
Covid-19 outbreak associated with air conditioning in restaurant in Guangzhou - rsecora
https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article
======
CrazyStat
Title is misleading. This is an article in a journal published by the CDC, not
a statement by the CDC.

The evidence that the air conditioning was responsible is circumstantial at
best, and I'm somewhat skeptical. If the index patient had been located at
Table C then I would find the claim more credible, but they're claiming the
air conditioner both pushed aerosolized droplets away and pulled them toward
it. According to the figure the other air conditioner circulates air over a
large diffuse area covering 9-10 tables, but the air conditioner in question
magically only covers 3 tables and E and F get no air circulation or
something. It seems like the air circulation pattern is drawn to fit the
hypothesis rather than based on any principled analysis.

They entirely ignore other possibilities like "someone from Table C walked
past Table B on their way to the bathroom/stairs/whatever, and the index
patient at Table B coughed around that time."

~~~
maxerickson
Typically, in this context, 'aerosolized' means that the virus is persistent
in the air. Droplet is different, it doesn't persist.

Also, much of the point of the article is to bring attention to the
circumstantial evidence.

------
glofish
If you read the paper it turns out there is no actual evidence for the Air
Conditioning route other than "the airflow direction"

As a matter of fact "air conditioning" is not even involved, the same airflow
could be just as well caused by a fan or the waiters moving about carrying the
air around them.

It is ridiculously sloppy.

~~~
LorenPechtel
Yeah. The 6' safety distance applies to non-moving situations. If you have
either moving people (you need more than 6' when following someone moving at a
decent pace) or airflow (wind or air conditioners) it changes. This should be
obvious, the only reason for research would be to figure out how much it
increases the needed distance.

~~~
bookofjoe
[http://www.urbanphysics.net/COVID19_Aero_Paper.pdf](http://www.urbanphysics.net/COVID19_Aero_Paper.pdf)

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erynvorn
Spending one hour in a small restaurant room without windows sitting next to a
family who just escaped from Wuhan on January 24th is the reason for the
contagion, not any AC issue. Bad title. Astute but useless study by the CDC.

~~~
forgingahead
I agree with your comment, but how does "astute and useless" go together?

~~~
SilasX
Astute + useless = pedantic.

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bricss
How about a bit better title? - "COVID-19 Outbreak Associated with airlines
and public transportation to Restaurant(s)"

------
Zenst
Not surprising as many air conditioning units don't filter the air at the
level required to remove viral agents.

Also been reports about them and virus's in the past.

But more recently [https://www.telegraph.co.uk/news/2020/03/06/air-
conditioning...](https://www.telegraph.co.uk/news/2020/03/06/air-conditioning-
systems-could-spread-coronavirus-research-shows/)

But like many things, even common sense needs the data to back it up so people
take note.

Coz we have had experts in the field of air-con say they don't, and also
experts say they do:

[https://www.straitstimes.com/singapore/health/coronavirus-
tu...](https://www.straitstimes.com/singapore/health/coronavirus-turn-off-air-
conditioners-and-open-windows-to-reduce-risk-of-being)

~~~
chiph
Office buildings I've worked at in the past barely had any filtration. Within
a few days, the untouched parts of your desk would have a layer of dust on it.
I'm now (well, not _now_ -now since everyone is WFH) in a LEED Gold building
and the filtration is much better, and I only have to clean the monitors every
5 or 6 weeks.

As good as it is, it still won't catch virus sized particles - that's a
biosafety level 3 or 4 facility (like in _Andromeda Strain_ ) and you're not
going to find that in an commercial building.

~~~
JshWright
Coronavirus requires droplets to spread. Those droplets can be very small, and
carry a ways through the air (which is what this article is proposing, not
that the virus was carried through the ducting), but they are orders of
magnitude bigger than the virus itself, and would absolutely be caught by a
typical filter.

There are viruses that can spread that way. Measles, for instance, is known
for doing that. Coronavirus can't (as far as anyone knows, and we know quite a
lot about that).

------
roenxi
Gotta wonder at who the specialists are who deal with this sort of thing and
where they come from. They'd need a complicated background of medicine crossed
with physics or engineering. It seems like an obviously useful thing to
specialise in so they must have a few in-house experts but it seems unlikely
that a medical background would prepare people for modeling the motion of
small water droplets in air. That sort of thing isn't necessarily hard but it
also isn't trivial.

------
gregoriol
This "airstream" study is really interesting as it could change much of the
response and protection put in place in the next few months.

Another thing interesting to study would be how it spread on the cruise ships.

------
MilnerRoute
Wouldn't it be more accurate if the headline said "A Covid-19 outbreak..."

As it's written, it sort of sounds like it's implying the global pandemic was
the fault of a restaurant air conditioner.

------
londons_explore
My personal hypothesis is nearly all (ie. 99%) of infections are via
aerosolised droplets, and none or nearly no infections via surfaces or lack of
hand washing.

Looking at XRays of lung tissue showing clear infection hotspots suggesting
the infection has been breathed in, rather than come via the bloodstream
(which would typically cause the whole lung to get infected at roughly the
same time).

The fact that disease transmission has been dramatically slowed in places
implementing facemask requirements backs this up.

If only we could collect more reliable data confirming or denying the above
hypothesis, and we managed to confirm it, then simply saying "you must wear a
mask at all times outside your house" would probably allow lifting all other
disease spread measures.

~~~
ekianjo
> Looking at XRays of lung tissue showing clear infection hotspots suggesting
> the infection has been breathed in, rather than come via the bloodstream
> (which would typically cause the whole lung to get infected at roughly the
> same time).

Poor argument, since most infected people are apparently asymptomatic, so what
you see on X-ray are cherry-picked worst cases, not representative of the
infection as a whole.

This being said, your hunch may be right, but so far there are still many
things we don't understand clearly about how the infection occurs.

------
meddlepal
Do Chinese not kiss and hug as a greeting for close family? It seems far more
likely that it happened that way than air-borne droplets dispersed via AC.

~~~
jfoster
> On January 23, 2020, family A traveled from Wuhan and arrived in Guangzhou.
> On January 24, the index case-patient (patient A1) ate lunch with 3 other
> family members (A2–A4) at restaurant X. Two other families, B and C, sat at
> neighboring tables at the same restaurant.

Three families, not one.

