Infectious Disease and Occupational Risk
Occupational exposure to infectious diseases is an everyday risk that prehospital care personnel encounter. Accordingly, it is important to have a thorough working knowledge of infection control and occupational risk in order to avoid missing work days from common illnesses, such as the flu. More importantly, such knowledge will help prevent the possibility of contracting more serious illnesses, such as tuberculosis, hepatitis, and HIV/AIDS.
While the chance of contracting these more serious illnesses is low, they still pose a very real risk – as of December 2002, there have been 12 cases of possible occupationally-acquired HIV/AIDS infection in paramedics/EMTs.1 Increasing your knowledge of potential sources of infection and infectious agents, as well as their modes of transmission and portals of entry, will allow you to work safely without undue fear or anxiety.
The Chain of Infection:
The development of an infectious disease typically progresses through a “chain of infection.”2
-The Infectious Agent:
The chain begins with an infectious agent, which is capable of producing a disease.
The next link is the environment in which the agent lives. This is known as the agent’s reservoir, which can be a person or object.
-The Portal of Exit:
The third link in the chain of infection involves the way the object exits its reservoir.
The agent must leave the object in order to be picked up by a new host. The action of leaving the reservoir and entering a new host is known as transmission. This can occur through the release of respiratory droplets by coughing or sneezing, for example.
****KEY POINT: The mode of transmission is a focal point in preventing the spread of infection.
-The Portal of Entry:
In order to be transmitted, the infectious agent must have a portal of entry into a susceptible host. The portal of entry is typically the same point from which the agent exited its reservoir. For example, if an agent was excreted by the mouth of the source host, it is likely to enter the new host through the mouth, as well.
-A Susceptible Host:
A susceptible host is the final link in the chain. Susceptibility varies from person to person, according to the person’s immune status.
For transmission to occur, a significant exposure must take place. This may involve exposure by a contaminated needlestick or being cut with a sharp object. Contamination can also occur through a splash of infectious fluid on the mucous membranes, including the mouth, eyes, and nose. Less commonly, transmission can occur by a splash onto non-intact skin.
The risk of infection depends on the type of substance, the route of exposure, the volume of fluid involved, the severity of the exposure, the pathogen involved, the immune status of the healthcare worker, the severity of the infection in the source, and whether post-exposure prophylaxis was instituted.
-Risk of Human Immunodeficiency Virus Transmission:
The risk of HIV transmission to a healthcare worker, who suffers a needlestick from an HIV positive source, is around 0.3%. This risk is increased when there is a large volume of blood involved, when there is a deep penetration, and when the source patient has a high viral load. The risk of HIV transmission from exposure of mucous membranes to a splash with infectious bodily fluids is 0.09%.
-Risk of Hepatitis C Virus Transmission:
The risk of HCV transmission to a healthcare worker, who suffers a needlestick exposure from an HCV positive patient, is around 3%. Exposure of mucous membranes and non-intact skin has not been quantified.
-Risk of Hepatitis B Virus Transmission:
The risk of contracting HBV from an HBV positive source is 30% in an unvaccinated healthcare worker.3
Factors Which Alter Risk:
Deep injury, visible blood on the device of transmission, a device that just came directly from a vein or artery, and terminal illness in the source patient are factors that are associated with an increased risk of contracting disease.
Wearing gloves, shallow injuries, and having a solid needle as the device of transmission are associated with a decreased risk of contracting disease.3