Prevention; staff were funded by their primary institutions.

  • §

    Meeting at which portions of this work were presented: Fifth Decennial International Conference on Healthcare-Associated Infections, Atlanta, GA, March 18-22, 2010.

  • The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.


Reports of hepatitis B virus (HBV) and hepatitis C virus (HCV) transmission associated with unsafe medical practices have been increasing in the United States. However, the contribution of healthcare exposures to the burden of new infections is poorly understood outside of recognized outbreaks. We conducted a case-control study at three health departments that perform enhanced viral hepatitis surveillance in New York and Oregon. Reported cases of symptomatic acute hepatitis B and hepatitis C occurring in persons ≥55 years of age from 2006 to 2008 were enrolled. Controls were identified using telephone directories and matched to individual cases by age group (55-59, 60-69, and ≥70 years) and residential postal code. Data collection covered exposures within 6 months before symptom onset (cases) or date of interview (controls). Forty-eight (37 hepatitis B and 11 hepatitis C) case and 159 control patients were enrolled. Case patients were more likely than controls to report one or more behavioral risk exposures, including sexual or household contact with an HBV or HCV patient, >1 sex partner, illicit drug use, or incarceration (21% of cases versus 4% of controls exposed; matched odds ratio [mOR] = 7.1; 95% confidence interval [CI]: 2.1, 24.1). Case patients were more likely than controls to report hemodialysis (8% of cases; mOR = 13.0; 95% CI: 1.5, 115), injections in a healthcare setting (58%; mOR = 2.7; 95% CI: 1.3, 5.3), and surgery (33%; mOR = 2.3; 95% CI: 1.1, 4.7). In a multivariate model, behavioral risks (adjusted OR [aOR] = 5.4; 95% CI: 1.5, 19.0; 17% attributable risk), injections (aOR = 2.7; 95% CI: 1.3, 5.8; 37% attributable risk), and hemodialysis (aOR = 11.5; 95% CI: 1.2, 107; 8% attributable risk) were associated with case status. Conclusion: Healthcare exposures may represent an important source of new HBV and HCV infections among older adults. (HEPATOLOGY 2013)

Hepatitis B virus (HBV) and hepatitis C virus (HCV) are both transmitted by exposure to infectious blood. These viruses are the two most prevalent bloodborne pathogens in the United States, with an estimated 1.4 million persons chronically infected with HBV and an estimated 3.2 million persons chronically infected with HCV.1-3 As the incidence of new infections with these viruses has declined over the past several decades, evidence has emerged that the epidemiology has changed as well. For example, older age groups account for a growing proportion of the total number of acute hepatitis B cases reported to the Centers for Disease Control and Prevention (CDC); by 2008, persons ≥50 years of age represented 24% of total cases, compared with 16% in 1999.4 Likewise, in 2008, persons ≥50 years represented 21% of all acute hepatitis C cases reported to the CDC.4 Surveillance for viral hepatitis is important to target primary prevention measures (e.g., preexposure vaccination for HBV) and to control the spread of infection when new cases are identified.3-7


aOR, adjusted odds ratio; CDC, Centers for Disease Control and Prevention; CI, confidence interval; HBV, hepatitis B virus; HCV, hepatitis C virus; mOR, matched odds ratio.

Healthcare-associated transmission of HBV and HCV in the United States was previously recognized in association with occupational exposures and unscreened blood transfusions, but was considered uncommon in recent decades.8-10 However, reports of viral hepatitis outbreaks resulting from lapses in infection control practices have been increasing, particularly in ambulatory care settings, which tend to have less oversight and fewer resources for infection control.10-12 Increased delivery of healthcare in outpatient settings has been driven, in part, by cost-containment initiatives and the aging of the U.S. population.13 As a group, older persons tend to have more exposure to healthcare settings and fewer behavioral risks (e.g., injection drug use) for acquiring acute hepatitis B or hepatitis C, compared with younger persons. This is illustrated by data on acute hepatitis C cases from 2007, which showed that the percentage of patients reporting injection drug use was 28% among persons ≥40 years, compared with 57% among younger persons; conversely, surgery was reported more frequently in the older age group (32% versus 13%).7 A similar pattern is observed for acute hepatitis B.7 We hypothesized that healthcare-related exposures result in sporadic transmission of HBV and HCV infections, outside of recognized outbreaks. Furthermore, we hypothesized that the contribution of such exposures to the incidence of acute hepatitis B and hepatitis C in the United States likely increases with age, such that this effect would be more pronounced (and more readily detectable) among older age groups (e.g., persons ≥55 years). Therefore, we sought to examine the contribution of healthcare exposures outside of recognized outbreaks among cases of acute hepatitis B and hepatitis C reported among older adults by conducting a case-control study in sites that perform enhanced viral hepatitis surveillance.4, 6

