Wednesday, November 12, 2014

Disinfecting Ebola: New Questions

I previously recommended alcohol hand rub (usually 70% ethyl or isopropyl alcohol) to kill Ebola on hands and gloves, which CDC recommends, along with soap and water.

From more reading, I no longer feel this is adequate, as it appears alcohol has not been tested on Ebola, and because other environmental tests have found Ebola to be hardier than one would have guessed (see Canadian discussion below). 

According to the manufacturer of a popular brand of alcohol hand sanitizer, Purell:

Ebola viruses are high risk pathogens that must be contained and are not readily available for laboratory testing. As of today, we are not aware of any hand sanitizers that have been tested against Ebola viruses, including PURELL® Hand Sanitizer. However, it is important to note that the Ebola virus is an enveloped virus. Enveloped viruses in general are easily killed or inactivated by alcohol. World Health Organization (WHO) and the Center for Disease Control and Prevention (CDC) are recommending handwashing and the use of alcohol-based hand sanitizer as a preventive measure during this outbreak.
As we have already noted, CDC speaks with forked tongue on Ebola, presumably because of the imperative to appear fully prepared, when it isn't. The following CDC document, which discusses how to decontaminate surfaces (not skin), admits that although Ebola is an enveloped virus, it may require stronger measures for decontamination than the enveloped viruses we are used to dealing with in hospitals.  Instead, CDC recommends we treat Ebola like we would treat Norovirus, which is not killed with alcohol rub.  
  • Use a U.S. Environmental Protection Agency (EPA)-registered hospital disinfectant with a label claim for a non-enveloped virus (e.g., norovirus, rotavirus, adenovirus, poliovirus) to disinfect environmental surfaces in rooms of patients with suspected or confirmed Ebola virus infection. Although there are no products with specific label claims against the Ebola virus, enveloped viruses such as Ebola are susceptible to a broad range of hospital disinfectants used to disinfect hard, non-porous surfaces. In contrast, non-enveloped viruses are more resistant to disinfectants. As a precaution, selection of a disinfectant product with a higher potency than what is normally required for an enveloped virus is being recommended at this time. EPA-registered hospital disinfectants with label claims against non-enveloped viruses (e.g., norovirus, rotavirus, adenovirus, poliovirus) are broadly antiviral and capable of inactivating both enveloped and non-enveloped viruses...
  •  For large spills, a chemical disinfectant with sufficient potency is needed to overcome the tendency of proteins in blood and other body substances to neutralize the disinfectant's active ingredient. An EPA-registered hospital disinfectant with label claims for non-enveloped viruses (e.g., norovirus, rotavirus, adenovirus, poliovirus) and instructions for cleaning and decontaminating surfaces or objects soiled with blood or body fluids should be used according to those instructions.
CDC also recommends sodium hypochlorite "wipes" for cleaning collections of infectious fluids. This may not be adequate either.

"Wipes" are convenient because they usually do not drip, or splash, which could spread viral contamination.  However, virus is killed as a function of the amount and concentration of the active ingredient, the concentration of virus, and the amount of time the two are in contact, as well as interfering substances that may be present.  Simply wiping a surface will not necessarily inactivate all virus on the surface. Nor will a quick spraying when the active ingredient evaporates rapidly.

The Canadian public health agency emphasizes that time is needed to kill the virus, not simply contact with a disinfectant that rapidly evaporates, like alcohol. Their guidance says the following:

"SUSCEPTIBILITY TO DISINFECTANTS: Ebolavirus is susceptible to 3% acetic acid, 1% glutaraldehyde, alcohol-based products, and dilutions (1:10-1:100 for ≥10 minutes) of 5.25% household bleach (sodium hypochlorite), and calcium hypochlorite (bleach powder) 
Footnote49 Footnote50 Footnote62 Footnote63. The WHO recommendations for cleaning up spills of blood or body fluids suggest flooding the area with a 1:10 dilutions of 5.25% household bleach for 10 minutes for surfaces that can tolerate stronger bleach solutions (e.g., cement, metal) Footnote62. For surfaces that may corrode or discolour, they recommend careful cleaning to remove visible stains followed by contact with a 1:100 dilution of 5.25% household bleach for more than 10 minutes.
PHYSICAL INACTIVATION: Ebola are moderately thermolabile and can be inactivated by heating for 30 minutes to 60 minutes at 60°C, boiling for 5 minutes, or gamma irradiation (1.2 x106 rads to 1.27 x106 rads) combined with 1% glutaraldehyde Footnote10 Footnote48 Footnote50. Ebolavirus has also been determined to be moderately sensitive to UVC radiation Footnote51.
SURVIVAL OUTSIDE HOST: Filoviruses have been reported capable to survive for weeks in blood and can also survive on contaminated surfaces, particularly at low temperatures (4°C)Footnote52 Footnote61. One study could not recover any Ebolavirus from experimentally contaminated surfaces (plastic, metal or glass) at room temperature Footnote61.  In another study, Ebolavirus dried onto glass, polymeric silicone rubber, or painted aluminum alloy is able to survive in the dark for several hours under ambient conditions (between 20°C and 25°C and 30–40% relative humidity) (amount of virus reduced to 37% after 15.4 hours), but is less stable than some other viral hemorrhagic fevers (Lassa) Footnote53. When dried in tissue culture media onto glass and stored at 4 °C, Zaire ebolavirus survived for over 50 days Footnote61. This information is based on experimental findings only and not based on observations in nature. This information is intended to be used to support local risk assessments in a laboratory setting.
A study on transmission of ebolavirus from fomites in an isolation ward concludes that the risk of transmission is low when recommended infection control guidelines for viral hemorrhagic fevers are followed Footnote64. Infection control protocols included decontamination of floors with 0.5% bleach daily and decontamination of visibly contaminated surfaces with 0.05% bleach as necessary...
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply suitable disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean-up.
DISPOSAL: Decontaminate all materials for disposal from the containment laboratory by steam sterilisation, chemical disinfection, incineration or by gaseous methods. Contaminated materials include both liquid and solid wastes.
STORAGE: In sealed, leak-proof containers that are appropriately labelled and locked in a Containment Level 4 laboratory."
Of course, the obvious question is why hasn't CDC or EPA or OSHA or DOD tested Ebola against all usual/available disinfectants so we do not have to guess.  Can Sanjay or another TV doc find out for us?

UPDATE Nov 21:  Today CDC posted a document on disinfecting Ebola.  Ignore it; it is confusing and wrong. In 2 places it says Ebola is an enveloped virus, and these are usually very susceptible to disinfection. However, the document says to use agents labelled by EPA for non-enveloped viruses, which are harder to kill.  CDC lists a number of disinfecting agents, but fails to note that to kill Ebola virus they need to be in contact with it for specified times.

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