[Table of Contents]

Volume: 27S3 • September 2001

Viral Hepatitis and Emerging Bloodborne Pathogens in Canada

Germicide Inactivation of Hepatitis B and C Viruses*

Syed A. Sattar, Jason Tetro, V. Susan Springthorpe, Antonio Giulivi

HBV and HCV are enveloped and relatively sensitive to many physical and chemical agents. Both viruses are difficult to culture in the laboratory, and this seriously limits our understanding of their environmental survival as well as the need and choice of chemical germicides in preventing/controlling their environmental transmission. The information often quoted on the environmental stability of HBV and HCV comes from experiments in which the integrity of viral particles, antigens, nucleic acid, or enzymes was used as an indicator of the presence or absence of infectious virus. Doubtless, such approaches were justified in the absence of readily available means of detecting and quantitating such particles, but their conclusions must be interpreted very carefully. For example, when medical devices disinfected with 2% alkaline glutaraldehyde were tested for the presence of duck HBV (DHBV), PCR showed many of them to be positive, whereas no infectious virus could be detected when the same samples were injected into susceptible ducklings.

Virtually nothing is known about the environmental survival of HCV except that its RNA in plasma or serum has been found to be stable at 4^o C for 7 days⁽¹⁾. However, the stability of viral RNA should not be equated with the preservation of virus infectivity.

Relatively little is known about the inactivation of HBV and HCV by chemical germicides, and the wide variations used in working with these viruses in particular make it quite difficult to properly compare the limited data available. The findings of representative studies on HBV inactivation by chemical germicides based on the chimpanzee model have been summarized before^(2,3).

Until recently, there were no in vitro tests for the virucidal activity of chemical germicides against HCV. Bovine viral diarrhea virus (BVDV) has some properties similar to HCV and has been used in the blood product industry as a surrogate for it. HCV has been found to replicate in Vero cells without producing any cytopathic effects. Since molecular or immunologic methods can be used to detect the virus in infected cells, this opens the door for direct testing of germicides against it.

The following are specific details on the known or expected activities of major classes of chemical germicides against these two viruses and the application of such chemicals in health care. The same information is relevant to other settings where there is potential for hepatitis B and hepatitis C spread by means other than direct person-to-person contact and transfusion of tainted blood and product products.

Aldehydes

As can be seen from Table 1, formulations based on formaldehyde and glutaraldehyde can be highly effective in inactivating HBV and HCV. Recent and well-designed studies with DHBV have clearly reinforced the importance of precleaning in the chemical disinfection of heat-sensitive medical devices. As has been shown in a recent study by Chaufour et al⁽⁴⁾, decontamination even with otherwise highly effective chemicals such as glutaraldehyde can fail in the absence of proper cleaning of the devices being disinfected.

It is interesting to note that, some two decades ago, glutaraldehyde-based products were being recommended as a substitute for bleach in the decontamination of environmental surfaces. Obviously, this view is no longer relevant in view of the current safety concerns with glutaraldehyde. However, such use continues in some places.

Chlorine and iodine

Sehulster et al⁽⁵⁾ showed that exposure of Dane particles of HBV to sodium hypochlorite (5600 ppm) disrupted them and also inactivated their polymerase activity. Agolini et al⁽⁶⁾ have shown that chlorine (2500 ppm) could reduce the binding of HCV to host cells and that a contact time of at least 10 minutes was required to achieve a 91.7% cell reduction and infection. This observation needs confirmation.

No differences were found in the susceptibility of HBV and DHBV to about 3000 ppm of available chlorine as bleach or as sodium dichloroisocyanurate (NaDCC), a compound that releases chlorine on demand⁽⁷⁾.

A 1:10 dilution of domestic bleach, which contains about 5000 ppm of available chlorine, is commonly recommended for clean up of blood spills, and this level of chlorine should be considered more than adequate to deal with HBV and HCV in such blood⁽⁸⁾. However, the use of undiluted bleach (> 50,000 ppm of available chlorine) for the decontamination of shared needles and syringes⁽⁹⁾ requires review (see Decontamination of shared needles).