Materials and Methods

We conducted a case-control study to examine risk factors for acute hepatitis B and C. Three health departments (located in New York City, New York State, and Oregon) conducted enrollment, interviews, and related data collection for persons reported with acute hepatitis from 2006 to 2008. Confirmed symptomatic cases of acute hepatitis B and acute hepatitis C, with laboratory and clinical criteria that met the standardized CDC surveillance case definitions and occurred in persons ≥55 years, were eligible for enrollment.14, 15 Incarcerated persons, nursing home residents, and cases identified through outbreak investigations were excluded. Three controls per case were targeted for enrollment. The initial aim was to recruit 44 cases with 3 matched controls per case. We calculated this sample size with an alpha error of 0.05 and 80% power to detect a 3-fold difference in proportions between cases and controls, assuming a prevalence of 10% exposure among control subjects.16

Controls were matched to cases by age group (55-59, 60-69, and ≥70 years) and postal code of residence. Potential controls were selected from the general population using random selection of residential telephone numbers from internet-based reverse look-up directories. Advance letters were sent to selected households, with subsequent telephone screening against the applicable age requirements. Exclusion criteria for controls included residence in a nursing home, history of HBV or HCV infection, or lifetime history of hepatitis B vaccination.

The study protocol was approved by the institutional review boards at the CDC and the participating health departments. Case patients and control subjects were contacted by telephone and provided verbal informed consent before enrollment. Data, including behavioral and healthcare-related exposures that occurred in the 6 months before symptom onset (cases) or before the date of interview (controls), were collected from consenting study participants. To confirm reported exposures and identify healthcare encounters not reported during participant interviews, we also sought additional informed consent from participants to review their medical records. Information from medical charts was abstracted using a standardized form for the subset of participants that gave their consent.

Healthcare encounter data from participant interviews were examined to identify potential contradictory responses. For example, 9 (4%) participants indicated they had undergone cardiac catheterization or colonoscopy, but also reported they had not received anesthesia. In these instances, available information was reviewed in detail, and, where deemed appropriate (i.e., where it was unlikely an invasive procedure was performed without sedation or anesthesia), data were changed to indicate that the participant did receive anesthesia. In addition, data were changed in instances where medical chart review was performed and identified procedures that participants had not reported or indicated that a reported procedure actually occurred outside the relevant 6-month exposure period. These changes were recorded in a separate dataset and analyzed separately from the dataset that contained unaltered interview responses.

Demographic information for eligible cases was used to compare enrolled and nonenrolled cases. Univariate measures of association were obtained using chi-square and Fisher's exact tests. Adjusted measures of association comparing cases and their matched controls were obtained using multivariate conditional logistic regression models. A composite variable representing behavioral risk exposures was included in multivariate models, along with healthcare encounters that were found to be associated with hepatitis B or C infection using matched univariate analysis (P ≤ 0.1) and reported by more than 10% of cases. Dental procedures, blood transfusions, and healthcare encounters that do not identify a specific healthcare procedure (e.g., overnight hospital stay or emergency room visit) were not included in multivariate models. A second multivariate model was constructed using interview data that were changed after medical chart review. A third model containing only acute hepatitis B cases and their matched controls was also constructed. Data were analyzed using SAS version 9.1 (SAS Institute Inc., Cary, NC). Population-attributable risks were calculated for exposures that were independently associated with acute hepatitis B or C infection in the multivariate models.17


A total of 71 cases of acute hepatitis B and acute hepatitis C among noninstitutionalized individuals 55 years or older were identified from 2006 to 2008 by the three participating health departments. Two additional cases were deemed ineligible because they occurred in institutionalized persons: one in a correctional facility and the other in a long-term care facility. Fifty-eight (82%) of the seventy-one eligible cases were acute hepatitis B, and 13 (18%) were acute hepatitis C. Fifty-nine (83%) cases were identified in New York and 12 (17%) in Oregon (Table 1). Of the 71 cases identified, 48 (68%) were enrolled in the study. Of the 23 cases not enrolled, 13 (57%) declined to participate in the study, 7 (30%) were lost to follow-up (i.e., after being interviewed to complete the standard surveillance case report form), and 3 (13%) were unable to consent (e.g., because of a language barrier). Enrolled and nonenrolled cases were not significantly different with regard to age category, study site, sex, race or ethnicity, and acute hepatitis diagnosis (Table 1). It was not possible to calculate the overall participation rate among controls because telephone screening of potential controls was terminated in many instances before it could be determined whether any household members met the age requirements for case matching. However, participation was 60% among potential controls who were successfully contacted and indicated that they met the age criteria.

