Research Spotlight: Destruction of human norovirus on copper alloy surfaces – NoroCORE Food Virology

Research Spotlight: Destruction of human norovirus on copper alloy surfaces

Copper sheets used in the experimentsWe are proud of all of our NoroCORE students, and here we highlight a recently published study performed by Clyde Manuel and Matthew Moore in the Jaykus lab here at NCSU, on the effects of copper alloys on the human norovirus. This work was also just featured by the American Society for Microbiology, and these two PhD students also got first place in the Developing Scientist Competition at the last IAFP conference!

There has been a good deal of research in the past few years on the antimicrobial properties of copper (here’s a handy review article), and you may have heard about the prospect of using copper doorknobs in hospitals and other places that are often touched. Clyde and Matthew’s work is the first time copper’s impacts on the human norovirus have been studied.

In a nutshell, they used small sheets of five different copper alloys that had 61 to 100% copper content, as well as stainless steel as a control, which is also the classic metal of choice in medical facilities. Samples of human stool containing a GII.4 norovirus (the type most often responsible for norovirus outbreaks worldwide) or GII.4 virus-like particles (VLPs) were deposited on the different metals. (VLPs are structurally identical to the virus capsid, which is the outer protein coating that protects the viral genome, but they lack the genome inside. VLPs are particularly useful for norovirus research since we cannot yet culture the actual virus.) The researchers then looked at virus survival at set intervals (0, 15, 30, 60, 120, and 240 minutes). They used RT-qPCR to assess the integrity of the viral genome, and several methods to assess capsid integrity (specifically RT-qPCR, transmission electron microscopy, Western blot, and a histo-blood group antigen (HBGA) binding assay).

Based on their findings, it appears that both the viral genome and its capsid are being damaged in the face of copper, also rendering the virus unable to bind to our HBGA receptors. When the viral particles in the stool samples were exposed to pure copper for an hour, there was approximately a 3 to 4 log10 reduction in the number of viral genomes detected. (To put it into perspective, that may not be as effective as a strong bleach solution, but there are disinfectants out there that are thought to be similarly effective, or even less effective.) The level of destruction of viral particles corresponded to increasing copper content, and virtually no change was seen on the stainless steel after four hours.

One really neat finding is that when viewed on transmission electron microscopy, the VLPs went from being evenly scattered across the viewing area at the beginning, to being clumped together after about an hour, ultimately becoming an indiscernible field of debris at four hours, while nothing changed on the stainless steel.

There are too many cool findings in the paper to list here, so why not read it for yourself?

Manuel, CS, Moore, MD, Jaykus, LA. 2015. Destruction of the Capsid and Genome of GII.4 Human Norovirus Occurs During Exposure to Metal Alloys Containing Copper. Appl. Environ. Microbiol. [Epub ahead of print].

There are many potential applications of this research, notably for areas we frequently touch, such as doorknobs, handrails, and buttons. In addition to healthcare facilities, copper alloys could be useful in other public and populated areas, such as schools, cruise ships, and eldercare facilities.

Great work guys!

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