California Dental Board Approved: Infection Control (2 Units)

Preventing Transmission of Bloodborne Pathogens






 

Bloodborne viruses such as hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV) are of concern to dental health care professionals (DHCP). These viruses:

  • Can be transmitted to patients and DHCP in healthcare settings.
  • Can produce chronic infection.
  • Are often carried by persons unaware of their infection.

Transmission of bloodborne pathogens may occur from patient to DHCP, from DHCP to patient, and from patient to patient. Because DHCP frequently are exposed to blood and blood-contaminated saliva during dental procedures, they are at greater risk of infection by a bloodborne pathogen than are patients.

The risk of infection with a bloodborne virus is largely determined by:

  • Its prevalence, or frequency, in the patient population.
  • The risk of transmission after an exposure to blood (risk varies by type of virus).
  • The type and frequency of blood contacts.If health care personnel are frequently exposed to blood, especially if they are working with sharp objects such as needles, their risk of exposure to a bloodborne virus is higher than if they rarely come into contact with blood.

Characteristics of Percutaneous Injuries Among DHCP

According to the CDC (2003), available information indicates that percutaneous injuries among dentists declined from an average rate of 11 injuries per year in 1987 to <3 injuries per year in 1993.

In general, most injuries among general dentists were caused by burs, followed by syringe needles and other sharp instruments. Injuries most often occur while the dentist's hands are outside the patient's mouth. Most injuries involve small, rather than large, amounts of blood.

The frequency of percutaneous injuries among oral surgeons is similar to that reported among U.S. dentists. Injuries among oral surgeons may occur more frequently during procedures using surgical wire, such as during fracture reductions.

Average Risk of Bloodborne Virus Transmission after Needlestick (CDC, 2003)
Source
Risk

HBV

HBsAg+ and HBeAg+

HBsAg+ and HBeAg



- 22.0%-31.0% clinical hepatitis; 37%-62% serological evidence of HBV infection.

1.0%-6.0% clinical hepatitis; 23%-37% serological evidence of HBV infection

HCV 1.8% (0%-7% range)
HIV 0.3% (0.2%-0.5% range)

The average risk of transmission after a single needlestick from an infected patient by type of bloodborne virus varies greatly by type of virus.

For instance, the risk of HBV transmission after a percutaneous exposure (e.g., needlestick) to HBV-infected blood varies from 1%-62%, depending on the hepatitis B e-antigen (HBeAg) status of the source patient. If the source patient's blood is positive for HBeAg (a marker of increased infectivity), the risk of transmission can be as high as 62%. If the patient's blood is hepatitis B surface antigen (HBsAg) positive but HBeAg negative, the risk varies from 1%-37%.

The average risk of HCV transmission after a percutaneous exposure to HCV-infected blood is 1.8%.

The average risk of HIV infection after a percutaneous exposure to HIV-infected blood is 0.3%. To put this in perspective, 1 in 3 needlesticks from an HBeAg+ source patient would result in infection compared to only 1 in 300 needlesticks from an HIV-infected patient.

As mentioned earlier, one factor to consider in assessing the risk of infection is the type of body substances to which DHCP are exposed. This slide shows the concentration of HBV in various body fluids. On the left, in red, are the fluids with the highest concentration of virus.

Moving from the left to the right side, the concentration decreases. Blood, for instance, has a higher virus concentration than urine or sweat. Saliva alone, without blood, has a moderate concentration of virus.

Transmission of bloodborne pathogens (e.g., HBV, HCV, and HIV) in dental health care settings is rare, any incidence of exposure can have serious consequences. Exposure to infected blood can result in transmission from patient to dental professional and from dental professional to patient, and from one patient to another. The opportunity for transmission is greatest from patient to dental professionals, who frequently encounter patient blood and blood-contaminated saliva during dental procedures.

No transmission of HIV from dental professionals to patient has been reported since 1992 (CDC, 2003). The last HBV transmission from dental professional to patients was reported in 1987. No transmission of HCV from dental professional to patient has been reported.

The majority of dental professionals infected with a bloodborne virus do not pose a risk to patients because they do not perform activities meeting the necessary conditions for transmission. For dental professionals to pose a risk for bloodborne virus transmission to patients, the dental professional must (CDC, 2003):

  1. Be viremic (i.e., have infectious virus circulating in the bloodstream);
  2. Be injured or have a condition (e.g., weeping dermatitis) that allows direct exposure to their blood or other infectious body fluids; and
  3. Enable their blood or infectious body fluid to gain direct access to a patient's wound, traumatized tissue, mucous membranes, or similar portal of entry.

Although an infected dental professional might be viremic, unless the second and third conditions are also met, transmission cannot occur.

The risk of occupational exposure to bloodborne viruses by the dental professional, from patients, is largely determined by the viral prevalence in the patient population and the nature and frequency of contact with blood and body fluids through percutaneous or permucosal routes of exposure (CDC, 2003). The risk of infection after exposure to a bloodborne virus is influenced by (CDC, 2003):

  • Inoculum size,
  • Route of exposure, and
  • Susceptibility of the exposed dental professional.

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