Bloodborne Pathogens

Associated Risks

Nov 12, 2006

No doubt you are familiar with the term blood-borne pathogens, but do you understand what they are and the risks associated with becoming infected?

A blood-borne pathogen, as the term suggests, is a disease or infection-producing agent that can be acquired through exposure to blood and other body fluids containing blood. BBPs are transmitted from one individual to another when blood or body fluids from the infected individual enter the body of a previously uninfected individual.

Significant exposure involves a route of entry into the body:

sexual transmission through the mucous membranes of the genital tract,
splashes to the mucous membranes of the eyes (conjunctiva), nasal passages or mouth,
contamination or exposure of broken or damaged skin (broken, abraded, chapped, cuts, wounds, scratches, breaks around nail-beds, eczema, psoriasis, dermatitis, etc.)
percutaneous (across the skin barrier) transmission with a contaminated sharp (sharing of intravenous drug paraphernalia, sharps injury with a contaminated device)

There are a number of different infectious agents that can be transmitted through blood and body fluids containing blood including the human immunodeficiency virus (HIV), hepatitis B (HBV) and C (HCV) viruses, Treponema pallidum, malarial plasmodia, Trypanosoma cruzi and others. The three most common blood-borne infections in North America are HBV, followed by HCV, then HIV.

The specific body fluids capable of transmitting BBPs include:

blood, serum, plasma and all biologic fluids visibly contaminated with blood
tissues
pleural, amniotic, pericardial, peritoneal, synovial and cerebrospinal fluids (CSF)
cervical/vaginal secretions or semen (HCV)
saliva contamination in a bite wound

Infection occurs when the pathogen contained in the body fluid multiplies and causes disease. Exposure does not necessarily result in transmission, and transmission does not necessarily result in infection.

A number of factors affect the risk of transmission and infection following exposure:

Type of fluid exposure – blood poses a greater risk than saliva, for example
Volume of fluid – a hollow bore needle such as one that is used for venipuncture contains more blood on average than a suture needle or lancet
Probability of exposure – dependent on type of risk behaviour and work performed
Specific pathogen involved – on average, HBV infection is associated with greater numbers of viral particles in the patient’s blood and tissues at any one time than HCV or HIV
Route of exposure – percutaneous exposure results in greater risk of infection than exposure through mucous membranes or non-intact skin
Disease progression – viral particles may be found in much greater numbers in patients whose disease has progressed
Virus concentration in fluid or tissue (viral load)

Blood is the single most important source of HIV, HBV, and other BBPs in the occupational setting; therefore, transmission is most likely to occur in workers involved in rescue or patient care activities, or during other interactions where workers are directly exposed to infected blood. Occupational transmission of HIV, HBV and HCV in health care and public service settings is most commonly associated with injuries involving needles or other sharp instruments. Most HCW BBP exposures occur due to percutaneous sharps injury.

Health care workers (HCW) who handle blood and body fluids are at increased risk of infection with HBV, HCV and HIV – those most at risk include phlebotomists, nurses, clinical laboratory workers, and physicians. Exposure is most commonly associated with needle-stick injury or percutaneous injury resulting from other sharp instruments (i.e. lancets, scalpel blades, suture needles, broken glass, etc.). Other HCWs at risk are surgeons (scalpels and suture needles) and dental workers, as well as housekeepers and laundry workers who are exposed due to discarded or lost needles in waste and laundry.

The WHO reports that about 3 million of the 35 million health workers worldwide experience percutaneous exposures to blood-borne pathogens each

Year (2,000,000 to HBV, 900,000 to HCV and 170,000 to HIV). Of these injuries, approximately: 70,000 result in HBV infections, 15,000 HCV infections and 1,000 HIV infections. Greater than 90% of these infections occur in developing countries.

Emergency medical service and public-safety workers are also at risk of occupational exposure to BBPs. Emergency medical technicians (EMTs), fire fighters, law officers and prison guards may be exposed during the performance of their duties. In addition to exposure risk associated with responding to trauma scenes and sharps injuries, law officers and prison guards also risk bite wounds from suspects and prisoners. HBV infected saliva has been shown to contain much lower concentrations of virus than blood; therefore, the risk of infection via a bite wound is considerably less than injection/inoculation of infected blood, plasma or serum.

In the U.S., the Occupational Safety and Health Administration (OSHA) estimates that more than 5.6 million workers in health care and related occupations are at risk of occupational exposure to BBPs, including HIV, HBV, HCV, and other potentially infectious agents. Approximately 800,000 needle-stick injuries are reported in U.S. hospitals annually – one injury every 10 seconds. However, the number of occupational exposures is likely much higher than this. In Canada, Health Canada suggests that as many as 50% of injuries go unreported in both health-care and public safety settings.

Worldwide, unsafe injections are estimated to account for 30% of HBV infection, 31% of HCV infection, and 5% of HIV infections (WHO). Approximately, 500,000 deaths result each year from unsafe injection practices in medical settings. Reuse of syringes and needles in the absence of adequate sterilization exposes millions of people to infection – in some countries reuse of injection equipment is estimated at approximately 70%. Syringes and needles are often just rinsed in a pot of tepid (luke-warm) water between injections.

Disposal of dirty injection equipment also results in significant HCW exposure, and in some countries unsafe disposal of used equipment may lead to re-sale on the black market.

BBP infections are preventable in many cases. Prevention strategies include training of health care workers, HBV immunization, post-exposure prophylaxis and improved waste management.