Bloodborne pathogens and routine practices

Bloodborne pathogens are infectious agents carried in blood and some other body fluids that can cause disease when they enter another person's bloodstream or mucous membranes. The three that matter most at work are hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV). Workers in health care, dentistry, personal services, laboratories, first response, corrections, cleaning, waste handling and even teaching and office first aid can be exposed. This lesson explains the pathogens, the body fluids that carry them, how they are transmitted at work, and the core practice of treating all blood and body fluids as potentially infectious.

The three main bloodborne pathogens

Hepatitis B virus infects the liver. Many adults clear the infection, but some develop chronic infection that can lead to cirrhosis and liver cancer years later. HBV is far more infectious than HIV: it is present in very high concentrations in the blood of infected people and can survive in dried blood on surfaces for at least seven days. Before vaccination became routine for health care workers, thousands of them were infected every year in North America, and hundreds died. A safe, highly effective vaccine has been available since the 1980s.

Hepatitis C virus also infects the liver and becomes chronic in most people who are infected, often without symptoms for decades. There is no vaccine, but modern direct-acting antiviral medicines cure more than 95 per cent of infections after a course of 8 to 12 weeks. Early detection after an exposure therefore matters.

Human immunodeficiency virus attacks the immune system and, untreated, leads to AIDS. Modern antiretroviral treatment lets people with HIV live long, healthy lives, and people whose viral load is suppressed by treatment do not transmit HIV sexually. After a workplace exposure, post-exposure prophylaxis (PEP), started as soon as possible and ideally within two hours, greatly reduces the chance of infection. Occupational HIV infection is now extremely rare in North America.

Other bloodborne pathogens include syphilis, malaria, viral hemorrhagic fevers such as Ebola, and others, but these are much less common workplace risks in Canada and the United States.

Which fluids carry the risk

Fluids in the lower-risk column can still carry other infections, such as norovirus in stool and vomit, so routine practices still apply to them.

How exposure happens at work

Transmission at work needs infected blood or fluid to reach the bloodstream or a mucous membrane. The main routes are:

• percutaneous injuries: needlesticks, cuts from scalpels, broken glass or other sharp objects contaminated with blood;
• mucous membrane exposures: splashes of blood or fluid into the eyes, nose or mouth;
• non-intact skin exposures: contact with skin that is chapped, abraded, cut or affected by dermatitis;
• bites that break the skin, in rare cases.

Intact skin is an excellent barrier, so blood on unbroken skin is not considered an exposure, although it should be washed off promptly. Hollow-bore needles that have been in a vein or artery carry the highest risk because they hold more blood than solid needles or suture needles.

The size of the risk

The chance of infection after a single needlestick from an infected source varies by pathogen. Estimates from older studies, often cited by public health agencies, are summarized below; actual risk depends on the amount of blood, the source's viral load, the depth of the injury and the exposed worker's immunity.

# Expected infections from 100 needlesticks in a year, by source status (illustrative)
needlesticks = 100
share_source_positive = {"hepatitis B": 0.01, "hepatitis C": 0.02, "HIV": 0.005}
risk_per_stick = {"hepatitis B (non-immune)": 0.20, "hepatitis C": 0.018, "HIV": 0.003}
for (name, prev), (label, risk) in zip(share_source_positive.items(), risk_per_stick.items()):
    expected = needlesticks * prev * risk
    print(f"{label:<26} sources positive {prev:.1%}, risk {risk:.1%}: expected {expected:.3f} infections")
print("vaccinated responders: hepatitis B risk is close to zero")

hepatitis B (non-immune)   sources positive 1.0%, risk 20.0%: expected 0.200 infections
hepatitis C                sources positive 2.0%, risk 1.8%: expected 0.036 infections
HIV                        sources positive 0.5%, risk 0.3%: expected 0.002 infections
vaccinated responders: hepatitis B risk is close to zero

The expected numbers are small, which is the point: most individual needlesticks do not cause infection. But needlesticks are common, the consequences of infection can be lifelong, the anxiety for the worker is real, and the follow-up costs time and money. Every exposure must be prevented where possible and followed up when it happens.