Experimental data on the ability of iodine-based germicides to inactivate HBV and HCV are limited, but it is expected that such products would be effective in concentrations equivalent to those of available chlorine.

Phenolics and quaternary ammonium compounds

Prince et al⁽¹⁰⁾ determined the activity of two quaternary ammonium-based products (500 and 700 ppm) as well as a phenolic (700 ppm) using a carrier test with either human HBV or DHBV. The contact time was 10 minutes at 20° C. All products proved effective against both viruses in the chimpanzee inoculation and the morphologic alteration and disintegration tests (MADT)⁽³⁾.

Agolini et al⁽⁶⁾ have also determined that subjecting HCV to a phenolic for 5 minutes effectively eliminated the ability of the virus to attach to Vero cells.

Alcohols

Ethanol and isopropanol, in the range of 70% to 80%, are effective against HBV^(11,12) and most likely against HCV as well. Therefore, alcohol-based surface disinfectants, hand rubs and pre-operative skin preparations would be expected to interrupt virus spread effectively. However, it is important to ensure adequate contact between the disinfectant and the viruses on contaminated surfaces. This may not always occur by simple wiping with alcohol. Furthermore, the presence of gross amounts of blood may interfere with the germicidal action of alcohols, in that their fixative properties may hinder the ability of alcohols to penetrate through the dried organic debris.

Peroxygen systems and gas plasma

Vickery et al⁽¹³⁾ have shown that the Sterrad system, which is based on a high concentration of vaporized hydrogen peroxide, was highly effective in inactivating DHBV even in the presence of blood as a soil load. Formulations based on stabilized hydrogen peroxide⁽¹⁴⁾ have not been tested against HBV but, on the basis of their activity against tougher organisms, such as mycobacteria and non-enveloped viruses^(14,15) , would be expected to work against it.

Smith and Pepose⁽¹⁶⁾ regard 3% hydrogen peroxide to be adequate for the inactivation of a variety of pathogens, including HCV, on tonometer prisms and trial contact lenses. It is important to note that a 3% solution of hydrogen peroxide, unless mixed with other chemicals to accelerate and potentiate its activity, is a relatively weak germicide⁽¹⁷⁾ and may require several hours of contact to be effective against susceptible organisms such as vegetative bacteria and enveloped viruses.

We are not aware of any published data on the activity of the Steris system against HBV and HCV, but it is most likely to be effective against them because of the relatively high levels of peracetic acid and temperature employed.

Gasparini et al⁽¹⁸⁾ showed that a 1% (weight per volume) solution of Virkon could destroy the surface antigen of HBV (HBsAg) with a contact time of 10 minutes. The virus challenge was a 1:30 dilution of a pool of HBsAg-positive sera. The authors suggest that the low toxicity and non-irritating nature of this product also make it a better substitute for glutaraldehyde. Similar studies have been done with the no-foam version of Virkon, and a 3% solution of the product was found to be effective against HBV in a contact time of 10 minutes⁽¹⁹⁾.