Table 1. Demographic Characteristics of Eligible Hepatitis B and Hepatitis C Cases, by Enrollment Status*
CharacteristicEnrolled Cases (%)Cases Not enrolled (%)Total (%)P
  • *

    Cases with missing or unknown information excluded.

  • New York State Department of Health enhanced viral hepatitis surveillance program included 57 counties, outside of the five counties that comprise New York City.

Age category
55-5910 (20.8)9 (39.1)19 (26.8)0.264
60-6925 (52.1)9 (39.1)34 (47.9) 
70+13 (27.1)5 (21.7)18 (25.4) 
New York (state)21 (43.8)8 (34.8)29 (40.9)0.497
New York City18 (37.5)12 (52.7)30 (42.3) 
Oregon9 (18.8)3 (13.0)12 (16.9) 
Male32 (66.7)15 (65.2)47 (66.2)0.904
Female16 (33.3)8 (34.8)24 (33.8) 
White34 (70.8)11 (50.0)45 (63.4)0.091
Non-white14 (29.2)11 (50.0)25 (35.7) 
Hispanic ethnicity
Yes6 (13.6)3 (14.3)9 (12.7)0.944
No38 (86.4)18 (85.7)56 (78.9) 
Hepatitis B37 (77.1)21 (91.3)58 (81.7)0.199
Hepatitis C11 (22.9)2 (8.7)13 (18.3) 

All of the 48 enrolled case patients reported symptoms of acute hepatitis with discrete onset of symptoms, consistent with requirements of the surveillance case definitions. From onset of symptoms to study enrollment and interview, the median interval was 10 weeks. Jaundice was reported by 67% of case patients. Symptoms of acute hepatitis were listed as a primary indication for viral hepatitis diagnostic testing by 79% of the case patients. Insurance status among cases and controls was similar, with 2% of cases and 3% of controls reporting that they were uninsured; similar percentages of cases (56%) and controls (55%) reported Medicaid or Medicare coverage. Difficulty going outside the home alone to shop or visit a doctor's office was reported by similar percentages of cases (8%) and controls (11%).

Demographic characteristics of the hepatitis B and hepatitis C cases were similar (data not shown). Sixty-seven percent (32 of 48) of the cases occurred among males, whereas 61% (97 of 159) of controls were females (Table 2). Therefore, all multivariate models included sex (i.e., gender) to adjust for this difference. Of note, the overrepresentation of men among cases in this study was consistent with the distribution overall for acute hepatitis B (male-to-female ratio of 1.6:1 during 2007) and acute hepatitis C (1.2:1 male-to-female ratio in 2007).7 The proportion of females among control subjects (61%) was comparable to the proportion of females among the U.S. population ≥55 years (56%).18

Table 2. Descriptive Statistics and Univariate Matched Analysis of Demographic Characteristics and Behavioral and Healthcare Exposures Among Cases of Acute Hepatitis B and Acute Hepatitis B and Their Matched Controls
CharacterisiticCasesControlsP-valueMatched Odds Ratio (95% Confidence Interval)
  • *

    New York State Department of Health enhanced viral hepatitis surveillance program included 57 counties, outside of the 5 counties that comprise New York City.

  • 8 hepatitis B and 2 hepatitis C case-patients reported at least one behavioral risk exposure.

  • Includes laparoscopic and arthroscopic procedures, biopsies, cardiac catheterizations, cataract or other eye surgeries, and all other inpatient or outpatient surgical procedures.

  • §

    Includes all therapeutic injections and infusions, including allergy or pain medications, anesthesia, chemotherapy, imaging dye, steroids or vitamins, and excluding vaccinations.

  • Includes colonoscopy, sigmoidoscopy, cystoscopy, uteroscopy, and any other endoscopic procedures.

