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Bloodborne Pathogen An Overview
HIV is the virus that causes AIDS. Once infected with HIV, a person may
live for years before developing AIDS. Because HIV gradually weakens the immune system, it
eventually lowers the body's resistance to many kinds of illnesses. Individuals infected
with HIV are considered to have AIDS when severe immunosuppression develops.
Why haven't more people been infected with HIV?
- HIV is predominantly transmitted by three major routes: sexual contact,
exposure to infected blood or blood components, or perinatally from mother to child. In
the United States, most cases result from sexual contact. Although HIV can be cultured
from residual blood in needles for up to 24 hours, transmission of the virus has not been
documented to occur through casual contact or contact with environmental surfaces such as
furniture or bathroom facilities.
Common chemical germicides rapidly inactivate HIV. Even when percutaneous needle sticks
with HIV-infected blood occur, transmission of HIV results only approximately 0.3% of the
time (Table 1). For the individual, however, the actual transmission rate greatly depends
on the type of percutaneous exposure; very high-risk exposures are associated with a risk
of transmission much greater than 0.3%. Only a few isolated cases of infection after
exposure of mucous membranes or non-intact skin to HIV-infected blood have been reported,
making the odds of transmission through those routes significantly lower than the odds of
transmission following percutaneous exposure.
What are universal precautions?
- Universal precautions consist of several widespread recommendations made
by the CDC and mandated by the Occupational Safety and Health Administration (OSHA) to
lower the risk of occupational HIV transmission. Before universal precautions were
recommended, blood and body fluid precautions were reserved for patients at high risk of
being infected with blood-borne pathogens such as HBV. In other words, health care workers
were advised to wear gloves, put on gowns, and take other precautions to avoid contact
with the blood and body fluids of potentially infected patients. However, many patients
with infectious diseases cannot be readily identified by health care workers either
because these patients are in the asymptomatic incubation period or because they remain
infectious after symptoms have resolved. These and other considerations led experts to
conclude that blood and body fluid precautions should be used for all patients whenever a
health care worker can reasonably predict or anticipate contact with blood or other
potentially infectious materials.
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- With the advent of the HIV epidemic, the CDC now recommends that health
care workers consider all patients potentially infected with HIV or other blood-borne
infections. Therefore, health care workers should take precautions to avoid the blood and
body fluids of all patients. OSHA has issued a final rule, known as the Blood-Borne
Pathogen Standard (29 CFR 1910.1030), that requires employers to provide employees with a
training program on safe work practices and personal protective equipment when
occupational exposure to blood or other potentially infectious materials is reasonably
anticipated.
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- To assist hospitals in maintaining up-to-date isolation practices, the
CDC and the Hospital Infection Control Practices Advisory Committee (HICPAC) have revised
the "CDC Guidelines for Isolation Precautions in Hospitals." These guidelines
help clarify the interpretation of universal precautions and incorporate precautions to
prevent airborne disease transmission. CDC recommendations are not legally binding, as is
the OSHA standard.
Which body fluids contain HIV and which of them can transmit the disease?
- HIV has been isolated from blood, semen, vaginal secretions, saliva,
tears, breast milk, cerebrospinal fluid, amniotic fluid, and urine, and it is probably
present in other body fluids. However, only blood, semen, vaginal secretions, and breast
milk have been implicated in transmission. Nevertheless, all body fluids should be treated
as potentially infectious.
Do I have to follow universal precautions for all body fluids?
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Universal precautions apply to the following:
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Blood |
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Body fluids containing visible blood |
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Body fluids in which it is difficult or impossible to distinguish individual body fluids |
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Semen |
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Vaginal secretions |
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Any unfixed human tissue or organ |
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Cerebrospinal fluid |
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Synovial fluid |
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Pleural fluid |
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Peritoneal fluid |
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Pericardial fluid |
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Amniotic fluid |
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Saliva |
- OSHA has further clarified that "blood" includes human blood,
human blood components, and products made from human blood. OSHA does not make an
exception for albumin human USP even though it is sterile. Universal precautions also
apply to any unfixed tissue or organ (other than intact skin) from a human or a human
corpse.