Table 1 Various means of hepatitis B and hepatitis C spread and the relevance of chemical germicides in infection control
Means of spread	Degree of relevance	Comments
Spread from infected mother to the fetus, during childbirth and/or possibly during breast-feeding Artificial insemination with semen from unscreened donors Transplantation of organs from unscreened donors Accidental exposure of healthcare personnel to needles and sharps Body contact with blood during sports such as wrestling and rugby	Very low	Germicides can play no role in preventing such spread.
Transfusion of inadequately screened blood or blood products	High	Germicides, alone or in combination with physical agents, can be used for virus inactivation in blood products.
Sharing of needles and syringes in illicit drug use Sharing of paraphernalia in using non-injectable drugs Use of contaminated needles and syringes in administering injectables Use of improperly decontaminated medical, dental and surgical devices Use of blood-containing sharps and instruments in ritual scarification, circumcision, blood-letting, tattooing, ear- and body-piercing, acupuncture, hair removal by electrolysis and sharing of shaving razors	Very high	Germicides can play a crucial role in interrupting virus spread through such means. This is especially true in the decontamination of shared needles and syringes. Although bleach is commonly recommended and used for this purpose, there is an urgent need to find an equally cheap, effective yet safer substitute for it. Such objects may pose the greatest risk when freshly contaminated; items such as toothbrushes are not meant to be shared and are also generally unsuitable for chemical disinfection; but, if items such as disposable or non-disposable shaving razors are to be shared, they must be chemically disinfected between different users.
Hemodialysis with shared equipment and in inadequately cleaned and monitored settings	Moderate	Chemical disinfection of shared hemodialysis equipment can reduce the risk of virus spread. Use of gloves and other standard precautions would be more useful than the use of chemical germicides alone for the decontamination of environmental surfaces.
Unprotected sexual contact with virus-infected individuals	Moderate	In addition to barrier protection, use of germicidal gels may reduce the risk of such spread; however, chemicals that can inactivate the viruses may not be safe for repeated long-term use.
Non-venereal contact in domestic and institutional settings with chronic carriers of HBV or HCV	Low	The vehicle(s) for such spread, which occurs predominantly in conditions of overcrowding and poor hygiene, remain(s) unidentified. Sharing of toys and items of personal use such as toothbrushes are most likely to play a role, in which case, use of germicides is unlikely to be useful in infection control.
Nosocomial and iatrogenic spread other than through the use of contaminated medical, dental and surgical devices	Low to moderate	In most settings, hands probably play a minor role in the spread of the viruses; however, regular and proper handwashing with soap and water may be sufficient to virtually eliminate the risk. Use of alcohol-based hand gels between handwashings is also considered effective; residual germicidal activity is not likely to be protective if damaged skin of hands is exposed to blood containing HBV or HCV. Any HBV or HCV on the skin surface would be readily removed/inactivated during the scrubbing procedure; however, the viruses in any leaked blood during surgery from a chronically infected surgeon's hands would most likely remain infectious. Skin antisepsis may be helpful only in situations in which the surgical site is contaminated with blood other than that of the patient.
Contact with environmental surfaces	Low to moderate	Environmental surfaces rarely act as vehicles for the two viruses, with the possible exception of those in hemodialysis units. Germicide decontamination of spills of blood and other contaminated fluids before and after their clean up forms an essential part of infection control.
Non-intact or compromised skin, e.g. chapped hands	Moderate	Topicals may play a role but proper testing is needed to confirm product potency.

Sodium hydroxide

As would be expected, 0.1 N NaOH was found to be capable of inactivating pseudorabies virus and BVDV, used as surrogates for HBV and HCV respectively, in 30 seconds at 60° C⁽²⁰⁾. Obviously, the highly corrosive nature of this procedure restricts its use to the treatment of biomedical wastes and process residues.

Acidic electrolyte water

A recent study using acidic electrolyte water has shown that a 5-minute exposure resulted in complete loss of HCV infectivity⁽²¹⁾. These observations, based on the detection of viral RNA as an indicator for the presence or absence of infectious virus, require corroboration. However, these electronically produced mixed oxidant systems may be effective at lower concentrations than single oxidant species such as chlorine.

Other types of germicidal chemicals, including topicals

The relatively low resistance of HBV and HCV to germicides tested so far indicates strongly that many properly formulated products based on a variety of chemicals may also inactivate the two viruses. These may include some novel formulations, and the advent of acceptable surrogate test systems promises to expand our understanding of HBV and HCV disinfection.

Special mention needs to be made of topical products. Widespread use of products such as chlorhexidine gluconate in infection control suggests that they should be examined for activity against HBV and HCV.

Table 1 summarizes the recognized means of HBV and HCV spread and the relative importance of chemical germicides in interrupting their transmission.

Decontamination of shared needles and syringes

There is no doubt that injecting drug users are at the greatest risk of acquiring a bloodborne infection as a result of the practice of sharing needles. At the moment, there is only one rapid and cost-effective method to interrupt the spread of bloodborne pathogens through shared needles, and that is the proper use of a germicide to disinfect them between uses. Domestic bleach is often recommended and used for this purpose⁽⁹⁾.