Age category (years)    
 55-5910 (20.8)29 (18.2)N/AN/A
 60-6925 (52.1)80 (50.3)  
 70+13 (27.1)50 (31.5)  
 New York (state)*21 (43.8)62 (39.0)N/AN/A
 New York City18 (37.5)70 (44.0)  
 Oregon9 (18.8)27 (17.0)  
 Female16 (33.3)97 (61.0)0.0010.36 (0.18, 0.69)
 Male32 (66.7)62 (39.0)  
 White33 (78.6)123 (79.9)0.4390.60 (0.60, 2.20)
 Other9 (21.4)31 (20.1)  
Hispanic ethnicity6 (12.5)9 (5.7)0.0785.47 (0.77, 38.85)
Work setting with blood/body fluid contact3 (6.4)6 (3.8)0.4291.74 (0.42, 7.23)
Traveled outside United States/Canada4 (8.5)11 (6.9)0.7511.25 (0.38, 4.13)
Behavioral risk exposure    
- Contact with infected person4 (9.1)4 (2.5)0.0693.87 (0.93, 16.17)
- More than one sex partner3 (6.4)2 (1.3)0.03410.25 (0.91, 115.57)
- Used street drugs2 (4.2)1 (0.6)0.1356.87 (0.61, 77.47)
- Incarcerated2 (4.2)0 (0)0.052
- Any of the above10 (20.8)7 (4.4)0.0017.07 (2.08, 24.06)
Dental procedure10 (20.8)71 (44.7)0.0010.25 (0.10, 0.61)
Podiatry care8 (16.7)33 (20.8)0.80.90 (0.38, 2.10)
Hospital emergency room visit12 (25.0)19 (12.0)0.0182.61 (1.12, 6.09)
Surgical procedure16 (33.3)29 (18.2)0.0172.31 (1.14, 4.67)
Injection§28 (58.3)58 (36.5)0.0062.65 (1.32, 5.32)
Hospitalization requiring overnight stay13 (27.1)13 (8.2)<0.0014.26 (1.75, 10.34)
Skin care procedure4 (8.3)23 (14.5)0.290.55 (0.17, 1.72)
Transfusion of blood products8 (16.7)3 (1.9)<0.00123.43 (2.73, 201.21)
Any endoscopy procedure8 (16.7)24 (15.1)0.8951.06 (0.44, 2.58)
Hemodialysis4 (8.3)1 (0.6)0.00113.03 (1.48, 114.59)

No case patients reported receiving a tattoo or piercing, employment in a medical or dental field, or having sustained a healthcare-related sharps injury in the 6 months before disease onset. Hepatitis B vaccination was reported by 4 of 48 (8%) case patients; 3 reported receiving only one or two doses (whereas the complete hepatitis B vaccination series consists of three doses), and the fourth was a dialysis patient. No case patients reported injection drug use. Homosexual behavior was not reported among enrolled male cases (information was incomplete for 1 case). Four case patients, 2 with hepatitis B and 2 with hepatitis C, reported having had contact with an infected person during their potential exposure periods. Though uncommon, other behavioral risks (e.g., sex with more than one person or use of street drugs) were more frequently reported among cases than controls (Table 2). The composite behavioral risk variable, which included sexual or household contact with a person having HBV or HCV infection, multiple sex partners, use of noninjecting street drugs, or having been incarcerated, was significantly associated with case status in univariate analysis (21% of cases versus 4% of controls exposed; P = 0.01).

Receipt of healthcare for any reason during the exposure period was reported by 94% of case patients and 89% of controls. Several healthcare exposures were associated with case status in the univariate analysis, including hospital emergency department visits, surgical procedures, parenteral injections, overnight hospitalizations, blood transfusions, and hemodialysis. Distribution of healthcare exposures among hepatitis B and hepatitis C cases was comparable (data not shown); for example, injections were reported by 57% of case patients with hepatitis B and 64% of those with hepatitis C. Controlling for study subjects' sex (i.e., gender) in the multivariate analysis, we found that reporting a behavioral risk exposure, having had injections in a healthcare setting, and having undergone hemodialysis were associated with acute hepatitis B or C infection (Table 3). Population-attributable risks associated with injections or hemodialysis were 37% and 8%, respectively. Overall results were similar in the multivariate model that used data incorporated from medical chart reviews (Supporting Information Table S1). Likewise, results were similar in a multivariate model that excluded hepatitis C cases and included only the 37 acute hepatitis B cases and their matched controls (Supporting Information Table S2).

