Infection Control for Dental Professionals: The California Requirement _______________________________
COMMON MODES OF INFECTION TRANSMISSION
Category
Definition
Direct contact Person-to-person transmission of pathogens (e.g., through skin, blood, or body fluid contact). Indirect contact An intermediate person or item acts as a transport between the portal of exit in one person and the portal of entry to the next person (e.g., via unwashed hands, shared equipment, needlesticks). Droplets a Large respiratory droplets propelled by an infected person coughing, sneezing, talking, or breathing heavily. Droplets settle rapidly within 6 feet of the individual on surfaces and in the upper airway of individuals exposed via the eyes, nose, or mouth.
Small particles or micro-droplets are released into the air by an infected person coughing, sneezing, talking, or breathing heavily. Airborne pathogens can linger for long periods of time and travel longer distances, landing on surfaces and being breathed in by other individuals into the lower airway. Contact with a contaminated inanimate object (e.g., used gloves, pens, used tissues, soiled laundry, keyboards, furniture). Water may be contaminated by micro-organisms in dental water unit lines, causing patient contamination as well as dispersing infected airborne particles and droplets.
Airborne (aerosols) a
Fomites
Water
a In 2024, a global consensus was reached to replace the terms droplet, airborne, and aerosol with a general umbrella term of “through the air transmission,” regardless of infected respiratory particle size and/or distance traveled. Source: [5; 6; 8] Table 1
hepatitis C or hepatitis B virus has resulted from using the same syringe or vial to administer medication to more than one patient, even if the needle was changed [5; 10]. The prevalence of hepatitis C virus infection among dentists and surgeons is similar to that among the general population, approximately 1% to 2% [5]. No studies of transmission from hepatitis C virus-infected DHCP to patients have been reported, and the risk for such transmission appears limited [10]. HIV/AIDS The average risk of HIV infection after a needlestick or cut exposure to HIV-infected blood is 0.3%; 99.7% of needle- stick or cut exposures do not lead to infection. The risk after exposure of the eye, nose, or mouth to HIV-infected blood is estimated to be 0.1%. There have been no documented cases of HIV transmission due to an exposure involving a small amount of blood on intact skin (i.e., a few drops of blood on skin for a short period of time) [5; 10]. In the United States, the risk of HIV transmission in dental settings is extremely low. According to surveillance data from 1981 to 2013, a total of 58 cases of HIV seroconversion had been documented among healthcare personnel after occupa- tional exposure to a known HIV-infected source, but none were among dental care personnel [12]. Certain factors affect the risk of HIV transmission after an occupational exposure. Laboratory studies have determined if needles that pass through latex gloves are solid rather than hollow-bore or are of small gauge (e.g., anesthetic needles), less blood is transferred. In a retrospective, case-control study of healthcare personnel, an increased risk for HIV infection was associated with exposure to a relatively large volume of blood, as with a deep injury with a device that was visibly
contaminated with the patient’s blood or a procedure that involved a needle placed in a vein or artery [12]. The risk was also increased if the exposure was to blood from patients with terminal illnesses, possibly reflecting the higher titer of HIV in patients with late-stage AIDS. AEROSOLS, DROPLETS, AND SPLATTER Aerosols, droplets (produced by the respiratory tract), and splat- ter contaminated with blood and bacteria are produced during many dental procedures. Devices such as dental handpieces, ultrasonic and sonic scalers, air polishers, air-water syringes, and air abrasion units produce visible aerosol clouds and possible airborne contamination. Splatter generated by dental procedures such as drilling is a primary risk for transmission of bloodborne pathogens. In general, because of their smaller size, aerosols pose the greatest risk for airborne infection [9]. Several studies have shown that airborne or droplet nuclei may extend up to 6 feet away from the source and can remain airborne for up to 30 minutes after a procedure. Tuberculosis (TB) is of special concern because it is a large particle that can remain airborne or can dry on a surface and become airborne again as part of a dust particle. In 2024, the World Health Organization (WHO) and the Centers for Disease Control and Prevention from the United States, China, Europe, and Africa, published a global consen- sus of the terminology for pathogens that transmit through the air. Key changes include [8]: • Any infected particles that are expelled from an individual through nose or mouth are referred to as “infectious respiratory particles” (IRPs). • IRPs exist on a spectrum of sizes and should no longer be distinguished as “small” (aerosol) or “large” (droplet).
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