Exposure Control Plan for Bloodborned pathogens

Universal Precautions are designed to prevent the spread of microorganisms among persons. Using Universal Precautions interrupts the chain of infection. Spread of infection requires three elements: a source of infecting organisms, a susceptible host, and a means of transmission for the organism.

The source of the infecting agent may be employees, students, research animals or materials, or visitors, and may include persons with acute disease, persons in the incubation period of the disease, or persons who are colonized by the infectious agent but have no apparent disease. Another source of infection can be the person's own endogenous flora (autogenous infection). Other potential sources are inanimate objects in the environment that have become contaminated, including equipment, medications, and laboratory cultures.

Resistance to pathogenic microorganisms varies greatly. Some persons may be immune to or able to resist colonization by an infectious agent; others exposed to the same agent may establish a commensal relationship with the infecting organism and become asymptomatic carriers; still others may develop clinical disease. Persons with diabetes mellitus, lymphoma, leukemia, neoplasia, granulocytopenia, or uremia and those treated with certain antimicrobials, corticosteroids, irradiation, or immunosuppressive agents may be particularly prone to infection. Age, chronic debilitating disease, shock, coma, traumatic injury, or surgical procedures also make a person more susceptible to infection.

Microorganisms are transmitted by various routes and the same microorganisms may be transmitted by more than one route. For example, varicella-zoster virus can spread either by the airborne route (droplet nuclei) or by direct contact.

There are four main routes of transmission - contact, airborne, vehicle, and vectorborne.

Contact transmission, the most important and frequent means of transmission of infections, can be divided into three subgroups: direct contact, indirect contact, and droplet contact.
1. Direct Contact - This involves direct physical transfer between a susceptible host and an infected or colonized person, such as occurs when patient-care personnel turn patients, give baths, change dressings or perform other procedures requiring direct personal contact. Direct contact can also occur between two individuals, one serving as the source of infection and the other as a susceptible host.
2. Indirect Contact - This involves personal contact of the susceptible host with contaminated intermediate objects, usually inanimate, such as bed linens, clothing, instruments, and dressings.
3. Droplet Contact - Infectious agents may come in contact with the conjunctivae, nose, or mouth of a susceptible person as a result of coughing, sneezing, or talking by an infected person who has clinical disease or is a carrier of the organism. This is considered "contact" transmission rather than airborne because droplets usually travel no more than about three feet.
Airborne transmission occurs by dissemination of either droplet nuclei (residue of evaporated droplets that may remain suspended in the air for long periods of time) or dust particles in the air containing the infectious agent. Organisms carried in this manner can be widely dispersed by air currents before being inhaled by or deposited on the susceptible host.
The vehicle transmission route applies in diseases transmitted through these contaminated items:
1. Food, such as in salmonellosis;
2. Water, such as in legionellosis;
3. Drugs, such as in bacteremia resulting from infusion of a contaminated infusion product;
4. Blood, such as in hepatitis B virus (HBV) or HIV infection.
Vectorborne transmission is the transfer of pathogenic microorganisms from a living agent (e.g., arthropods such as ticks, fleas, or lice, or vertebrates such as dogs or rats) to the human host, usually by means of parenteral inoculation (biting). Examples of these diseases are Lyme disease, bubonic plague, and Rocky Mountain spotted fever.