Inactivation of HCV and HIV by microwave: a novel approach for prevention of virus transmission among people who inject drugs

Across the world about 80 million people are estimated to be chronically infected with Hepatitis C virus (HCV). Chronic infection of liver cells, called hepatocytes, can cause serious long-term health risks such as liver degeneration, or cirrhosis, and even cancers, such as hepatocellular carcinoma. HCV death rates have surpassed AIDS related deaths in recent years, motivating researchers to explore novel therapy options, as a vaccine for HCV still does not exist. One population of at risk individuals and infected persons that exists within middle and higher income countries such as the United States, is people who inject drugs. It is estimated that 50-80% of HCV infections in these countries occur in intravenous drug users, which adds up to about 10 million people worldwide. Similarly, because HIV-1 infection is also spread through shared intravenous drug paraphernalia use, it is estimated the 20-30% of HIV-1 infected persons are coinfected with HCV. Because of HIV’s effect on the body’s immune system, coinfected individuals are at a higher risk for the development of the deadly complications of HCV.

In light of recent focus on domestic drug abuse and the heroin epidemic, it is very important that research target new ways to prevent the spread of infection in a growing population of people who inject drugs. While prevention strategies, such as needle or syringe exchange programs and opioid substitution therapy do exist, HCV infection rates have not fully been managed. Previous work by researchers at the Institute of Experimental Virology, in conjunction with many other research institutes, has shown that all genotypes of HCV are temperature sensitive. Using this concept, researchers tested the ability of microwaves, the house hold appliance used to heat foods and liquids, to affect the infectivity of HCV and HIV-1 separately, upon co-infection, and when found on drug paraphernalia.

The main findings of this study show that the infectivity all HCV genotypes is significantly reduced in cell culture, on contaminated syringes, in contaminated syringe filters, and in cultures co-infected with HIV-1. The reduction of infectivity is owed to temperature dependent degradation of the viral envelope and RNA. Researchers exposed the HCV treated solutions to microwave irradiation at intervals of 1, 2, and 3 minutes at various wattages between 90 and 800 W. It was found from analysis of the collected data points that upon reaching a critical temperature of between 56-60 °C, infectivity of the HCV particles was reduced by 90%. This corresponds to 2 minutes of irradiation at a minimum of 360 W. Importantly, it was found that HIV-1 particles also significantly lost infectivity upon being microwaved alone or in the presence of HCV. Syringes contaminated with HIV and HCV were tested with microwave irradiation for 3 minutes at various levels of wattage. The test showed again that at 360 W, both viruses displayed significantly reduced infectivity. Finally, researches tested drug preparation filters, which capable of supporting virus survival for up to two days and are often reused by intravenous drug users. To make the tests more realistic, filters were used to filter actual street heroin before being microwaved. In accordance with the previous findings, irradiation of drug filters for a minimum of 2 minutes at a minimum of 360 W caused significant reduction in viral infectivity.

Stability of HCV and/or HIV-1 after microwave irradiation. Viral titers were significantly decreased in suspensions subject to microwave irradiation above above 360 W for both HCV and HIV-1. 

The purpose of this study was to determine the parameters of a new mode of reducing the spread HCV infection among intravenous drug users, specifically microwave irradiation. This population, which mainly consists of people in middle and upper income countries, is at risk of HCV infection, reinfection after treatment, and coinfection with HIV-1 due to transmission through contaminated syringes and paraphernalia. The research presents a relatively simple solution to prevent infection with a few key advantages, namely ease of procedure, accessibility, and safety both for users and their drugs. Because microwaves are available in most households, and are simple to use they offer an attractive and easy method of ensuring sanitary conditions for intravenous drug use. Because of the high melting temperature of heroin and cocaine, drug users need not fear harming their product while sterilizing their equipment. This method, however, is not without draw back. Because metal cannot be microwaved safely, the needle portion of syringes cannot be decontaminated of HCV or HIV-1. This poses a major drawback for this method as a stand-alone solution for controlling viral spread, however in conjunction with needle exchange programs that are already established, the microwave method could prove very effective as a mode of antiviral therapy. Moving forward, researchers should focus of simple household methods of disinfecting the needles to ensure that people who inject drugs can quickly and safely reduce the infectivity of viral pathogens such as HCV and HIV-1.

Source Paper: Siddharta, A. et al. Inactivation of HCV and HIV by microwave: a novel approach for prevention of virus transmission among people who inject drugs. Sci. Rep. 6, 36619; doi: 10.1038/srep36619 (2016).

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Figures were taken directly from source paper.