In 1997, doctors at a clinic in Denmark found that one of the clinic’s long-term clients, a woman identified as GP, was HIV-positive. GP’s HIV infection was a surprise. The clinic tested her because of her symptoms — “malaise” and weight loss. But how had she been infected? GP reported no sexual partners since 1985, no blood transfusions, and no use of illegal injected drugs.
Doctors at the clinic together with outside experts investigated to find the source of GP’s infection
. They suspected she had been infected by contaminated instruments or medicines during treatment at the clinic. Beginning in 1992, the clinic had periodically given GP intravenous therapy (given her medicine through a tube and needle into a vein). Tests of GP’s stored blood found that she got HIV sometime between October 1994 and February 1996. During that time, the clinic had given her intravenous therapy 17 times.
Investigators looked at clinic records to find other patients who were HIV-positive and could have been the source of GPs infection. They found 13 patients who were HIV-positive and who had received treatment at the clinic on one or more of the 17 days that GP had received treatment. But which one — if any — was the source of the HIV that infected GP?
To identify the source of GP’s infection, the clinic sequenced HIV from GP and from the suspected source patients. [Note: Each particle of HIV is composed of thousands of small molecules or pieces. As HIV lives in a person and goes from person-to-person, some of its pieces change bit-by-bit over time. When HIV pieces, or sequences, from two people are very similar, it shows that HIV from one person somehow infected the other.]
Investigators found a match — a man identified as FDL who was known to be HIV-positive as early as 1988. FDL had received intravenous treatment in the clinic on the same day as GP during 1994-96, and his HIV was almost identical to GP’s HIV.
But how did FDL’s HIV get to GP? The clinic guessed that HIV had gone from FDL to a multi-dose vial of saline solution (salt plus water), and from the multi-dose vial to GP. When the clinic put an intravenous line (needle connected to a tube) into a patient, the health care worker first injected saline from a multi-dose vial through the line. Then the line was used to inject medicine. After the medicine was given, the health care worker again injected saline through the line. The investigators supposed that a health care worker must have injected saline into FDL’s line and then reused the syringe or needle to draw more saline from the multi-dose vial. In that way, FDL’s HIV could go from his line to the syringe and needle and from there to the multi-dose vial. From there, FDL’s HIV could get into other patients — such as GP.