Table 3. Matched Multivariate Analysis of Variables Associated With Acute Hepatitis B or Acute Hepatitis C Among Adults 55 Years or Older
  CaseControlAdjusted Odds Ratio (95% Confidence Interval)Population Attributable Risk (%)
Variable Frequency (%)Frequency (%)
  • 1

    Includes subjects reporting contact with an infected person, sex with more than one partner, the use of street drugs, or incarceration.

  • 2

    Includes all therapeutic injections and infusions, including allergy or pain medications, anesthesia, chemotherapy, imaging dye, steroids or vitamins, and excluding vaccinations.

SexFemale16 (33.3)97 (61.0)  
Male32 (66.7)62 (39.0)2.60 (1.25, 5.42)N/A
Behavioral risk exposure1Yes10 (20.8)7 (4.4)  
No38 (79.2)152 (95.6)5.36 (1.52, 18.98)16.9
Injection2Yes28 (58.3)58 (36.5)  
 No20 (41.7)101 (63.5)2.72 (1.26, 5.84)36.9
HemodialysisYes4 (8.3)1 (0.6)  
 No44 (91.7)158 (99.4)11.48 (1.23, 106.80)7.6


The results of this study suggest that healthcare-related exposures may contribute to HBV and HCV transmission to a greater extent than was previously recognized. Our results indicated that injections of parenteral medications could account for most of this risk. We showed that among persons 55 years or older, the proportion of new infections likely attributable to injections (excluding vaccinations) was 37%. Furthermore, approximately 8% of cases could be attributed to hemodialysis. These findings, along with increasing recognition of outbreaks of healthcare-associated viral hepatitis, are a sobering reminder that basic patient safety, in the form of bloodborne pathogen protections, cannot be taken for granted.

Although our study included only persons 55 years or greater, unsafe healthcare has the potential to affect patients of any age, as demonstrated in recent U.S. outbreak investigations.19-22 Of note, among hepatitis B and C cases with interview information available, between approximately one third and two thirds have unknown or unidentified risks.4, 7, 11 Unrecognized medical transmission could account for some of these cases. Our findings underscore the need for further study of sporadic healthcare-associated viral hepatitis transmission and for improved hepatitis surveillance capacity at state and local health departments.3, 5, 6 Questions regarding receipt of injections and infusions, as well as dialysis, hospitalizations, surgery, and long-term care residency, are included on the standard CDC case interview forms;23 health departments should be mindful of the need to enquire specifically about these exposures when interviewing persons with acute hepatitis B and C.

Risks for viral hepatitis transmission in healthcare settings may have increased over the past decade or so, although the published literature on acquisition of acute viral hepatitis in U.S. healthcare settings outside of outbreak reports has been sparse.9, 24, 25 Possible reasons include the shift in healthcare delivery to ambulatory care settings, where the volume and complexity of care are increasing and utilization is highest among older adults.13, 26 Compared to hospitals, emphasis on infection control in ambulatory and long-term care settings has been lacking and these facilities often operate with little oversight from licensing boards and state or federal authorities.9, 10, 21, 27 Though the risks of healthcare-associated HCV infection are difficult to quantify, the reservoir of potential source patients is likely increasing. For example, the prevalence of HCV infection is highest among persons born between 1945 and 1964.2 Members of this cohort will progressively come into more contact with the healthcare system as a natural consequence of aging as well as to receive specific HCV-associated care.28 Thus, there is a growing reservoir of infected individuals who can serve as a source of transmission to others if safe injection practices and other basic infection control precautions are not followed.

The potential for bloodborne pathogen transmission should be recognized whenever an invasive healthcare procedure is performed. During administration of injections and infusions, syringes and related equipment routinely become contaminated with microscopic quantities of blood.12 If syringes are reused to administer medication to more than one patient or to access shared medication, transmission of bloodborne pathogens can occur. This has been demonstrated repeatedly in recent outbreaks caused by syringe reuse and other unsafe injection practices,10, 12, 19-22 as well as in decades-old experimental studies.12 There is also growing recognition of provider-to-patient HCV transmission in the context of narcotics theft.29 Though rarely recognized, outbreaks involving infected healthcare providers who obtained injectable drugs illicitly have affected large numbers of patients.29 Safe injection practices include one-time use of syringes, needles, and single-dose vials.12, 30-32 True multidose vials should be dedicated for single patient use whenever possible; when shared use is unavoidable, these should be handled in an aseptic manner away from potentially contaminated patient treatment areas.12, 30-32 These recommendations are part of accepted evidence-based guidelines for preventing healthcare-associated infections, but ongoing outbreaks and gaps in adherence27, 31 indicate that these need to be reinforced as part of medical and nursing school curricula, other preservice healthcare training, and mandated, routine continuing education activities.5, 12, 22, 33-35 Likewise, efforts toward enforcement of basic standards of infection control and effective oversight activities (e.g., audits and inspections), though increasing, require strengthening at both the state and federal levels.5, 12, 21, 27 In addition, there is a critical need for broader application of safety-engineered technologies, systems, and strategies (e.g., commercial prefilled syringes utilizing tamper-proof packaging) to prevent reuse of injection equipment and limit sharing of parenteral medications.5, 35, 36

