Bloodborne pathogens are microorganisms found in human blood that can cause disease in people. These infectious agents pose a risk when infected blood or certain other potentially infectious body fluids enter the bloodstream of another person. Transmission commonly occurs through percutaneous exposure, such as an accidental needlestick injury or a cut from contaminated sharp objects. Exposure can also happen when infected materials contact mucous membranes or open skin lesions.
Viral Bloodborne Pathogens
Viruses represent the most commonly recognized and concerning bloodborne pathogens due to their persistent nature and the severity of the diseases they cause. The most significant viral agents transmitted through blood are the Hepatitis B Virus (HBV), the Hepatitis C Virus (HCV), and the Human Immunodeficiency Virus (HIV). These viruses can establish long-term infections that lead to chronic illness and severe organ damage if left unmanaged.
Hepatitis B Virus (HBV) is a partially double-stranded DNA virus known for its stability, allowing it to survive outside the body on environmental surfaces for at least seven days. This makes it highly infectious; the risk of transmission following a percutaneous exposure can range from 6% to 30%. While an effective vaccine exists to prevent HBV infection, chronic infection can lead to liver cirrhosis and hepatocellular carcinoma.
Hepatitis C Virus (HCV) is an RNA virus that causes inflammation of the liver and frequently leads to chronic infection, affecting up to 85% of newly infected individuals. Unlike Hepatitis B, there is no vaccine available for HCV, although modern antiviral treatments can cure the infection in most people. HCV is the leading cause of liver transplantation in the United States.
The Human Immunodeficiency Virus (HIV) is a retrovirus that targets and destroys CD4+ T-lymphocytes, integral cells of the immune system. This destruction leads to Acquired Immunodeficiency Syndrome (AIDS), leaving the body vulnerable to opportunistic infections and certain cancers. Though the risk of transmission from a needlestick injury is relatively low (around 0.3%), HIV infection requires lifelong antiretroviral therapy to manage the viral load and preserve immune function.
Bacterial Bloodborne Pathogens
Certain bacteria can also be transmitted through blood exposure, though they are generally less common as occupational hazards in developed nations compared to major viruses. These agents are typically identified in specific circumstances, such as contaminated blood transfusions or exposures in specialized laboratory settings. Bacterial infections are often treatable with antibiotics, which can prevent the development of long-term disease.
One notable bacterial agent is Treponema pallidum, the spirochete responsible for syphilis. While sexual contact is the primary route of transmission, the bacterium can be passed through blood transfusions, which historically posed a risk before modern screening protocols were implemented. The organism circulates in the bloodstream during the primary and secondary stages of the disease.
Brucella species, which cause brucellosis, are recognized as bloodborne threats, particularly for laboratory personnel handling unsterilized cultures. Brucellosis is a zoonotic disease, primarily transmitted from animals to humans, but direct contact with infected blood or tissues can lead to human infection. This bacterium causes a systemic illness characterized by a fluctuating fever, and infection is a recognized risk in laboratory and occupational animal care environments.
Parasitic Bloodborne Pathogens
Parasites represent a diverse group of organisms, including protozoa and helminths, that circulate in the human bloodstream and can be transmitted through blood exposure. While many parasitic diseases are primarily vector-borne, they become bloodborne threats when infected blood is transferred directly to another person. These infections are often geographically restricted but remain a concern for global travelers and blood-banking systems.
The most recognized parasitic bloodborne pathogen is Plasmodium species, the protozoa responsible for malaria. The parasite infects and multiplies within red blood cells, and transmission through contaminated blood products or shared needles is a serious consideration, especially in non-endemic regions. Malaria can cause severe, life-threatening illness due to the destruction of red blood cells.
Another significant protozoan is Trypanosoma cruzi, the agent of Chagas disease, which is endemic to Central and South America. Although typically transmitted by the triatomine “kissing” bug, the parasite can be transmitted through blood transfusion or organ transplantation. Screening for T. cruzi is an important measure in blood banks to prevent transmission.