Hacker News Reader

Comment by mensetmanusman | Hacker News Reader

Thoughts:

Aerosol covid risk is highly likely, meaning that air travel requires N95 masks and goggles (eyes are a known vector).

If you are outdoors, dilution of virions happens quickly, especially in windy conditions. UV helps denature RNA quickly as well.

Indoor risk can be greatly mitigated with room air purifiers, but they have not been deployed because the WHO hasn’t acted on aerosol risk. (albeit, the deployment of air purifiers would be a larger expense than cloth masks, which are not effective at stopping aerosol).

View on HN

* Aerosol COVID risk is basically proven, but we don't know if it is a major mode of spread. It does seem to be related to superspreader events.

* Deployment of air purifiers would be a trivial expense relative to any other economic harms of COVID19. It's mostly a question of policy catching up to science.

* Large droplets are a confirmed major source of spread. Cloth masks help reduce those. They're not full-proof even there, but they're $2. It's a no-brainer ROI.

* Even with aerosol, the risk is reduced by cloth masks. Some aerosol comes from large droplets evaporating.

Cloth masks do a better job at preventing you from spreading COVID than they do of preventing you from catching COVID. In small confined spaces I would not want to depend on 100% mask compliance by all people to keep me safe, and I’d want a N95.

In a large, unconfined space, I would also not want to rely just on masks. It's a public health issue. If I've reduced the odds of catching COVID19 by even, say, 30%, that's an incredible impact on how much COVID19 spreads, for the cost of a $5 mask and a minor inconvenience.

The trick is to get R0 under 1, so we have exponential decline rather than exponential growth. Even if it's above 1, if we can bring the exponent down, it's huge. There's no sane argument that masks don't do that.

You might want an N95, and I might want one too, but there aren't enough to go around. For the most part, easiest thing to do is to not go out in public.

> If I've reduced the odds of catching COVID19 by even, say, 30%,

Given that the likelihood of catching it from a brief encounter with a random passer by is in fact quite small the idea that a mask could reduce the odds meaningfully in large unconfined spaces seems unlikely. We do not wear masks here in Norway but we do keep our distance (except for usual idiots at parties, etc.).

Recent clusters of infection here have all been traced to people who were in close contact with large numbers of people for hours (wedding parties, cruise ships, etc.). Then perhaps diligent use of masks might have helped but just not holding the party helps more.

> For the most part, easiest thing to do is to not go out in public.

This together with simple measures like making sure one washes ones hands seems to be what is working here.

Agreed that air travel would seem to be high-risk given airborn transmission.... but why aren't we seeing it? Seems like the easiest transmission to trace -- someone takes a plane, tests positive, contact everyone who was on the same plane. But I haven't seen a documented case over the last five months of "one person a plane infects 20 others..."

It confounds my mental model of how this virus is spread. Any idea what's going on there?

I think aircraft ventilation is designed so you have laminar flow from the ceiling to the floor. And the air filtered. Consider that people used to smoke on planes.

Please link the study showing eyes are a known vector. AFAIK we can't say one way or another. The only evidence I've seen is anecdotal from people catching it whilst using a mask. This would not be surprising if aerosol is a thing and even if not you must call into question mask quality, fit and whether the user is following necessary protocols.

Why would it not though, since there is a pathway between the eyes and the nasal cavity via the nasolacrimal duct?

Hepa filters consume the same melt-blown fiber as needed for medical n95s, though maybe by this point there is less of a shortage.

Reply on news.ycombinator.com