Course: BIS 105 Environmental Biology

Unit 3 Learning Module

Evolution

Case Study

In January 1995 a nurse by the name of Janice Trahan discovered she was HIV positive after her gynecologist ran blood tests due to indications of a viral infection. Since she is a nurse she is at a higher risk of infection because of her contact with patients and needles. However, she was not aware of any incidents that may have resulted in her infection and did not believe that was how she became infected. She suspected her ex-boyfriend, Richard Schmidt, even though he was not infected.

Richard Schmidt, a doctor, had an affair of ten years with Janice until July 1994 when she broke off the relationship. He does not personally have HIV, so why would Janice suspect him of being the source of her infection? She has a rare condition known as chronic fatigue syndrome. There is no cure for this condition, but one of the frequent treatments to reduce the symptoms is a vitamin B_12 injection that Richard had administered during their relationship. On August 4, Richard called Janice to say he was stopping by to give her another injection.

Janice believed this may have been how she was infected with HIV, but since Richard is not infected how could he infect her? She accused him of obtaining contaminated blood samples from an HIV infected patient and then injecting her. HIV is not stable outside of the body for more than a few hours so this had to occur within a short time period. Investigators began looking through records of Richard's patients. They discovered a few irregularities. When they went looking for the laboratory log book, the one for the date in question was "missing." After further examination it was found to have been placed with log books from a decade earlier. In addition, a blood withdrawal on August 4th did not have an accession sticker associated with the withdrawal to track the samples being sent for testing, there was just a note it was for Dr. Schmidt. When prosecutors interviewed this patient, Donald McClelland, he testified that it wasn't a scheduled visit, he had been called into the office for a blood withdrawal. In addition, he was infected with HIV that had progressed to AIDS.

Investigators are definitely suspicious of Richard at this point, but most of the evidence is circumstantial. It is months after the injection in question occurred, so there is no chance of finding the contaminated needle. How can they prove beyond a reasonable doubt that he was the source of infection? To do this, they decided to do what is called a phylogenetic analysis. Samples of genetic information are sequenced to see how similar they are to one another. With a rapidly mutating virus like HIV, each person develops their own suite of unique viruses over time because of mistakes that are made when the virus is replicated. However, if the analysis is done soon after infection, there is little time for changes to have occurred and it provides a means of determining who was the source of infection.