Bloodborne pathogens and universal precautions

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 percent 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

OSHA's Bloodborne Pathogens standard calls the higher-risk fluids "other potentially infectious materials" (OPIM). It also treats any body fluid as OPIM when it is difficult or impossible to tell whether it contains blood. Fluids in the lower-risk column can still carry other infections, such as norovirus in stool and vomit.

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.

Universal and standard precautions

Universal precautions, introduced by the CDC in 1987 in response to HIV, means treating all human blood and certain body fluids as if they were known to be infectious for bloodborne pathogens. It is the approach OSHA's Bloodborne Pathogens standard requires. In health care, the CDC expanded it in 1996 into standard precautions, which apply to all blood, body fluids except sweat, non-intact skin and mucous membranes, and cover contact-spread organisms as well as bloodborne ones. Outside health care, universal precautions remains the usual term. The 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

OSHA's Bloodborne Pathogens standard (29 CFR 1910.1030) requires every covered employer to have a written exposure control plan that is accessible to workers and reviewed at least once a year. The plan must:

• list job classifications in which all or some workers have occupational exposure, and the tasks involved;
• describe the schedule and method for implementing engineering and work practice controls, protective equipment, housekeeping, regulated waste, hepatitis B vaccination, post-exposure evaluation, training and recordkeeping;
• document the annual consideration and use of safer medical devices, with input from front-line workers who are responsible for direct patient care;
• include the procedure for evaluating exposure incidents.

Employers must also keep a sharps injury log (if they are required to keep OSHA injury records), train workers at hire and every year thereafter during working hours, provide protective equipment at no cost, and keep medical records confidentially for the duration of employment plus 30 years.

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 percent 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.

The Bloodborne Pathogens standard requires employers to make the hepatitis B vaccine series available at no cost, at a reasonable time and place, within 10 working days of initial assignment to a job with occupational exposure, unless the worker has already been vaccinated, is immune or has a medical reason not to receive it. Workers who decline must sign the declination statement in Appendix A of the standard, and the employer must provide the vaccine if they later change their mind.

# 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 behavior. 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.