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- Studies both in the community and in health care facilities have
demonstrated that the risk of HIV transmission from other excretions, such as feces, nasal
secretions, sputum, sweat, tears, urine, and vomitus is extremely low or nonexistent -- as
long as they do not contain blood. Because these excretions may harbor other infectious
agents such as HBV and cytomegalovirus, health care workers should implement body fluid
precautions when exposure is anticipated.
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- Although breast milk has been implicated in perinatal transmission of
HIV, it does not appear to pose an occupational danger. If workers have contact with
breast milk, such as in milk banking, they should wear gloves
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Should I wash the wound with disinfectant, bleach, or some other
cleansing agent?
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There is no evidence that washing with antiseptics, bleach, or other
chemicals is more effective in preventing infection than washing with soap and water.
Aspiration, forced bleeding, and wound incision are also not recommended.
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What should I do if the person's blood or body fluid splashes in my
eyes?
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Ideally, use a sterile saline or sterile commercial eyewash to
thoroughly flush your eyes. If those are not available, use clean running water.
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What should I do if the person's blood or body fluid comes in
contact with my nose or mouth?
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Thoroughly flush the mucous membranes in the nose and mouth with clean
running water or a saline solution.
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What should I do if the person's blood or body fluid comes in contact with an open
sore on my skin?
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Wash the area thoroughly with soap and water.
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What should I do if the person's blood or body fluid splashes my
skin?
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If you do not have any lesions where the fluid splashed, it is not
considered to be an "exposure incident." Simply wash the area with soap and
water. Such exposures should not pose a danger of transmission, and it is not necessary to
report these.
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Is it necessary to report the exposure? If so, to whom?
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If you have any contact with a person's blood or body fluids (except
blood or body fluid splashes on intact skin), you should immediately report it to your
facility's employee health service, emergency room, or designated infection-control
professional. This step is critical because it provides an opportunity to discuss HBV or
HIV prophylaxis and it also helps document an occupational injury if disputes arise later
over payment of medical bills or lost wages. Your report should include the following
information
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date and time of exposure; |
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job duty or procedure being performed at the time of the incident; |
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detailed description of the incident, including specific information such as which
safety devices were being used, the amount and type of fluid, method of exposure, and
extent and duration of contact; |
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source of exposure and the source patient's HIV, HBV, and HCV status if known; and |
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decontamination procedures used. |
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Your hospital or a designated resource should provide you with testing,
counseling, treatment, and follow-up in accordance with the OSHA standard. Occupational exposure to HIV can be a very frightening experience. It is
vital that you report the exposure not only to receive medical attention and evaluation,
but also to receive support and counseling to help you deal with the possible
psychological stress. HIV testing should never be performed without appropriate
counseling.
Are all exposures equally risky, or are some types of exposures more
dangerous than others?
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Although data remain inconclusive, many factors probably affect the risk
of occupational transmission. For the injury itself, the following factors may influence
the risk: (1) the type of exposure (percutaneous, mucosal, or cutaneous); (2) the fluid
involved (blood or other body fluids); (3) the concentration of HIV in the fluid; (4) the
depth and duration of exposure; (5) physical factors (temperature, pH, humidity); and (6)
the age of the specimen. In general, injection of large quantities of blood and deep
inoculations pose the highest risk. The source's stage of disease and type of treatment
may affect the amount of HIV present in the blood or tissue. Most occupational
transmissions have occurred after exposure to patients with late-stage AIDS; however, such
patients are more often hospitalized and require medical interventions involving sharp
objects than those without late-stage AIDS.
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In a recently published retrospective case-control study by the CDC that
involved health care workers who had documented occupational percutaneous exposure to
HIV-infected blood, four factors were independently associated with the transmission of
HIV from a source patient to a health care worker: (1) a deep percutaneous injury; (2)
visible blood on the device; (3) injury with a device that had been placed directly into a
vein or artery of the source patient; and (4) a source patient with a terminal illness
(presumably associated with a greater viral burden). These findings support an earlier
study that had identified the above-mentioned factors associated with occupational HIV
seroconversion.
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What is the risk of infection with HBV?
