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| Year : 2005 | Volume
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| Issue : 1 | Page : 186-192 |
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| The epidemiology of hepatitis B virus infection in healthcare workers in the West and Asia |
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Miriam J Alter
Division of Viral Hepatitis, Mailstop D66, Centers for Disease Control and Prevention, 1600, Clifton Road, Atlanta, Georgia 30333, USA
Click here for correspondence address and email
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How to cite this article:
Alter MJ. The epidemiology of hepatitis B virus infection in healthcare workers in the West and Asia. Hep B Annual 2005;2:186-92 |
Hepatitis B virus (HBV) infection is a well-recognized occupational risk for healthcare workers.[1] The risk of infection has been demonstrated to be primarily related to the degree of contact with blood in the work place.[2],[3] Serologic studies conducted in low HBV prevalence countries during the 1970s demonstrated that healthcare workers had a prevalence of HBV infection up to 10 times higher compared to the general population[4] Because of the high risk of HBV infection among healthcare workers, routine preexposure vaccination of healthcare workers against hepatitis B and the use of universal precautions to prevent exposure to blood and other potentially infectious body fluids have been recommended in many countries since the vaccine became available in the early 1980s. In the United States, regulations issued by the Occupational Health and Safety Administration have increased compliance with these recommendations.[4],[5]
The principle modes of HBV transmission in the healthcare setting are 1) direct percutaneous inoculation of blood or body fluids containing HBV via needle-stick or other injuries from sharp instruments, 2) direct inoculation of blood or body fluids containing HBV on to mucous membranes, cutaneous scratches, abrasions, burns or other lesions, and 3) indirect inoculation of HBV from environmental surfaces contaminated with blood or body fluids on to mucous membranes, cutaneous scratches, abrasions, burns or other lesions. Blood contains the highest HBV titers and is the most important vehicle of transmission in the healthcare setting. HBV is relatively stable in the environment and remains viable for at least 7 days on environmental surfaces at room temperature.[6] Although hepatitis B surface antigen (HBsAg) has been detected in a wide variety of other body fluids including breast milk, bile, cerebrospinal fluid, feces, naso-pharyngeal washings, saliva, semen, sweat, and synovial fluid, the concentration of HBsAg in body fluids can be 100 to 1000-fold higher than the concentration of infectious HBV particles. Therefore, most body fluids are not efficient vehicles of transmission because they contain low quantities of infectious HBV, despite the presence of HBsAg.
Patient to healthcare worker transmission of HBV infection
Injuries from needles contaminated with HBV infected blood are one of the most efficient means of HBV transmission in the healthcare setting. The average volume of blood inoculated during a needle-stick injury with a 22 gauge needle is approximately 1 Fl,[7] a quantity sufficient to contain up to 100 infectious doses of HBV.[8] In studies of healthcare workers who sustained injuries from needle-sticks contaminated with blood from HBsAg-positive persons, 6% to 14% developed clinical hepatitis B and 27% to 45% developed serologic evidence of HBV infection.[1] The risk of developing clinical hepatitis from a needle contaminated with hepatitis B e antigen (HBeAg)-positive blood was 22% to 31%, and the risk of serologic evidence of HBV infection was 37% to 62%. By comparison, the risk of developing clinical hepatitis from a needle contaminated with HBeAg-negative blood was 1% to 6%, and the risk of serologic evidence of HBV infection was 23% to 37%.
Although overt percutaneous injuries are one of the most efficient modes of HBV transmission, these exposures probably account for only a minority of HBV infections among healthcare workers. In several investigations of nosocomial hepatitis B outbreaks, most infected healthcare workers could not recall an overt percutaneous injury.[9],[10] Similarly, in case series of healthcare workers with acute hepatitis B, only a small proportion (<10%) recalled a specific percutaneous injury; however, up to one third recalled caring for a HBsAg-positive patient within 6 months prior to onset of illness.[11] Direct blood or body fluid exposures that may result in HBV infections can include inoculation of HBV into cutaneous scratches, abrasions, burns, or other lesions, or inoculation of HBV on to mucosal surfaces such as by mouth pipetting or accidental splashes in the eyes.