Hemodialysis, another important risk identified in our study, involves repeated, prolonged access to patient's bloodstreams and poses long-recognized risks for bloodborne pathogen transmission.12, 37, 38 Specific infection control and hepatitis B vaccination recommendations that apply to patients undergoing care in hemodialysis settings have reduced these risks, but are often overlooked, as evidenced from ongoing outbreaks and the findings presented here.37-41 Similarly, fundamental infection control errors related to assisted monitoring of blood glucose have been clearly associated with numerous HBV infection outbreaks in long-term care settings.12, 42-44 Again, these point to the need for oversight and enforcement of basic infection control standards.

Our study was limited to incident, symptomatic cases. This approach permits an evaluation of exposures within a defined period before symptom onset. However, it also meant that we were limited by the number of incident cases meeting our inclusion criteria. Cases occurring among nursing home residents or identified as part of outbreak investigations were excluded from this study. In fact, two outbreaks were documented in connection with our study, one in relation to an excluded hepatitis B case patient who resided in a long-term care facility where unsafe blood-glucose monitoring practices resulted in transmission of HBV infection to at least 6 residents.45 The other outbreak involved one of the enrolled hepatitis C cases, who served as the index case for an outbreak investigation that eventually identified 6 acute hepatitis B cases and 5 additional acute hepatitis C cases (none of which were included in our case-control study).20 In the end, our small sample size resulted in limited statistical power, with wide confidence intervals around some of the adjusted odds ratios, especially for low-frequency exposures. This also prevented us from examining hepatitis C as an outcome separate from hepatitis B.

The findings in this report were subject to several other limitations. The proportions of men and women in the case and control groups differed significantly. This imbalance reflects known differences among incident hepatitis B and C cases and population structure at national levels,7, 18 and we adjusted for sex (i.e., gender) in our risk factor and attributable risk analyses. The higher incidence of HBV and HCV infections among men is thought to reflect higher prevalences of behavioral risk factors relative to women. Though our study did identify behavioral exposures as contributing to acquisition of infection in our study population, it is possible that this contribution was underestimated. Reluctance to disclose behavioral risks (e.g., illicit drug use or homosexual behavior and other sexual exposures) is well described and was one motivation for our use of a composite variable that included a broader array of exposures. For example, incarceration and general illicit drug use are not direct risk factors for acute hepatitis B or C, but might serve as surrogate indicators for such factors. Nonetheless, underascertainment of behavioral risk factors may explain the large percentage of cases (approximately 40%) that did not have a defined risk factor. Other limitations pertain to potential recall bias and incomplete medical record reviews. A large percentage of control subjects declined to authorize access to their medical charts and it was not possible to gain access to all relevant records in some instances. To reduce errors associated with recall, study participants were encouraged to consult a calendar and personal records during interviews. We found that chart review tended to increase the ascertainment of individual exposures, but this effect was modest (e.g., for the injection variable, information from chart reviews increased the total number of exposed study participants from 86 to 93). The model results using interview findings alone or supplemented by chart reviews were also shown to be generally concordant. Finally, the limited number of study sites and focus on older adults mean that our results are not generalizable to the overall U.S. population. On the other hand, our study used population-based surveillance and included a diverse mix of urban/rural and geographically disparate study sites.

In summary, our case-control study demonstrated that healthcare exposures may represent an important source of HBV and HCV infection among older adults and suggests that healthcare transmission is not limited to recognized outbreaks. These findings point to the need for renewed commitment to improved public health surveillance for viral hepatitis and stronger oversight of basic infection control procedures in all healthcare facilities.3, 5, 10, 12, 33-35 To prevent the spread of viral hepatitis, it is important that healthcare providers take responsibility for assuring that safe practices are understood and followed by all.


The authors gratefully acknowledge the assistance and guidance provided by Magdalena Berger, Ian Willams, Kathy Gallagher, and Beth Bell.