HIV/AIDS: State of Washington Mandatory 2 Hour Training

Part 2. HIV Transmission and Infection Control


Part 1. Etiology and Epidemiology of HIV and AIDS

Part 5. Ethical and Legal Issues





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HIV and the Chain of Infection

HIV is a relatively fragile virus. It is not spread by casual contact. It is not easy to "catch"; it must be acquired. HIV is considered to be a fragile virus when exposed to air and room temperatures. Hepatitis B (HBV) and hepatitis C (HCV) are both considered "stronger" viruses that can remain infectious for a longer period of time. When these viruses are outside the human body, much depends on environmental factors such as heat, cold, exposure to oxygen, etc.). HBV and HCV will be discussed later in this course.

The Chain of Infection provides a model for understanding how any infection is spread. All of the components below must be present for an infection to occur.

The pathogenic microorganism is the microorganism that causes infection such as bacteria, viruses, fungi and parasites. There must be a sufficient dose of the organism, that is enough concentration and amount of the organism to cause infection.

The reservoir is the place where microorganisms live, such as in humans and animals, in soils, food, plants, air or water. The reservoir must meet the needs of the pathogen in order for the pathogen to survive and multiply.

The means of escape are how the microorganism leaves the reservoir.

The mode of transmission is how the microorganism moves from place to place.

The means of entry is how the micro-organism enters the host. There must be an adequate number of organisms to cause infection.

The host susceptibility is the person who may become infected.

All of these components together are considered to be the "chain of infection". In the healthcare setting, all of these factors come into play in the spread or the control of infection. There are effective strategies of infection control that will prevent infection transmission by interrupting one or more links in the chain of infection (CDC, 2007).

The following is how the chain of infection relates to HIV/AIDS:

  • The pathogenic microorganism is the human immune deficiency virus, or HIV. A sufficient dose, or concentration and amount, of HIV must be present for infection to occur.
  • The reservoir is blood or body fluids of the "source" patient; anyone with the virus can be an HIV source.
  • The means of escape are how the blood or body fluids of the source patient exit the source patient. This includes infected blood, semen, vaginal secretions or breast milk.
  • Mode of transmission is through direct contact with infected blood or body fluids noted above.
  • The means of entry is through the non-intact skin that can occur through unprotected sex, injecting drug use, and rarely splashing onto mucous membranes.
  • Host susceptibility is the person who may now become infected with HIV.
Case Study #1

Mr. R. is a middle-aged, married, Caucasian, male computer salesman who was transported to the ED after being found unresponsive in his apartment by a neighbor. Following a thorough exam the provider suspected a possible drug overdose, which was confirmed when a urine drug screen was positive for cocaine. Once stabilized, the staff offered him an HIV test. Mr. R. adamantly refused the test saying that he did not have any risk factors. The provider suspected this was not true and proceeded to perform a social history. Eventually, the provider was able to solicit answers that indicate Mr. R. is at risk for HIV: he has been sexually active since high school and has not always used condoms; while he is primarily heterosexual and has been married for almost 15 years, he has occasionally located men on the internet that he met for dates; he has never used intravenous drugs, but does share straws when using cocaine; he was incarcerated for assault when he was younger, and while in jail had used a common needle to give himself a tattoo.

Mr. R. thought that since he had only used drugs with people he knew and had sex with healthy looking men he did not have risk factors for HIV. He also thought that someone would have found out he was HIV positive during a recent hospital admission when he had labs drawn daily prior to and after major surgery.

The provider convinced Mr. R. that he should have an HIV test based on the results of his assessment. He provided him with education focusing on routes of transmission and appropriate barrier use. He explained the risk of having unprotected sexual relations and the fact that you cannot tell someone has HIV/AIDS by the way they look. The test results were negative, and the provider stressed the importance of retesting if he engaged in more high risk behaviors.

Continue to Part 2. HIV Transmission and Infection Control, Con't.