Thursday, March 20, 2014

Hepatitis C Virus Infectious for Six Weeks on Surfaces?

Giant Microbes - HCV

A group of researchers from the Yale Schools of Medicine and Public Health demonstrated that hepatitis C virus (HCV) can remain infectious for up to six weeks on surfaces at room temperature. Previously, it was thought that HCV could survive for up to four days on surfaces outside the body, this new research extends that number by a month and a half

The implications of these findings are far reaching, including safety of patients and workers in healthcare settings, as well as reducing viral hepatitis transmission associated with drug use.

The study, which was funded by the National Institute on Drug Abuse (NIDA), and was designed to assess the risk of HCV transmission after infectious material dried on environmental surfaces.

This study reinforces previous findings indicating strict adherence to infection control standards and universal precautions are essential to prevent transmission of HCV in healthcare settings.

HCV has been transmitted via intravenous catheters, blood lancets, and blood glucose monitors (and now, potentially insulin pens). This new study highlights the importance of education when dealing with healthcare staff, as well as others who might come in contact with infected blood. The researchers confirmed that common commercial antiseptics (e.g. bleach, CaviCide, alcohol, etc.) reduce HCV infectiousness when used at the recommended concentrations, but not when diluted.

Brett D. Lindenbach was also a co-author on this manuscript, as he engineered the strain of HCV that was essential for the experiments. I never met Dr. Lindenbach, but I read many of his papers for my PhD, and paid close attention to his excellent work.

The HCV used for this study was Jc1/GLuc2A reporter virus. Which is an engineered virus using the chimeric genotype 2a FL-J6/JFH with a luciferase gene from Gaussia princeps (copepod) inserted between the p7 and NS2 genes.

HCV Genome - Note GLuc2A inserted between p7 and NS2 gene
2a FL-J6/JFH is a very common HCV strain used in the lab, as it is one of the only strains that replicates well enough to work with. Initially the JFH (Japanese Fulminant Hepatitis) strain was what was used, until the J6/JFH chimera was constructed, which increased the virus' replication. The luciferase gene inserted into the HCV genome is extremely useful as a way to determine infectivity or HCV presence.

If you have questions, use the comments section below! 

The authors suggest that the most likely circumstances in which healthcare workers or patients will come into contact with HCV dried on surfaces are following spillage of HCV-contaminated blood, serum, or plasma during the course of preparing blood samples for analysis or removing a venous line.

The authors simulated these types of accidents by obtaining EDTA-anticoagulated blood from HIV and HCV seronegative donors. The procedure was done twice in a biosafety cabinet where a foil mat was used to collect "accidental" drops of plasma.

To determine how quickly the plasma would dry on a surface, 24-well tissue culture plates were seeded with "accidental" drops and observed at refrigerator temperature (4 degrees Celsius), room temperature (22 degrees C), and human body temperature (37 degrees C).

24-well culture plate
Samples of plasma spiked with HCV were dropped onto the 24-well plates in a similar manner and after six weeks, Huh-7.5 cells (susceptible to HCV) were seeded in a 96-well cell culture plate, dried blood/plasma spots were rehydrated and reconstituted with culture media and then incubated with the Huh-7.5 cells. Three days later, cells were lysed and examined for luciferase (light) activity (provided by engineered HCV genome). So, if there was measurable light coming from the lysed cells (measurable by machine, not naked eye) then those cells were considered infected.

Figure 1 - A. Showing viable HCV at 40+ days at refrigerator and room temperatures
I am okay with the idea of 33ul being a droplet. I would think that is a pretty good small-average size droplet.

Overall this paper states the obvious, drops of blood or plasma containing HCV can be infectious, for how long depends on temperature, humidity, and drying as well as drop size and amount of virus contained in the drop.

It also states that common disinfectants (bleach, 70% ethanol, Cavicide) are useful, but only optimal when used at recommended concentrations, not when they are diluted.

This manuscript does have value in that it gives an upper limit to how long some of these drops could potentially remain infectious. It is a very artificial system, and I would argue using cultured cells that are specifically engineered to be susceptible to HCV infection, is not the same as exposure to a dried droplet in a clinical setting. I think six weeks is probably WAY to long to be concerned in a real-life setting.

When I was younger, I hunted a lot. I was taught to treat every gun as if it was loaded. I think it would be wise to view every drop of blood or plasma in a similar fashion, especially in the clinical or research setting.

I encourage everyone to use the comments section below! 

Lance D. Presser has a PhD in Microbiology and Immunology and currently is a Public Health Laboratorian.

Follow Lance @ldpsci

Hire Lance for any of your microbiology, virology, or public health consulting needs.

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