Multiple factors influence the risk of HBV infection among healthcare workers, including the prevalence of HBsAg-positivity in the general and patient populations, the prevalence of immunity to HBV due to natural infection or immunization among healthcare workers, and the frequency with which HBsAg-positive exposures occur in the occupational setting. The relative contribution of these factors to HBV infection in healthcare workers differs between Asian and Western countries.[12],[13],[14],[15] In Asian countries, there is a high level of natural immunity to HBV infection (and fewer adults are vaccinated), but there is also a higher prevalence of chronic HBV infection in the population, a higher rate of occupational injuries or exposures, and thus, a higher risk of HBsAg-positive exposures. In contrast, in Western countries, most immunity to HBV infection is the result of immunization, the prevalence of chronic HBV infection in the general population is low, and the rate of occupational injuries or exposures has diminished substantially during the past 15 years.
Healthcare worker to patient transmission of HBV
The vast majority of healthcare personnel infected with a bloodborne virus do not pose a risk to patients, because they do not perform activities where the conditions necessary for transmission are met.[16] Three conditions are necessary for healthcare personnel to pose a risk for bloodborne virus transmission to patients. First, the healthcare provider must be viremic (i.e., have infectious virus circulating in the bloodstream). Second, the healthcare provider must be injured or have a condition (e.g., weeping dermatitis) that allows direct exposure to his/her blood or other infectious body fluids. Third, the provider's blood or infectious body fluid must gain direct access to a patient's wound, traumatized tissue, mucous membranes, or similar portal of entry. Although an infected healthcare provider might be viremic, unless the second and third conditions are both met, transmission cannot occur. Specific factors influencing the transmission of HBV to patients have included the presence of high levels of virus and the performance of exposure prone invasive procedures or presence of other conditions allowing access to the worker's blood.
Most of the reported cases of HBV transmission worldwide occurred prior to 1991, before hepatitis B vaccination was widely used and before standard (universal) infection control precautions were implemented; most of these involved infected surgeons, oral surgeons or dentists.[12],[16] Other healthcare providers implicated in HBV transmission to patients included a respiratory therapist, cardiac pump technicians, an electroencephalography technician and a general practitioner. Unlike the transmissions involving invasive procedures performed by surgeons and dentists, skin conditions in these healthcare providers (e.g., exudative dermatitis, bleeding lesions or cuts) and poor technique contributed to transmission. Since 1991, the number of reported episodes of HBV transmission to patients from infected surgeons has declined by 67%; these more recent episodes involved healthcare providers who were negative for HBeAg. These providers were infected with HBV strains that had mutations in the precore region of the viral genome that prevents expression of HBeAg.
Prevention of HBV infection
Any healthcare worker who performs tasks involving contact with blood, blood-contaminated body fluids, other body fluids, or sharps should be vaccinated or have serologic evidence of immunity due to natural infection.[12] Hepatitis B vaccine should always be administered by the intramuscular route in the deltoid muscle with a needle 1-1.5 inches long. Healthcare workers who have contact with patients or blood and are at ongoing risk for injuries with sharp instruments or needlesticks should be tested 1-2 months after completion of the 3 dose vaccination series for antibody to hepatitis B surface antigen (anti-HBs). Persons who do not respond to the primary vaccine series should complete a second 3-dose vaccine series or be evaluated to determine if they are HBsAg-positive. Revaccinated persons should be retested at the completion of the second vaccine series.
Because recommendations for hepatitis B vaccination in healthcare settings, including pre- and post-vaccination testing may differ by country, the specific policy of the country should be consulted. Similarly, recommendations regarding limitations or restrictions of HBsAg-positive healthcare workers differ by country, and involved countries with no policy, countries in which the policy is to review the practices of HBeAg-positive workers who perform exposure prone invasive procedures, and countries in which those with serum HBV DNA above a certain level are restricted from performing such procedures.[12] As with vaccination policies, the specific policy of the country for HBV-infected healthcare workers should be consulted.
Preventing the transmission of bloodborne pathogens, including HBV, from patients to healthcare workers and from healthcare workers to patients requires a comprehensive approach that includes administering hepatitis B vaccine to all susceptible healthcare workers at risk, viewing all blood as potentially infectious, using measures to reduce blood exposures, and having a staff committed to safe work practices.[17] Critical elements to this approach include adherence to standard (universal) precautions, appropriate cleaning and disinfection procedures, safe injection practices, and reducing the risks for injuries (e.g., use of blunted suture needles, needleless intravenous set-ups, etc.).
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Correspondence Address:
Miriam J Alter
Division of Viral Hepatitis, Mailstop D66, Centers for Disease Control and Prevention, 1600, Clifton Road, Atlanta, Georgia 30333
USA
 Source of Support: None, Conflict of Interest: None  | Check |
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