World Monitor Magazine, №1/2020 WM_March 2020_FOR WEB (12.03.) | Page 44

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FiIGURE 2.
Droplet larger than aerosols, when exhaled (at velocity of
<1m/s), evaporate or fall to the ground less than 1.5 m
away. When expelled at high velocity through coughing or
sneezing, especially larger droplets (> 0.1 mm), can be car-
ried by the jet more than 2m or 6m, respectively, away.
Since the CDC provides no scientific evidence for its state-
ment that masks worn by the public “are not effective”, here
we review the scientific support for protection conferred by
surgical masks. We focus on mechanistic rationale (as op-
posed to epidemiological-phenomenological evidence). We
conclude, by considering cough droplet ballistics and the lat-
est research findings on the biology of transmission of the
SARS-CoV2 virus (which causes COVID-19) that any physi-
cal barrier, as provided even by make-shift masks, may sub-
stantially reduce the spread of COVID 19. If we are soon to
yield to the pressure to loosen lockdowns and allow limited
social interactions to revive the economy, then public masks
should have a role and could facilitate a middle-of-the-road
approach.
need not be empty: I would gladly accept a glass of water
filled to 60 % when I am thirsty. Absence of evidence (of pro-
tection) is not evidence of absence. But in our binary world,
the official message that surgical masks are “not effective”
may have sent the wrong message: that they are absolutely
useless. Sadly, with the black-and-white picture painted by
officials, the discussion about the effectiveness of masks has
been stifled, and with it the possibility of incentivizing indus-
try to ramp up production of these 75 cents-a-piece protec-
tive devices.
The official recommendation by CDC, FDA and others that
masks worn by the non-health-care professionals are ineffec-
tive is incorrect at three levels: In the logic, in the mechanics
of transmission, and in the biology of viral entry. But with the declared goal to “flatten the curve” (and not
to totally eliminate the virus) we have a “relative” as op-
posed to absolute goal, which places the notion of “partial
protection” in a new light. In principle, one could compute
the extent Y of flattening of the curve given a partial pro-
tection by X % as conferred by mask. But for that we need
to first understand the mechanics and biology of transmis-
sion in detail.
I. THE LOGIC II. THE MECHANICS
Of course no mask, be it the tight-fitting NIOSH approved
N95 respirator mask or the loosely worn surgical mask, pro-
vide perfect (“100%”) protection. But imperfect protection
does not mean “completely useless”, much as a glass not full How viruses that cause airborne diseases are carried by
droplets from person to person is a complicated, understud-
ied matter. Droplets can (for this discussion) be crudely di-
vided in two large categories based on size (FIG. 2):