Cooler Temperatures Enhance Survival of HIV in Syringes

The HIV virus remains alive and well in syringes containing infected blood for at least 42 days when stored in near-freezing temperatures, a study by Yale researchers shows.

Conversely, when stored above room temperature, the likelihood of encountering syringes with viable HIV-1 after one week decreases to less than one per cent, it was reported in the study.

“The practical implications of these findings are that when people do not have access to clean syringes, storing used syringes in warmer temperatures decreases the likelihood of HIV transmission,” said Robert Heimer, associate professor of epidemiology and public health at Yale School of Medicine. “Depending on the temperature, you can decrease from weeks to just one day the period of time for which syringes can spread the virus.”

He said the warmer conditions leading to HIV inactivation might include storage behind a radiator in winter or in the glove compartment of a car parked in the sun.

Published in the journal Substance Use and Misuse, the study built on earlier research at Yale showing that HIV-1 survival in syringes was strongly associated with the volume of blood remaining in the syringe and the duration of storage at room temperature.

The current study was performed to determine the effects of storage temperature upon the survival of HIV-1 inside syringes because drug injectors do not necessarily have access to climate controlled environments. The researchers loaded syringes with HIV infected blood, fully depressed the plunger to remove almost all the blood, and then stored the syringes for periods of one day to six weeks. The residual contents of the syringes were then introduced into tissue culture that allowed viable HIV to proliferate.

At 4 degrees C, 50 percent of all syringes contained viable HIV-1 at 42 days of storage, the longest storage duration tested.

At room temperature, or 20 degrees C, the last day that syringes with infected blood were positive was Day 21. Viable HIV-1 was recovered from 8 percent of these syringes.

Above room temperature, or 27, 32 and 37 degrees C, less than one percent of syringes contained viable HIV-1 after one week.

“The primary goal of our study is to understand ways to stop the spread of HIV through syringe borne transmission,” Heimer said. “Behaviors of injectors vary tremendously. Some injectors rapidly discard syringes when they are done, mostly out of fear of being spotted by police for having syringes. Improperly discarded syringes can be reused and, if contaminated with HIV, can transmit the virus.”

He said the findings that syringes can remain potentially infectious for as long as six weeks highlight a benefit of syringe exchange programs. These programs remove from circulation and possible reuse potentially infected syringes.

Syringe exchange programs transform used syringes into commodities that can be exchanged for new syringes, which are generally desired by drug injectors. In addition, syringe exchange programs can help disseminate the information about the heat-related demise of viable HIV as part of outreach efforts seeking to reduce HIV transmission among injection drug users.

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