Bloodborne Pathogens
Bloodborne Pathogens
History and Scientific Foundations
Introduction
Bloodborne pathogens are microscopic disease-causing organisms that are present in the blood of humans with certain infections that can cause disease in other humans who come in contact with the infected blood. The three major bloodborne pathogens are: hepatitis B virus (HBV), hepatitis C virus (HCV), and the human immunodeficiency virus (HIV), although other diseases can be transmitted via the bloodborne route of infection. Exposure to blood containing any of these pathogens carries a risk of transmission of the infection.
Healthcare workers, including doctors, dentists, and nurses, can become exposed through needlestick injuries, which occur if they are accidentally pricked with a needle that has been used on an infected person. Drug users who share needles can also become infected with bloodborne pathogens, and this is a major route of transmitting HCV. In the past, people receiving blood transfusions and blood products were also at risk of infection by bloodborne pathogens. Reducing the risk from bloodborne pathogens depends upon people following the strict precautions laid down by the Occupational Safety & Health Administration (OSHA) in the United States and equivalent organizations in other countries.
WORDS TO KNOW
BLOODBORNE ROUTE: Via the blood. For example: Bloodborne pathogens are pathogens (diseasecausing agents) carried or transported in the blood. Bloodborne infections are those in which the infectious agent is transmitted from one person to another via contaminated blood. Infections of the blood can occur as a result of the spread of an ongoing infection caused by bacteria such as Yersinia pestis, Haemophilus influenzae, and Staphylococcus aureus.
NEEDLESTICK INJURY: Any accidental breakage or puncture of the skin by an unsterilized medical needle (syringe) is a needlestick injury. Healthcare providers are at particular risk for needlestick injuries (which may transmit disease) because of the large number of needles they handle.
PATHOGEN: A disease-causing agent, such as a bacteria, virus, fungus, etc.
POSTEXPOSURE PROPHYLAXIS: Postexposure prophylaxis is treatment with drugs immediately after exposure to an infectious microorganism. The aim of this approach is to prevent an infection from becoming established.
STANDARD PRECAUTIONS: Standard precautions are the safety measures taken to prevent the transmission of disease-causing bacteria. These include proper hand washing; wearing gloves, goggles, and other protective clothing; proper handling of needles; and sterilization of equipment.
History and Scientific Foundations
When HIV was identified in the early 1980s, it soon became clear that transmission through infected blood was a real possibility. Indeed, thousands of people with the blood clotting disorder hemophilia became infected with HIV because of their dependence on blood products. Now that blood and donors are screened in many countries—and there are efforts on the part of the World Health Organization (WHO) to make this a global practice—this route of exposure to HIV and the two other major bloodborne pathogens HBV and HCV has become less significant.
However, there is still a risk of transmission of bloodborne pathogens to those who become exposed to infected blood, either through their occupation or through their lifestyle. For healthcare workers, a major risk of exposure comes from needlestick injury (NSI), which occurs if a healthcare worker is pricked with a needle that has been used to in an injection or to take blood from an infected person. A NSI can occur either during the procedure itself, or during disposal of the needle. A similar risk exists from cuts occurring from sharp instruments, like scalpels, that have been contaminated with infected blood. Instruments that can cause this kind of injury are generally known as sharps. Splashes of infected blood to the eye, nose, mouth or skin also carry a risk. According to the National Institute for Occupational Safety and Health (NIOSH), there are between 600,000– 800,000 NSIs each year in the United States, with nurses being most at risk. And around one third of all NSIs take place during sharps disposal.
HBV is the most easily transmitted of the bloodborne pathogens. However, there is now a vaccine against HBV that is made available to those at risk. Without vaccination, there is a one-in-three chance of contracting HBV through a needlestick injury. For HCV, there is around a 2% risk of infection through NSI. The general risk of contracting HCV through exposure via a blood splash is not known, but there has been one case of infection through a splash in the eye and one from a splash into broken skin. Around 1% of healthcare workers have HCV infection, compared to around 3% of the general United States population. But it is not known how many of the healthcare worker HCV infections arose through occupational exposure.
