Very interested in the right answer here. Wikipedia says “90% alcohol rubs are more effective against viruses than most other forms of hand washing.” (And I’m hoping it will generalize to the 70% concentration I typically use.) But here’s a 2019 article that seems to show weak effectiveness against flu.
I wish I could look up the source for that 90% quote, but it’s from a book from the 1990s. Quoting a press release from ASM about that same 2019 result:
The influenza A virus (IAV) remains infectious in wet mucus from infected patients, even after being exposed to an ethanol-based disinfectant (EBD) for two full minutes… Most studies on EBDs test the disinfectants on mucus that has already dried. When he and his colleagues repeated their experiments using fully dried mucus, they found that hand rubbing inactivated the virus within 30 seconds… Washing hands with an antiseptic soap, they found, deactivated the virus within 30 seconds, regardless of whether the mucus remained wet or had dried.
Alcohol solutions containing 60%–95% alcohol are most effective, and higher concentrations are less potent because proteins are not denatured easily in the absence of water.
The tests summarized in that report suggest high efficacy at the 70% concentration for a lot of viruses, included some non-enveloped ones:
Other nonenveloped viruses such as hepatitis A and enteroviruses (e.g., poliovirus) may require 70%–80% alcohol to be reliably inactivated. However, both 70% ethanol and a 62% ethanol foam product with emollients reduced hepatitis A virus titers on whole hands or fingertips more than nonmedicated soap.
[edited to clarify]
So maybe the reason that the CDC recommends handwashing is that healthcare workers are likely to have soiled [ETA: or damp or mucus-covered] hands?
I might be misunderstanding your meanings here, so please disregard if so, but:
Quoting a press release from ASM about that same 2019 result [...]
TWiV discussed this paper a few weeks ago. I think it’s important that the finding is that virus specifically in wet mucus, not just in water generally. Mucus has complicated properties that I think are important here.
So maybe the reason that it’s recommended for healthcare workers is that they’re likely to have soiled or damp hands?
The WHO recommendation for hand sanitiser is specifically for when hands are not visibly soiled, so I don’t think it’s this.
Yeah, edited to clarify a bit. At this point I’m just a bit confused about the CDC recommendation to favour handwashing:
Wash your hands often with soap and water for at least 20 seconds, especially after going to the bathroom; before eating; and after blowing your nose, coughing, or sneezing.
If soap and water are not readily available, use an alcohol-based hand sanitizer with at least 60% alcohol. Always wash hands with soap and water if hands are visibly dirty.
Yeah, I’m also unsure about that. I tried to find some NHS guidelines as a third opinion but didn’t find any public-facing guidance directly comparing the two. The Mayo Clinic seems to weakly/obliquely recommend washing over sanitiser, but doesn’t say why and might just be copying the CDC.
I initially tried washing my hands all the time, and found that I quite quickly developed chapped and painful hands; this quickly went away after I switched to using hand sanitiser in borderline cases. So anyone who wants to follow the CDC over the WHO should make sure they have gentle soap!
Very interested in the right answer here. Wikipedia says “90% alcohol rubs are more effective against viruses than most other forms of hand washing.” (And I’m hoping it will generalize to the 70% concentration I typically use.) But here’s a 2019 article that seems to show weak effectiveness against flu.
I wish I could look up the source for that 90% quote, but it’s from a book from the 1990s. Quoting a press release from ASM about that same 2019 result:
More alcohol isn’t necessarily better- this 2002 CDC Review on Handwashing notes that:
The tests summarized in that report suggest high efficacy at the 70% concentration for a lot of viruses, included some non-enveloped ones:
[edited to clarify] So maybe the reason that the CDC recommends handwashing is that healthcare workers are likely to have soiled [ETA:
or dampor mucus-covered] hands?I might be misunderstanding your meanings here, so please disregard if so, but:
TWiV discussed this paper a few weeks ago. I think it’s important that the finding is that virus specifically in wet mucus, not just in water generally. Mucus has complicated properties that I think are important here.
The WHO recommendation for hand sanitiser is specifically for when hands are not visibly soiled, so I don’t think it’s this.
Yeah, edited to clarify a bit. At this point I’m just a bit confused about the CDC recommendation to favour handwashing:
Yeah, I’m also unsure about that. I tried to find some NHS guidelines as a third opinion but didn’t find any public-facing guidance directly comparing the two. The Mayo Clinic seems to weakly/obliquely recommend washing over sanitiser, but doesn’t say why and might just be copying the CDC.
I initially tried washing my hands all the time, and found that I quite quickly developed chapped and painful hands; this quickly went away after I switched to using hand sanitiser in borderline cases. So anyone who wants to follow the CDC over the WHO should make sure they have gentle soap!