Disinfection of critical and semi-critical heat-sensitive medical devices

Improperly decontaminated medical devices can play a role in the spread of bloodborne pathogens, and HBV and HCV are no exception in this regard. At the same time, it must be remembered that high-level disinfectants as a class should be considered strong enough to inactivate these two viruses on such instruments with proper precleaning⁽⁴⁾.

The duck hepatitis model offers considerable promise in the evaluation of emerging products and technologies for the decontamination of HBV-contaminated medical devices. Parallel studies on HCV may not be necessary in view of the fact that it is not known to be any more resistant than HBV.

Spermicidal gels

Chemicals such as nonoxynol-9, commonly used in spermicidal gels or "invisible condoms", can produce micro-ulceration of the vaginal mucosa with prolonged use, thereby actually increasing the risk of exposure to pathogens such as HIV, HBV, and HCV. Renewed efforts are needed to find safer substitutes for such chemicals and properly test their activity against major types of sexually transmitted pathogens.

Although many of the studies cited here show successful inactivation of HBV and HCV, it must be emphasized that the test conditions often bear little resemblance to field use. The proposed surrogates offer the opportunity to examine HBV and HCV disinfection under more realistic conditions. This is particularly true for HBV using the DHBV model, as already shown by Chaufour et al⁽⁴⁾. In our view, environmental surface disinfectants to be used in most settings require no demonstrated activity or label claims against such viruses.

Manufacturers of chemical germicides must be actively discouraged from having their products tested against HBV and HCV using animals such as the chimpanzee. Label claims against such viruses may be permitted for high-level disinfectants only when the testing has been conducted using (a) a proper carrier test, (b) a suitable surrogate virus, (c) a soil load high enough to reflect that found in blood and other body fluids, (d) a contact time and product:target virus ratios commensurate with the recommended field use(s) of the product and (e) use of sufficient replicates from at least three lots of the product. The importance of proper product neutralization and other controls to make the results scientifically and statistically valid also needs to be emphasized. In the case of cell culture, it is important to show that any product residual affects neither the virus nor the virus-cell interactions, which form the basis for the assay⁽²²⁾.

Glutaraldehyde and ethylene oxide, both commonly used for decontaminating heat-sensitive medical devices, are unsafe for humans. Accidental or deliberate exposure of eyes to domestic bleach, a germicide frequently employed in the decontamination of shared disposable needles and syringes, can be quite harmful and has recently caused concerns for the safety of penitentiary staff in particular.

Manufacturers of reusable and disposable medical devices must be encouraged to work with germicide makers as well as infection control practitioners and other health care workers so that such devices can be made safer and easier to clean and disinfect. Lack of such input increases the risk of spread of infections. For example, a spring-loaded fingerstick device for blood sample collection, designed to a hold sterile and disposable lancet, was incriminated in the spread of hepatitis B because the reusable holder itself would become contaminated with blood but did not require decontamination between uses⁽²³⁾.

The continuing reports of HBV and HCV spread in hemodialysis units, even those that apparently adhere strictly to established infection control guidelines⁽²⁴⁾, require further investigation to elucidate the exact means of virus spread. Such studies should also help in better defining the need for environmental decontamination in such settings.

References

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2. Sattar SA, Tetro J, Springthorpe VS et al. Preventing the spread of hepatitis B and C viruses: Where are germicides relevant? Am J Infect Control (in press).

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6. Agolini G, Russo A, Clementi M. Effect of phenolic and chlorine disinfectants on hepatitis C virus binding and infectivity. Am J Infect Control 1999;27(3):236-39.

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22. Sattar SA, Springthorpe VS. Viricidal activity of biocides: activity against human viruses. In: Russell AD, Hugo WB, Ayliffe GAJ (eds): Principles and practice of disinfection, preservation and sterilization 3^rd edition. Oxford: Blackwell Science, 1999:168-86.

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* A full version of this article has been published in the American Journal of Infection Control: Sattar SA, Tetro J, Springthorpe VS, Giulivi A.
Preventing the spread of hepatitis B and C viruses: Where are germicides relevant? Am J Infect Control 2000;29(3):187-97.

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