Thread by @ProfCharlesHaas

The fallacy of #fomites.
There has been a lot of attention devoted to the potential transmission of #COVID19 by fomites, a lot of money and time spent on "sanitizing" surfaces, and on marketing various chemicals, treatments, etc. 1/N

While generically, cleanliness is good, I am convinced that the vast amount of these efforts when targeted at #COVID19 are misguided and represent more #hygienetheatre than true prevention. 2/N

First, I have yet to see any reports of transmission that convincingly demonstrate a fomite route (as opposed to a couple of cases reports that allege this as a diagnosis of exclusison, while failing to consider more plausible routes such as aerosols). 3/N

Second, although there is some evidence that #SARSCOV2 when applied to various surfaces may persist for hrs to days, considering exposure pathways, the potential doses are very low. If we imagine an infected (unmasked) individual directly depositing respiratory liquid 4/N

containing virus on a surface, for another individual to be exposed there needs to be transferrence of the virus from surface to hands and then from hands to nose/mouth/eyes.

5/N

Having done a lot of #riskassessment #QMRA for fomite exposure, each of these contact opportunities results in a loss of 1-2 logs of virus. So there is 2-4 logs reduction even if the contaminated surface is touched when it is "fresh". 6/N

Much more likely to have direct large ballistic drops deposit or inhalation of smaller aerosols.
7/N

So, while surface cleaning may be beneficial for other purposes, or when there is extremely heavy contamination, in my current opinion based on available evidence, money and resources might be better applied to other routes of transmission. N/N