For HIV, the risk of becoming infected through a needlestick injury is about one in three hundred, although the risk is higher when a person with advanced AIDS is the source of the infected blood. Deep injections, and instruments that are obviously contaminated with blood also carry a higher risk of infection. The risk following HIV-infected blood splashes is around one in a thousand. There have been no documented cases of HIV transmission due to an exposure involving contact of infected blood with intact skin.
Applications and Research
Commonsense precautions, such as protecting the hands, eyes, and mouth when dealing with blood from patients potentially infected with HBV, HCV, and HIV, can go a long way to reducing the risk of transmission of these bloodborne pathogens. It is also important to use properly trained staff (phlebotomists) to take blood samples. Simply reducing the number of times needles are used on patients, for injections, placing catheters, and taking blood samples, also reduces the risk of transmitting bloodborne pathogens, by cutting down on the number of occasions on which accidents can take place.
Science and technology have also contributed towards reducing the risk of transmission of bloodborne pathogens. For instance, the Centers for Disease Control and Prevention (CDC) say that the annual number of HBV infections has decreased more than 90% since the introduction of the vaccine in 1982. In 1983, there were more than 10,000 such infections in the United States every year and by 2001, this was down to fewer than 400. Unfortunately, there are no such vaccines against HCV or HIV, although research is ongoing. Postexposure prophylaxis (PEP) can be used to protect someone who may have been exposed to HIV through infected blood. This involves giving the antiretroviral drugs used to treat HIV/AIDS patients as soon as possible after exposure. Some studies have suggested this may reduce the risk of HIV transmission, although it is not universally recommended because the drugs have side effects and the risk of infection remains small.
Impacts and Issues
OSHA reports that 5.6 million workers in the United States are at risk of exposure to bloodborne pathogens. In 1991, OSHA issued the Bloodborne Pathogens Standard Prevention Act, which was updated in 2001. This law encompasses the “universal precautions” philosophy of CDC, now called standard precautions, and affects many aspects of the way healthcare, and other workers, carry out their day-to-day tasks. Basically, all persons receiving care are considered potentially contaminated with bloodborne pathogens unless proven otherwise, and therefore, using protective measures to avoid contact with blood is now standard procedure for healthcare workers.
Prevention of exposure involves physical protection of the worker with gloves, masks, and eye shields during surgery or other procedures where there is a potential for contact with blood. Safe devices such as retractable or sheathed needles must be used when taking blood, and any NSIs must be reported and followed up. Protection from infection depends upon all those who may be at risk taking this code seriously and following it before, during, and after handling blood from potential sources of bloodborne pathogen risk.
The advent of safer devices, such as needle-less injectors, has also been an important advance. CDC reports a 62–88% reduction in NSIs from the introduction of better devices. For injecting drug users at risk of bloodborne infections, especially HCV, education in harm reduction and needle exchange schemes may also reduce the incidence of new infections. However, it is difficult to document this, as there is often a lengthy time lag between exposure and evidence of infection.
See AlsoBlood Supply and Infectious Disease; Hepatitis B; Hepatitis C; HIV; Infection Control and Asepsis; Standard Precautions.
BIBLIOGRAPHY
Books
American Academy of Orthopedic Surgeons. Bloodborne Pathogens. 5th ed. New York: Jones and Bartlett, 2007.
Web Sites
Centers for Disease Control and Prevention (CDC). “Exposure to Blood: What Healthcare Personnel Need to Know.” July 2003 <http://www.cdc.gov/ncidod/dhqp/pdf/bbp/Exp_to_Blood.pdf> (accessed Feb 8, 2007).
Centers for Disease Control and Prevention (CDC). “Infection Control Guidelines.” <http://www.cdc.gov/ncidod/dhqp/guidelines.html> (accessed February 8, 2007).
U.S. Department of Labor Occupational Safety & Health Administration. “BloodbornePathogens and Needlestick Prevention OSHA Standards.” <http://www.osha.gov/SLTC/bloodbornepathogens.standards.html> (accessed February 8, 2007).
Susan Aldridge