Bloodborne pathogens are disease-causing microorganisms carried in human blood. The term covers any virus, bacterium, or parasite that can spread from one person to another through contact with infected blood or certain body fluids. The most well-known examples are hepatitis B (HBV), hepatitis C (HCV), and HIV, but the full list includes dozens of organisms ranging from syphilis to Ebola.
OSHA formally defines bloodborne pathogens as “pathogenic microorganisms that are present in human blood and can cause disease in humans,” and federal workplace safety regulations exist specifically to limit exposure in jobs where blood contact is possible.
The Three Major Bloodborne Pathogens
Hepatitis B (HBV)
Hepatitis B is the most resilient and easily transmitted of the three major bloodborne viruses. It can survive on dry surfaces, such as countertops, equipment, or dried blood spots, for at least seven days and still remain infectious. A single needlestick from an HBV-positive source carries a transmission risk that can range from 6% to over 30%, depending on the viral load of the source. That makes HBV far more contagious per exposure event than either hepatitis C or HIV.
The good news is that an effective vaccine exists. OSHA requires employers to offer the hepatitis B vaccine, at no cost, to any employee with occupational exposure to blood. The vaccine must be offered within 10 days of an employee’s initial assignment to such a role. Workers who decline must sign a declination form, but they can change their mind later and still receive the vaccine free of charge as long as they remain in an exposed role.
Hepatitis C (HCV)
Hepatitis C attacks the liver, and about half of people who become infected develop a chronic, long-term infection. In the United States, most new HCV infections happen through sharing needles or other drug-injection equipment. It can also pass from mother to baby during pregnancy or birth, and rarely through sexual contact.
There is no vaccine for hepatitis C. However, antiviral treatments developed in the last decade can cure the vast majority of chronic infections, which makes early detection critical. Occupational transmission through needlestick injuries is less common than with HBV but still a real concern.
HIV
HIV carries a lower per-exposure transmission risk than either hepatitis virus in occupational settings. After a needlestick involving blood from an HIV-positive source, the estimated risk of infection (without preventive treatment) is approximately 0.2% to 0.3%. For a mucous membrane splash, such as blood contacting the eyes or mouth, the risk drops to roughly 0.09%. Those numbers are small, but the consequences of infection are lifelong, which is why post-exposure protocols are taken seriously.
Other Organisms Carried in Blood
HBV, HCV, and HIV get the most attention, but they are not the only bloodborne threats. OSHA recognizes a broader category called “other potentially infectious materials” (OPIM) that includes additional pathogens. Among them are cytomegalovirus (CMV), Epstein-Barr virus (the virus behind mono), Zika virus, and human parvovirus B19. Less commonly encountered bloodborne organisms include the bacteria that cause syphilis, the parasites responsible for babesiosis, agents of brucellosis, and viruses that cause hemorrhagic fevers like Ebola and Marburg.
Some of these are rare in everyday healthcare. Others, like CMV, are extremely common but typically only dangerous for people with weakened immune systems or during pregnancy. The point of the “bloodborne pathogen” category is that any blood exposure carries some degree of unpredictable risk.
How Transmission Happens
Bloodborne pathogens need a way into the body. The most common routes are:
- Needlestick or sharps injuries: A puncture from a contaminated needle, scalpel, or broken glass is the highest-risk occupational exposure.
- Mucous membrane contact: Blood or infectious fluid splashing into the eyes, nose, or mouth.
- Non-intact skin: Open cuts, abrasions, chapped or cracked skin, or areas affected by dermatitis can absorb pathogens from contaminated fluids.
- Shared injection equipment: Outside the workplace, sharing needles or syringes is the most common route for hepatitis C transmission in the U.S.
Blood is the primary concern, but other fluids are also considered potentially infectious. These include semen, vaginal secretions, cerebrospinal fluid, synovial fluid (from joints), pleural fluid (from the chest cavity), and any body fluid visibly contaminated with blood. Sweat, on its own, is not considered infectious.
How Exposure Is Prevented
The core prevention strategy is called “standard precautions,” a system introduced by the CDC in 1996 that treats all blood and body fluids from every patient as potentially infectious, regardless of diagnosis or appearance. This replaced an earlier, narrower framework called “universal precautions” that focused only on bloodborne pathogens. Standard precautions expand the concept to cover all body fluids (except sweat), non-intact skin, and mucous membranes.
In practice, standard precautions come down to barrier protection and safe handling:
- Gloves whenever contact with blood, body fluids, mucous membranes, or broken skin is expected.
- Masks and eye protection (or a face shield) during procedures that could generate splashes or sprays.
- Gowns when clothing could become contaminated.
- Safe sharps handling: Never recapping needles, using puncture-resistant disposal containers, and employing safety-engineered devices when available.
Engineering controls matter as much as personal equipment. Self-sheathing needles, splash guards, and designated sharps containers remove the hazard before it reaches the worker.
What Happens After an Exposure
If blood or infectious fluid contacts a wound, broken skin, or mucous membrane, the first step is immediate decontamination. Skin wounds should be washed thoroughly with soap and water. Eyes or mouth should be flushed with clean water. The exposure should then be reported right away, because the treatments that prevent infection work best when started as soon as possible.
For HIV exposures, post-exposure prophylaxis (PEP) is a course of antiviral medication that can prevent the virus from establishing infection. There is no precisely defined cutoff for when PEP stops working, but animal research suggests effectiveness drops significantly after 24 to 36 hours. Current guidelines recommend starting PEP even if more than 36 hours have passed, because some benefit may still exist. For hepatitis B, unvaccinated workers may receive both the vaccine and an immune globulin injection. There is no equivalent preventive treatment for hepatitis C, so monitoring and early detection become the priority.
Cleaning Up Blood Spills
Proper decontamination of surfaces matters because some pathogens, particularly hepatitis B, remain infectious on surfaces for days. The CDC recommends a diluted bleach solution for blood spill cleanup, but the concentration depends on the size of the spill.
For small spills (a few drops on a hard surface), a 1:100 dilution of standard household bleach is sufficient. For large spills, the surface needs to be cleaned first to remove visible blood, since organic material inactivates disinfectants. After cleaning, a stronger 1:10 bleach solution should be applied. If there is any chance of a sharps injury in the spill area (broken glass, for instance), the surface should be decontaminated before anyone begins cleaning, then cleaned and disinfected again with the 1:10 solution. EPA-registered hospital disinfectants labeled as effective against tuberculosis are also acceptable alternatives to bleach.
Who Needs to Know This
OSHA’s Bloodborne Pathogens Standard applies to any employee who could reasonably encounter blood or OPIM as part of their job. That obviously includes nurses, doctors, and paramedics, but the reach extends further: laboratory technicians, dental hygienists, housekeeping staff in medical facilities, tattoo artists, correctional officers, and school nurses all fall under the standard. Employers in covered workplaces must provide training, protective equipment, and a written exposure control plan at no cost to employees.
Outside of regulated workplaces, the same biology applies. Anyone who might encounter another person’s blood, whether as a caregiver, coach, or first responder at an accident scene, benefits from understanding how these pathogens spread and how simple barriers like gloves dramatically reduce risk.