HIV/AIDS: State of Washington Mandatory 4 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.

Occupational Transmission

To date, there have been less than a dozen known cases of HIV transmission that have occurred in household settings in the U.S. and other countries. Reports of these cases have been thoroughly investigated by the CDC. The researchers determined that the transmissions were caused by sharing a razor contaminated with infected blood, the exposure of infected blood to cuts and broken skin, and possibly deep kissing involving a couple who both had bleeding gums and poor dental hygiene. It is important to remember that these cases were extremely unusual. Sensible precautions with bleeding wounds and cuts and not sharing personal hygiene items would have prevented these cases of infection.

There are also isolated cases of transmission from healthcare workers to patients.

How HIV is NOT Transmitted

No cases of HIV transmission have been linked to sharing computers, food, telephones, paper, water fountains, swimming pools, bathrooms, desks, office furniture, toilet seats, showers, tools, equipment, coffee pots or eating facilities However, personal items, which may be contaminated with blood, including but not limited to razors, toothbrushes and sex toys, should not be shared.

There have been no cases of HIV transmission by children playing, eating, sleeping, kissing and hugging.

Biting poses very little risk of HIV transmission. The possibility only exists if the person who is biting and the person who is bitten have an exchange of blood (such as through bleeding gums or open sores in the mouth.) Bites may transmit other infections, and should be treated immediately by thoroughly washing the bitten skin with soap and warm water, and disinfecting with antibiotic skin ointment.

Case Study #2

Ms. P. decided to have an HIV test after finding out that an old boyfriend had HIV. She was shocked to hear the news at first and went to the testing clinic knowing there was a chance of infection, but she was confident that she was in good health overall, and had not been sick or had any unusual symptoms. She had dated this boyfriend for about 3 months at least six years ago but they just didn't "click." Eventually, they went their own ways and began dating other people. Several years ago she moved to a nearby city and changed jobs. She only found out about his illness by chance when she happened to meet a mutual friend at an art festival.

When the test results came back positive she could not believe it at first. Then, all at once, she began to think about men she had been involved with since. How many had she infected?

Ms. P. was given an appointment at an HIV treatment center to discuss the need for antiretroviral therapy. Before beginning therapy, the provider ordered a genotype test to identify any possible viral resistance she might have. When the results were back, she was informed that she had been infected with a strain of virus that was multi-drug resistant (MDR). In other words, many of the commonly used medications for HIV would not provide effective treatment. The provider also explained that infection with HIV that is MDR is more common than many people realize. In one recent study in NY City, 10% of people newly diagnosed with HIV had MDR, and more than 25% had at least some resistance (Shet et al., 12th CROI, 2005). Medications would need to be carefully selected to provide the best treatment possible. Even so, infection with a strain of MDR HIV makes progression to AIDS and death more likely.

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