This @DaringFireball post caught my eye yesterday: daringfireball.net/linked/2020/03…, and I've got some comments that I will be sharing in this tweet thread. TL;DR soap is *not* significantly more effective than alcohol-based hand sanitizers for coronavirus. (1/15)
I first heard about Thordarson (author the The Guardian article that @gruber linked) when the author of this Newsweek article newsweek.com/this-why-soap-… @kashmiragander reached out to me with some questions. (2/15)
Note that @PalliThordarson has written a couple of widely retreated threads on soap and coronavirus, based on his perspective as a perspective as a chemist. (3/15)
My attempt here is not to start a Twitter fight, but only to educate and make sure everyone is aware of all the different ways to manage risk. (4/15)
Since being quoted in the Newsweek article, I've been doing a bit of digging into the scientific literature, and I think Thordarson is off-base. (5/15)
The situation is made more complex because we don't have specific information about *this* coronavirus, but only other related enveloped viruses. (6/15)
This article on the efficacy of disinfectants against SARS coronavirus journalofhospitalinfection.com/article/S0195-… found that all four alcohol-based hand rubs led to inactivation of SARS-CoV to below the limit of detection. (7/15)
A microbiologist like me would express this as >4 or >5 log reduction. Layman's terms this means reducing 100,000 infectious virus particles to only 10 or 1, i.e. 99.99% or 99.999%. (8/15)
Here's another paper by different researchers which shows basically the same thing for World Health Organization recommended formulations against enveloped viruses including Zika, Ebola, and emerging Coronaviruses: ncbi.nlm.nih.gov/pmc/articles/P… (9/15)
The second part of the issue is "how good are soaps at inactivating enveloped viruses"? For that take a look at this article: journals.plos.org/plosone/articl…. (10/15)
Note that the PLOSone article looks at human and avian influenza viruses. They are not coronaviruses, but *are* enveloped virus. (11/15)
The authors investigated the effect of surfactants which are the main components of hand soaps. They looked at three different surfactants against two strains of influenza. (12/15)
Only one of the surfactants was able to reduce infectivity by > 4 log. The other two had a reduction of one log or less. Note that even 1 log is something (90%). (13/15)
Disclaimer: I sit on the GOJO Food Safety Advisory Board (the makers of @purell) for which I am financially compensated. These tweets were written of my own accord and without compensation. (14/15)
GOJO makes soaps *and* sanitizers, as do many other hand care companies. (15/15)
PS: you might often hear soap recommended over sanitizer in general. This is because soap is good at dislodging dirt, as well as many pathogens, including non-enveloped viruses from our skin. Sanitizer can be less effective against some other microorganisms.
