Infection Control

 

Hepatitis C Virus Maintains Infectivity for Weeks after Drying on Inanimate Surfaces at Room Temperature: Implications for Risks of Transmission

 
 

Hepatitis C Virus Maintains Infectivity for Weeks after Drying on Inanimate Surfaces at Room Temperature: Implications for Risks of Transmission
Journal of Infectious Diseases


"In our simulation of real world risks of HCV transmission in settings conducive to exposure to HCV-contaminated fomites, we observed that HCV could maintain infectivity for up to 6 weeks at 4° and 22°C…...the commercially available antiseptics reduced the infectivity of HCV on surfaces only when used at the recommended concentrations 25,27, but not when further diluted…...Almost 100% of the contaminated spots stored at 4° and 22°C remained positive for HCV through three weeks of storage (Figure 2A). At 37°C, 100% of the spots were positive till 10 days of storage and then declined to 40% and 0% at days 14 and 21…..After 1 min exposure to bleach (1:10 dilution), cavicide (1:10), and ethanol (70%), the percentage of positive contaminated HCVcc spots were 0%, 3 ± 6%, and 13 ± 6%,      respectively (Figure 3B)."

 

"This finding supports our hypothesis that the increasing incidence of nosocomial HCV infections may be due to accidental contact with HCV-contaminated fomites and other hospital equipment even after prolonged periods following their deposition. Moreover, we found that HCV infectivity was influenced by HCV viral titer and the temperature and humidity of the storage environment. Furthermore, the commercially available antiseptics reduced the infectivity of HCV on surfaces only when used at the recommended concentrations 25,27, but not when further diluted."

 

"The fact that under these conditions we found HCV to be infectious for up to 6 weeks, consistent with our previous report that HCV survived in tuberculin syringes for up to 63 days 20, is of public health concern. Taken together, these studies show that HCVcc remains potentially infectious for prolonged periods of time, ranging from 16 hours to 6 weeks depending on the assay system.'

 

"Finally, given the infection control implications of our findings, we decided to investigate if commonly used antiseptics are effective against HCV. We demonstrated that bleach, cavicide, and ethanol are effective at their recommended concentrations 25-27.

It is possible that the efficacy of cavicide at 1:10 is overestimated because the disinfectant itself reduced host cell viability by 70%. Further dilution of each antiseptic proved suboptimal

(Figures 3B and C). The finding for ethanol paralleled that of Ciesek et al., who found that HCV titers decreased at concentrations of 30% and 40% but complete inactivation did not occur at an exposure time of 5 min29. However, undiluted concentrations of several hand antiseptics (based on povidone-iodine, chlorhexidine digluconate, and triclosan) reduced HCV infectivity to undetectable levels 29. Thus, there are several commercially available antiseptics that are effective against HCV.

 

Finally, given the infection control implications of our findings, we decided to investigate if commonly used antiseptics are effective against HCV. We demonstrated that bleach, cavicide, and ethanol are effective at their recommended concentrations 25-27. It is possible that the efficacy of cavicide at 1:10 is overestimated because the disinfectant itself reduced host cell viability by 70%. Further dilution of each antiseptic proved suboptimal (Figures 3B and C). The finding for ethanol paralleled that of Ciesek et al., who found that HCV titers decreased at concentrations of 30% and 40% but complete inactivation did not occur at an exposure time of 5 min29. However, undiluted concentrations of several hand antiseptics (based on povidone-iodine, chlorhexidine digluconate, and triclosan) reduced HCV infectivity to undetectable levels 29. Thus, there are several commercially available antiseptics that are effective against HCV.

 

Our study, which sought to improve upon prior studies, still has some limitations.

First, the assay employs a genetically modified HCV laboratory clone derived from a genotype 2a virus that may not reflect survival characteristics of human isolates.

However, the thermostability pattern of our virus is similar to that of other genotypes 32.

Second, the spiking of HCV-seronegative blood might not sufficiently replicate the biological factors present in the blood of HCV-infected individuals that could moderate

HCV transmission and infectivity. However, the consistency of our results with previous

in vitro studies and epidemiologic studies reporting transmission of HCV in healthcare setting and through sharing of injection paraphernalia39-43 support our findings.

 

In conclusion, we have demonstrated that HCVcc can remain infectious at room temperature for up to 6 weeks. Our hypothesis of potential transmission from fomites was supported by the experimental results and provides the biological basis for recent observational studies reporting increasing incidence of nosocomial HCV infections and continued high incidence among people who inject drugs.”