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The risk of transmission after percutaneous exposure to blood infected
with HBV is approximately 30%.
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What is the risk of infection with HCV?
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With the recent development of an accurate assay to detect antibody to
hepatitis C, researchers have begun to explore the risk of HCV transmission to health care
workers. Seroprevalence of the virus among hospitalized patients can be quite high -- as
high as 18% in one study. Early studies, however, indicate a relatively low rate of
transmission per exposure. In one study, seroconversion occurred in only 4% of 110
hospital employees who had percutaneous exposures involving the blood of anti-HCV-positive
patients. At The Johns Hopkins Hospital, only 0.7% of health care workers had antibodies
to HCV, whereas 6.2% had antibodies to HBV core antigen. Nevertheless, if HCV infection
does occur, it frequently causes severe chronic hepatitis. Because no HCV vaccine is
currently available and the efficacy of prophylactic gamma globulin in preventing
transmission of HCV remains uncertain, no specific therapy is currently recommended for
health care workers exposed to HCV other than standard procedures for immediate
decontamination.
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Will treatment be necessary if I have been vaccinated for HBV?
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If the source patient is positive for the hepatitis B surface antigen
(HBsAg), you should also be tested for antibody to HBsAg -- even if you have received the
vaccine. If your antibody level is not adequate, you should receive one dose of hepatitis
B immune globulin (HBIG) and one dose of vaccine. If the source patient is unknown or
refuses testing, decisions to test or treat vaccinated workers should be determined on an
individual basis.
Are the HBV vaccine and HBIG safe?
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HBV vaccine may be manufactured from either human plasma or by
recombinant DNA technology. The plasma version is no longer manufactured in the United
States, so all recombinant vaccines are produced by using hepatitis B antigen synthesized
by common baker's yeast. Although a possible association between Guillain-Barré syndrome
and the first dose of a plasma-derived vaccine was reported in the United States,
available data from surveillance of 2.5 million adults receiving one or more doses of
recombinant vaccine between 1986 and 1990 do not indicate an association with the disease.
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HBIG is prepared from human plasma with a high titer of antibody against
HBsAg. The plasma is screened for antibodies to HIV. In addition, HIV is inactivated and
eliminated from the final product by the process used to prepare the vaccine. There is no
evidence that HIV transmission has ever occurred via HBIG.
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What treatment is necessary if I have never received the vaccine?
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If you have never received the HBV vaccine and are not immune from prior
infection, you should receive the series now, regardless of whether the source patient is
positive or negative for HBsAg. If the source patient is positive, you should also receive
one dose of HBIG, provided it can be given within 7 days of the exposure. If the source
patient is unknown or refuses testing, you should still receive the vaccine series, but
decisions regarding HBIG should be made on an individual basis, The OSHA standard
requires the employer to make the HBV vaccine available to all employees at risk for
occupational exposure and to provide postexposure evaluation and follow-up to all
employees who have had an exposure incident.
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Does being HIV-positive automatically mean I will develop AIDS?
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The World Health Organization AIDS projection model predicts that
approximately 75% of HIV-infected individuals will develop AIDS within 15 years of their
initial infection. The mean latency period for AIDS is about 7-10 years. This period,
however, can vary from less than 1 year to more than 10 years. Some individuals show
evidence of HIV infection but no evidence that their immune system has weakened, even
after 15 years or more of HIV infection. In addition, for those persons who receive the
newer, more effective antiretroviral combination regimens, preliminary evidence suggests
that their progression to AIDS will be markedly delayed.
Is HIV infection permanent? That is, does the risk of AIDS continue
indefinitely?
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HIV infection does appear to be permanent. Even those individuals who
have not shown evidence of progressive immunosuppression still test positive for HIV
infection and can still transmit the virus.
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Specifically, AIDS refers to either laboratory evidence of severe
immunosuppression (CD4 count less than 200 cells/mm3) or clinical evidence of
severe immunosuppression (opportunistic infections and malignancies)
Fig 1. -- AIDS annual rates per 100,000 population, for cases
reported July 1995 through June 1996, United States.
Adapted from the Centers for Disease Control and
Prevention.
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