Routine practices

Routine practices are the Canadian term for the infection prevention practices used with every person, every time, whether or not they are known or suspected to have an infection. The idea dates from the 1980s, when the term universal precautions was introduced in response to HIV: because you cannot tell who is infected, treat all blood and certain body fluids as potentially infectious. Routine practices extend that idea to all body fluids, non-intact skin and mucous membranes, and to contact-spread organisms as well as bloodborne ones. Their core elements are:

• a point-of-care risk assessment before each interaction or task: what am I likely to be exposed to, and what do I need?
• hand hygiene (lesson 4);
• personal protective equipment chosen by the risk assessment: gloves for contact with blood, body fluids or contaminated items; gowns when clothing may be soiled; eye and face protection when splashes or sprays are possible;
• safe handling and disposal of sharps (lesson 9);
• respiratory etiquette;
• cleaning and disinfection of equipment and surfaces (lesson 5);
• safe handling of soiled linen and waste;
• placement of patients or clients in a way that reduces risk to others.

The exposure control plan

Where workers may be exposed to blood or body fluids, employers should have a written plan, and in several provinces this is a legal requirement for health care or for workers at risk of exposure to infectious materials. A typical plan:

• identifies the jobs and tasks with a risk of exposure;
• describes the controls: safety-engineered sharps, sharps containers, work practices, protective equipment, cleaning and waste handling;
• sets out hepatitis B vaccination for exposed workers;
• describes the exposure response and post-exposure follow-up process (lesson 9);
• covers training, records and annual review, including the evaluation of safer devices with front-line workers.

Hepatitis B vaccination and immunity

Hepatitis B vaccine is given as a series, usually three doses over six months, or two doses for one newer adjuvanted product. About 90 to 95 per cent of healthy adults develop protective immunity. Because some people do not respond, health care workers and others at ongoing risk of blood exposure should have their antibody level (anti-HBs) checked one to two months after completing the series; a level of at least 10 mIU/mL indicates protection. People who do not respond receive a second series and are retested; those who still do not respond are counselled about their status and need prompt immune globulin after any exposure. Once a person has shown a protective response, booster doses are not routinely recommended for healthy workers, because immune memory persists even when antibody levels later fall.

Employers in health care and other higher-risk sectors usually offer the vaccine at no cost, and some provinces fund it for health care workers and students. Workers who decline should sign an informed declination after receiving information, and can change their mind later.

# Hepatitis B vaccine response and testing in a group of 200 new health care staff (illustrative)
staff = 200
respond_first_series = 0.92
respond_second_series = 0.60     # share of first-series non-responders who respond to a second series
nonresp1 = staff * (1 - respond_first_series)
resp2 = nonresp1 * respond_second_series
nonresp_final = nonresp1 - resp2
print(f"protected after first series: {staff * respond_first_series:.0f}")
print(f"non-responders retested after second series: {nonresp1:.0f}, of whom {resp2:.0f} respond")
print(f"persistent non-responders needing advice and prompt post-exposure care: {nonresp_final:.0f}")

protected after first series: 184
non-responders retested after second series: 16, of whom 10 respond
persistent non-responders needing advice and prompt post-exposure care: 6

Engineering and work practice controls

Most bloodborne exposures can be prevented by controls that do not depend on perfect behaviour. The most important are safety-engineered sharps, such as retractable needles, shielded needles, needleless connectors for intravenous lines and blunt suture needles where suitable; puncture-resistant sharps containers placed close to where sharps are used; and work practices such as never recapping used needles by hand, not passing sharps hand to hand in procedures (use a neutral zone instead), and disposing of sharps immediately after use. Lesson 9 covers sharps in detail.

Other work practices include not eating, drinking, applying cosmetics or handling contact lenses where exposure is possible; not storing food in refrigerators with blood or specimens; minimizing splashing and spraying; using mechanical pipetting in laboratories; and placing specimens in leak-proof containers for transport.